Effects of weight loss on changes in insulin sensitivity and lipid concentrations in premenopausal African American and white women

Effects of energy-restricted diets with or without nuts on weight, body composition and glycaemic control in adults: a scoping review

Energy-restricted (ER) diets promote weight loss and improve body composition and glycaemic control. Nut consumption also improves these parameters. However, less is known about the combined benefit of these two strategies. This scoping review implemented a systematic search of Medline, Embase and Scopus to identify randomised controlled trials evaluating the effect of ER diets with or without nuts on body mass, body composition and glycaemic control in adults. After reviewing titles and abstracts, twenty-nine full-text articles were screened, resulting in seven studies reported in eight papers that met the inclusion criteria. Energy restriction was achieved by prescribing a set energy target or reducing intake by 1000-4200 kJ from daily energy requirements. Interventions ranged from 4 to 52 weeks in duration and contained 42-84 g/d of almonds, peanuts, pistachios or walnuts. While all studies reported that energy restriction resulted in significant weight loss, the addition of nuts to ER diets demonstrated significantly greater weight loss in only approximately half of the included studies (4/7 studies). There was limited evidence to support additional benefits from nuts for body composition measures or glycaemic control. Although improvements in weight loss and glycaemia were not consistent when nuts were included in ER diets, no study revealed an adverse effect of nut consumption on health outcomes. Future studies could explore the effect of consuming different types and amounts of nuts, combined with various levels of energy restriction on weight, body composition and glycaemic control.

Association of Obesity With Type 2 Diabetes Mellitus: A Hospital-Based Unmatched Case-Control Study

Background The prevalence of type 2 diabetes mellitus (T2DM) and obesity is alarmingly increasing with the accessibility of the modern lifestyle. This study aimed to assess the association of obesity with T2DM among the patients visiting the Medicine Department of Ayub Teaching Hospital, Abbottabad, Pakistan. Method This hospital-based, unmatched case-control study was conducted from March 2022 to September 2022. A total of 200 patients (age ≥ 18) (100 cases and 100 controls) were recruited. Those patients with a history of T2DM were selected as cases, and those without diabetes were selected as controls after taking informed written consent. Patients with BMI ≥ 25 were considered obese. Data were collected through a non-probability convenience sampling technique using a self-structured non-validated questionnaire. Data were organized and analyzed through IBM SPSS Statistics for Windows, version 26.0 (IBM Corp., Armonk, NY). Results We found a significant positive association of obesity with T2DM with a crude odds ratio of 3.6 (95% CI: 2.0-6.6), a p-value of 0.000, and an adjusted odd ratio of 3.7 (95% CI: 1.9 - 7.1), with a p-value of 0.004 (adjusted for potential confounders, including gender, age group, stress, and status of physical activeness) using a logistic regression model. Conclusion It is concluded that obesity is strongly associated with developing T2DM and lack of physical activity, people over 45 years, and males with obesity have a higher chance of developing T2DM.

Early-Adulthood Weight Change and Later Physical Activity in Relation to Cardiovascular and All-Cause Mortality: NHANES 1999-2014

Limited evidence investigated the combined influence of early-adulthood weight change and later physical activity on the risk of cardiovascular (CVD) and all-cause mortality. The aim of this study is to explore the associations of early-adulthood weight change and later physical activity with CVD and all-cause mortality. This is a cohort study of 23,193 US adults aged 40 to 85 years from the National Health and Nutrition Examination Survey (NHANES) 1999 to 2014. Cox proportional hazards regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) of CVD and all-cause mortality associated with early-adulthood weight change and later physical activity. During a median follow-up of 9.2 years, there were 533 and 2734 cases of CVD and all-cause deaths. Compared with being physically inactive, the HRs of the CVD mortality of being physically active were 0.44 (0.26 to 0.73), 0.58 (0.19 to 1.82), 0.38 (0.17 to 0.86) and 0.46 (0.21 to 1.02) among individuals with stable normal, stable obese, non-obese to obese and maximum overweight early-adulthood weight change patterns. Using stable normal patterns that were physically active later as the reference, other early-adulthood weight change patterns did not show a significantly higher risk of CVD mortality when participants were physically active in later life; later physically inactive participants had a significantly increased risk of CVD mortality, with HRs of 2.17 (1.30 to 3.63), 5.32 (2.51 to 11.28), 2.59 (1.29 to 5.18) and 2.63 (1.32 to 5.26) in the stable normal, stable obese, non-obese to obese and maximum overweight groups, respectively. Similar results can be seen in the analyses for all-cause mortality. Our findings suggest that inadequate physical activity worsens the negative impact of unhealthy early-adulthood weight change patterns, which is worthy of being noted in the improvement of public health.

Comparisons of calorie restriction and structured exercise on reductions in visceral and abdominal subcutaneous adipose tissue: a systematic review

Exercise and low-calorie diets are common approaches taken to produce an energy deficit for weight loss in obesity. Changes in visceral and abdominal subcutaneous fat associated with weight loss are important questions but have not yet been concluded. We investigated the relationship between changes in visceral (VAT) and subcutaneous adipose tissue (SAT) areas obtained by abdominal imaging with the change in total body fat. The relevant databases were searched through January 2021 according to the PRISMA guidelines. Sixty-five studies were included. We found that the change in total body fat was associated with changes in both VAT and abdominal SAT areas, but the relationship between total body fat and the abdominal SAT area appeared stronger. Baseline values of VAT and abdominal SAT area were similar in the three treatment groups (calorie restriction, calorie restriction plus exercise, and exercise alone). The reduction in abdominal SAT area for a loss of 1 kg of total body fat was about 10 cm², which was similar among all the treatments. The change in VAT area (-26.3 cm²) was a similar level as the change in abdominal SAT area (-31.5 cm²) in the exercise, whereas in the calorie restriction with and without exercise, the change in VAT area (-33.6 and -51.6 cm², respectively) was approximately half of the reduction of SAT area (-65.1 and -87.2 cm², respectively). Absolute changes in VAT and abdominal SAT areas might differ between interventions for the exercise and calorie restriction with and without exercise.

Obesity in African-Americans: The role of physiology

The disproportionate obesity in African American (AA) women has a physiologic basis and can be explained by the interactive effects of insulin secretion, insulin clearance, insulin sensitivity and the glycaemic load of the diet. This review will present data supporting a physiologic basis for obesity propensity in obesity-prone AA women that resides in their unique metabolic/endocrine phenotype: high beta-cell responsiveness, low hepatic insulin extraction and relatively high insulin sensitivity, which together result in a high exposure of tissues and organs to insulin. When combined with a high-glycaemic (HG) diet (that stimulates insulin secretion), this underlying propensity to obesity becomes manifest, as ingested calories are diverted from energy production to storage. Our data indicate that both weight loss and weight loss maintenance are optimized with low-glycaemic (LG) vs HG diet in AA. Whether greater obesity in AA is mechanistically related to their greater prevalence of type 2 diabetes is debatable. This review provides data indicating that obesity is not strongly related to insulin resistance in AA. Rather, insulin resistance in AA is associated with relatively low adipose tissue in the leg, consistent with a genetic predisposition to impaired lipid storage. Greater bioenergetic efficiency has been reported in AA and, via resultant oxidative damage, could plausibly contribute to insulin resistance. In summary, it is proposed here that a subset of AA women are predisposed to obesity due to a specific metabolic/endocrine phenotype. However, greater diabetes risk in AA has an independent aetiology based on impaired lipid storage and mitochondrial efficiency/oxidative stress.

Insulin resistance contributes to racial disparities in breast cancer prognosis in US women

Background

Racial disparities in breast cancer survival between Black and White women persist across all stages of breast cancer. The metabolic syndrome (MetS) of insulin resistance disproportionately affects more Black than White women. It has not been discerned if insulin resistance mediates the link between race and poor prognosis in breast cancer. We aimed to determine whether insulin resistance mediates in part the association between race and breast cancer prognosis, and if insulin receptor (IR) and insulin-like growth factor receptor (IGF-1R) expression differs between tumors from Black and White women.

Methods

We conducted a cross-sectional, multi-center study across ten hospitals. Self-identified Black women and White women with newly diagnosed invasive breast cancer were recruited. The primary outcome was to determine if insulin resistance, which was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR), mediated the effect of race on prognosis using the multivariate linear mediation model. Demographic data, anthropometric measurements, and fasting blood were collected. Poor prognosis was defined as a Nottingham Prognostic Index (NPI) > 4.4. Breast cancer pathology specimens were evaluated for IR and IGF-1R expression by immunohistochemistry (IHC).

Results

Five hundred fifteen women were recruited (83% White, 17% Black). The MetS was more prevalent in Black women than in White women (40% vs 20%, p < 0.0001). HOMA-IR was higher in Black women than in White women (1.9 ± 1.2 vs 1.3 ± 1.4, p = 0.0005). Poor breast cancer prognosis was more prevalent in Black women than in White women (28% vs 15%. p = 0.004). HOMA-IR was positively associated with NPI score (r = 0.1, p = 0.02). The mediation model, adjusted for age, revealed that HOMA-IR significantly mediated the association between Black race and poor prognosis (β = 0.04, 95% CI 0.005–0.009, p = 0.002). IR expression was higher in tumors from Black women than in those from White women (79% vs 52%, p = 0.004), and greater IR/IGF-1R ratio was also associated with higher NPI score (IR/IGF-1R >  1: 4.2 ± 0.8 vs IR/IGF-1R = 1: 3.9 ± 0.8 vs IR/IGF-1R < 1: 3.5 ± 1.0, p < 0.0001).

Conclusions

In this multi-center, cross-sectional study of US women with newly diagnosed invasive breast cancer, insulin resistance is one factor mediating part of the association between race and poor prognosis in breast cancer.

Race affects the association of obesity measures with insulin sensitivity

BACKGROUND

Race differences in body composition and fat distribution may in part explain the differences in insulin sensitivity and the disproportionate burden of type 2 diabetes in African Americans.

OBJECTIVE

To determine if differences in body composition and fat distribution explain race differences in insulin sensitivity and identify obesity measures that were independently associated with insulin sensitivity.

METHODS

Participants were 113 lean, overweight, and obese African-American and Caucasian-American adults without diabetes. Skeletal muscle insulin sensitivity was determined using a hyperinsulinemic-euglycemic clamp (SIClamp, insulin rate:120 mU/m2/min). Subcutaneous abdominal adipose tissue (SAAT), intra-abdominal adipose tissue (IAAT), and liver fat were measured by MRI; leg fat, total fat, and lean mass were measured by DXA.

RESULTS

Race-by-adiposity interactions were significant in cross-sectional analyses utilizing multiple linear regression models for SIClamp (P < 0.05); higher BMI, fat mass, SAAT, leg fat, and liver fat were associated with lower SIClamp in Caucasian Americans but not African Americans. Race-by-IAAT interaction was not significant (P = 0.65). A central fat distribution (SAAT adjusted for leg fat) was associated with lower SIClamp in African Americans (β = -0.45, SE = 0.11, P < 0.001) but not Caucasian Americans (β = -0.42, SE = 0.30, P = 0.17). A peripheral fat distribution (leg fat adjusted for IAAT/SAAT) was associated with a higher SIClamp in African Americans (β = 0.11, SE = 0.05, P = 0.02) but lower SIClamp in Caucasian Americans (β = -0.28, SE = 0.14, P = 0.049). Lean mass was inversely associated with SIClamp in African Americans (β = -0.05, SE = 0.03, P = 0.04) but not Caucasian Americans (β = 0.08, SE = 0.05, P = 0.10) in the model for leg fat.

CONCLUSIONS

Measures of overall adiposity were more strongly associated with SIClamp in Caucasian Americans, whereas body fat distribution and lean mass showed stronger correlations with SIClamp in African Americans. Insulin sensitivity may have a genetic basis in African Americans that is reflected in the pattern of body fat distribution. These findings suggest a race-specific pathophysiology of insulin resistance, which has implications for the prevention of diabetes and related cardiometabolic diseases.

The Effects of Exercise and Physical Activity on Weight Loss and Maintenance

Obesity represents a major health problem in the United States and is associated with increased prevalence of cardiovascular (CV) disease risk factors. Physical activity (PA) and exercise training (ET) are associated with reduced CV risk, improved cardiometabolic risk factors, and facilitated weight loss through creating a negative energy balance. Clinicians need to counsel overweight and obese patients on how much PA/ET is needed to promote weight loss and weight loss maintenance. This will help establish realistic expectations and maximize improvements in CV risk factors. Although the minimum guidelines for aerobic PA (150 min of moderate or 75 min of vigorous physical activity per week) can improve CV health, these levels are generally inadequate for clinically significant weight loss or weight maintenance without caloric restriction. The purpose of this review is to evaluate the role of ET to promote clinically significant weight loss and promote weight maintenance. In particular, we will evaluate the likelihood of weight loss from ET programs composed of aerobic training only, resistance training only and programs that combine diet and ET. We will also explore the role of PA in promoting short-term and long-term weight maintenance.

Racial differences in weight loss, hemoglobin A1C, and blood lipid profiles after Roux-en-Y gastric bypass surgery

BACKGROUND

It is known that African American (AA) patients with obesity achieve less weight loss after Roux-en-Y gastric bypass surgery (RYGB) than their Caucasian (CA) counterparts. However, it is unclear how these differences in weight loss are reflected in clinical outcomes.

OBJECTIVES

To determine the effects of RYGB on hemoglobin A_1c (A_1c) and blood lipids in relationship to the variability in weight loss outcomes in a racially mixed patient population.

SETTING

University medical center.

METHODS

Retrospective analysis of clinical data from electronic medical records of CA, AA, and Hispanic American (HA) patients undergoing RYGB.

RESULTS

We used 2-way cluster analysis and identified 4 distinct weight loss×race clusters. CA patients separated into 2 clusters (45.5% and 28.2% weight loss, respectively), whereas, AA and HA patients separated into 1 cluster each (33.2% and 34.4% weight loss, respectively). Factors that significantly affected weight loss were race, age, gender, and physical activity as well as presence of hypertension and degenerative joint disease. Although all clusters had significant improvements in blood lipids, HA had an increase in total cholesterol (Total-c) and low-density lipoprotein cholesterol (LDL-c) at 2 years after surgery. All clusters had significant decreases in A_1c in the first year. At 2 years after RYGB, A_1c levels remained stable in CA and HA; however, AA had a significant increase. These racial differences in A_1c could not be explained by the smaller weight loss in AA patients.

CONCLUSION

Race is an important factor in the clinical outcomes of RYGB, especially in regard to diabetes control; however, its effect is not completely understood.

Abdominal adiposity change in white and black midlife women: The study of women's health across the nation

OBJECTIVE

The principal objective of this investigation was to compare the naturalistic intra-abdominal adipose tissue (IAAT) change among black and white women during midlife.

METHODS

A cohort of 222 (56%) white and 171 (44%) black midlife women were investigated in the Fat Patterning Study at the Chicago site of the Study of Women's Health Across the Nation. The subjects' total body fat was assessed by dual-energy X-ray absorptiometry and IAAT by a planimetric computed tomography (at the level of L4 -L5 ) annually over up to 4 years.

RESULTS

The total body fat at initial evaluation was higher in black women (45.1% ± 8.2%) when compared with white women (41.3% ± 8.7%, P < 0.001) and did not significantly change over the longitudinal follow-up. No significant racial differences were found in the mean annualized gain of IAAT (4.4% ± 0.5%) in models adjusted for total body fat, initial IAAT, age, race, time and race interaction, physical activity, depressive symptoms, menopausal status, and menopausal hormone therapy.

CONCLUSIONS

During a naturalistic observation, black and white midlife women had similar abdominal fat gain adjusted for differences in baseline adiposity. These data inform future research aimed to prevent IAAT gain during the critical midlife period of rising cardiovascular risk.

The Interplay Between Sex, Ethnicity, and Adipose Tissue Characteristics

The obesity epidemic in the USA affects disproportionately women and the ethnic minorities. On the other hand, female sex is traditionally associated with a favorable fat distribution preferentially in the subcutaneous depots of the lower body and with improved endocrine and metabolic function of the adipose tissue. However, these data are derived from predominantly non-Hispanic white populations. This review discusses fat distribution patterns in women of diverse ethnic backgrounds, together with data on the release of adipokines from adipose tissue in these populations. Very little information is available on how the metabolic function of the adipocyte differs depending on ethnicity. Thus, it becomes clear that future clinical and translational research should explicitly discuss and take into account the sex and ethnic background of the populations studied.

Impact of body composition during weight change on resting energy expenditure and homeostasis model assessment index in overweight nonsmoking adults

BACKGROUND

Weight change affects resting energy expenditure (REE) and metabolic risk factors. The impact of changes in individual body components on metabolism is unclear.

OBJECTIVE

We investigated changes in detailed body composition to assess their impacts on REE and insulin resistance.

DESIGN

Eighty-three healthy subjects [body mass index (BMI; in kg/m²) range: 20.2-46.8; 50% obese] were investigated at 2 occasions with weight changes between -11.2 and +6.5 kg (follow-up periods between 23.5 and 43.5 mo). Detailed body composition was measured by using the 4-component model and whole-body magnetic resonance imaging. REE, plasma thyroid hormone concentrations, and insulin resistance were measured by using standard methods.

RESULTS

Weight loss was associated with decreases in fat mass (FM) and fat-free mass (FFM) by 72.0% and 28.0%, respectively. A total of 87.9% of weight gain was attributed to FM. With weight loss, sizes of skeletal muscle, kidneys, heart, and all fat depots decreased. With weight gain, skeletal muscle, liver, kidney masses, and several adipose tissue depots increased except for visceral adipose tissue (VAT). After adjustments for FM and FFM, REE decreased with weight loss (by 0.22 MJ/d) and increased with weight gain (by 0.11 MJ/d). In a multiple stepwise regression analysis, changes in skeletal muscle, plasma triiodothyronine, and kidney masses explained 34.9%, 5.3%, and 4.5%, respectively, of the variance in changes in REE. A reduction in subcutaneous adipose tissue rather than VAT was associated with the improvement of insulin sensitivity with weight loss. Weight gain had no effect on insulin resistance.

CONCLUSION

Beyond a 2-compartment model, detailed changes in organ and tissue masses further add to explain changes in REE and insulin resistance.

Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women

Objective

Weight loss interventions have produced little change in insulin sensitivity in black women, but mean data may obscure metabolic benefit to some and adverse effects for others. Accordingly, we analyzed insulin sensitivity relative to fat mass change following a weight loss program.

Design and Methods

Fifty-four black women (BMI range 25.9 to 54.7 kg/m²) completed the 6-month program that included nutrition information and worksite exercise facilities. Fat mass was measured by dual-energy X-ray absorptiometry, and insulin sensitivity index (S_I) was calculated from an insulin-modified intravenous glucose tolerance test using the minimal model.

Results

Baseline S_I (range 0.74 to 7.58 l/mU⁻¹•min⁻¹) was inversely associated with fat mass (r = −0.516, p < 0.001), independent of age. On average, subjects lost fat mass (baseline 40.8 ± 12.4 to 39.4 ± 12.6 kg [mean ± SD], P < 0.01), but 17 women (32 %) actually gained fat mass. S_I for the group was unchanged (baseline 3.3 ± 1.7 to 3.2 ± 1.6, P = 0.67). However, the tertile with greatest fat mass loss (−3.6 kg, range −10.7 to −1.7 kg) improved insulin sensitivity (S_I +0.3 ± 1.2), whereas the tertile with net fat mass gain (+0.9 kg, range −0.1 to +3.8 kg) had reduced insulin sensitivity (S_I −0.7 ± 1.3) from baseline values (P < 0.05 by ANOVA).

Conclusions

Black women in a weight loss program who lose fat mass may have improved insulin sensitivity, but fat mass gain with diminished sensitivity is common. Additional support for participants who fail to achieve fat mass loss early in an intervention may be required for success.

Insulin sensitivity affects propensity to obesity in an ethnic-specific manner: results from two controlled weight loss intervention studies

Background

Risk for obesity differs with ethnicity/race and is associated with insulin sensitivity (S_I), insulin responsiveness, and dietary glycemic load (GL). The objective of this study was to test the hypotheses that, 1) obesity-prone, normal weight, African-American (AA) women would be more insulin sensitive than BMI-matched, never overweight AA women; 2) increased adiposity over time would be associated with greater baseline S_I and higher dietary GL in AA but not European-American (EA) women; and 3) increased adiposity over time would be predicted by S_I in women with high but not low acute insulin response to glucose (AIRg).

Methods

Two controlled weight loss interventions were conducted involving overweight (BMI 25.0-29.9 kg/m²) premenopausal AA and EA women. The first included matching with normal-weight (BMI <25.0 kg/m²) controls following weight loss, and then comparing S_I. The second included a 1-year follow-up of weight-reduced participants to identify predictors of change in %body fat. Main outcome measure in the first study was insulin sensitivity (S_I) as assessed with intravenous glucose tolerance test (IVGTT), and in the second study was change in %fat, as assessed with DXA, over one year. AIRg was assessed during IVGTT, and free-living diet was determined by food record.

Results

In the first study, formerly overweight AA women were 43% more insulin sensitive than BMI-matched never overweight AA (P < 0.05). In the second study, S_I was positively associated with change in %fat over 1 year only in AA women (P < 0.05) and women with high AIRg (P < 0.05). In addition, AA who were insulin sensitive and who consumed a higher GL diet tended to gain greater %fat (P = 0.086 for diet x S_I interaction). In both studies, AA women had higher AIRg (P < 0.001) than EA women.

Conclusions

Formerly overweight (obesity-prone) AA women were more insulin sensitive than never overweight AA women, a quality that may predispose to adiposity, particularly when combined with a high GL diet. This ethnicity/race-specific effect may be due to high insulin responsiveness among AA.

Elements of the metabolic syndrome: association with insulin sensitivity and effects of ethnicity

BACKGROUND

The objectives of the present study were, within a group of 322 healthy European American (EA) and African American (AA) women, to, (1) determine the extent to which insulin sensitivity (Si) was correlated with the elements of the metabolic syndrome using the third Adult Treatment Panel (ATP III) criteria; (2) determine if ethnicity affected the relationships between Si and the elements of the metabolic syndrome; and (3) determine the amount of variance in elements of the metabolic syndrome independently explained by fasting insulin, the acute insulin response to glucose (AIRg), and Si.

METHODS

Si and AIRg were assessed with a frequently-sampled intravenous glucose tolerance test and minimal modeling; total body fat with dual-energy x-ray absorptiometry; and intra-abdominal adipose tissue (IAAT) with computed tomography scanning.

RESULTS

Among all women combined, Si was associated with fasting glucose (r = -0.18, p < 0.01), waist circumference (r = -0.36, p < 0.001), and high-density lipoprotein cholesteraol (HDL-C; r = 0.18, p < 0.01). However, the association of Si with elements of the metabolic syndrome other than fasting glucose and waist circumference differed with ethnicity; among EA, Si was correlated with triglycerides (r = -0.28, p < 0.01) and HDL-C (r = 0.29, p < 0.001), whereas among AA, Si tended to be correlated with systolic blood pressure (r = -0.17, p = 0.059). In multiple regression modeling, fasting insulin was independently related to more elements of the metabolic syndrome (fasting glucose, waist circumference, triglycerides, systolic and diastolic blood pressure) than were Si or AIRg (both related only to fasting glucose), after adjusting for ethnicity, age, and total fat or IAAT.

CONCLUSIONS

Correlation of Si with elements of the metabolic syndrome differed with ethnic group. Fasting insulin, rather than Si, best predicted most elements of the metabolic syndrome.

Evolution of lipid profiles after bariatric surgery

BACKGROUND

The most commonly encountered dyslipidemia in obese individuals is characterized by a cluster of interrelated plasma lipid and lipoprotein abnormalities including hypertriglyceridemia, low HDL cholesterol values, and increased small, dense LDL cholesterol particles. The aim of this study was to assess the changes in lipid profiles at baseline (pre-operatively) and at follow-up (6, 12, and 18 months) after a laparoscopic Roux-en-Y gastric bypass (LRYGBP). A retrospective observational study was performed involving all patients who consecutively underwent a LRYGBP between January 1, 2007 and December 31, 2009. Fasting lipids sub-fractions (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) were measured and HOMA-IR calculated pre-operatively and at follow-up post-LRYGBP. Pearson's correlation coefficients were used to assess the relationship between excess weight loss (EWL) and lipid sub-fractions. ANOVA was used to assess the differences between each lipid sub-fraction at various time-points.

METHODS

One hundred twenty eight (N = 128) medical charts were reviewed, and those containing data on lipid fractions at the three follow-up time-points were analyzed. One hundred fourteen patients (N = 114), 84 of whom were women (73.7%), were finally included in the study.

RESULTS

Total cholesterol, LDL cholesterol, triglycerides, and HOMA-IR were significantly reduced after LRYGBP (P < 0.0005 for all). Inversely, HDL cholesterol disclosed a significant rise (P < 0.0005). Noteworthy significant associations between lipid subfractions and EWL were detected overall (P < 0.0005 for all). A gender effect was found since female patients displayed a milder association than male patients (P < 0.0005).

CONCLUSIONS

LRYGBP-induced weight loss improves the lipid profile while reducing insulin resistance, with male patients showing a better profile than female patients.

Effect of caloric intake on Western-style diet-induced intestinal tumors in a mouse model for hereditary colon cancer

Increased caloric intake has been associated with increased risk for cancer of the large intestine. We studied caloric intake effect on tumor formation in Apc1638( N/+ ) mice, a preclinical model for human familial adenomatous polyposis. Mice were fed a controlled AIN-76A diet or a new Western-style diet (NWD). Intestinal tumor development was evaluated after 6 mo of feeding 1) AIN-76A diet (fed ad libitum) vs. AIN-76A (caloric intake reduced 30%); 2) NWD (fed ad libitum) vs. NWD (caloric intake reduced 30%); and 3) AIN-76A (fed ad libitum) vs. NWD (paired-fed with NWD providing equal caloric intakes to AIN-76A). Intestinal tumor incidences were 78-100% with intergroup variation P > 0.05; however, tumor multiplicity responded differently to dietary treatment: 1) Tumor multiplicity was unchanged after AIN-76A (caloric intake reduced 30% vs. mice fed AIN-76A ad libitum); 2) tumor multiplicity was unchanged after NWD (caloric intake reduced 30% vs. NWD ad libitum); and 3) tumor multiplicity increased 130% after NWD was paired-fed with the same caloric intake as mice fed AIN-76A ad libitum (P < 0.05). Body weights showed no association with tumor development. Findings indicated modified nutrients in NWD were mainly responsible for increased tumors in mice fed NWD vs. AIN-76A in this preclinical mouse model for human FAP.

Aerobic exercise training conserves insulin sensitivity for 1 yr following weight loss in overweight women

The objectives of this study were to 1) identify the independent effects of exercise (aerobic or resistance training) and weight loss on whole body insulin sensitivity and 2) determine if aerobic or resistance training would be more successful for maintaining improved whole body insulin sensitivity 1 yr following weight loss. Subjects were 97 healthy, premenopausal women, body mass index (BMI) 27-30 kg/m(2). Following randomized assignment to one of three groups, diet only, diet + aerobic, or diet + resistance training until a BMI <25 kg/m(2) was achieved, body composition, fat distribution, and whole body insulin sensitivity were determined at baseline, in the weight reduced state, and at 1-yr follow up. The whole body insulin sensitivity index (S(I)) was determined using a frequently sampled intravenous glucose tolerance test. Results of repeated-measures ANOVA indicated a significant improvement in S(I) following weight loss. However, there were no group or group×time interactions. At 1-yr follow up, there were no significant time or group interactions for S(I;) however, there was a significant group×time interaction for S(I). Post hoc analysis revealed that women in the aerobic training group showed a significant increased S(I) from weight reduced to 1-yr follow up (P < 0.05), which was independent of intra-abdominal adipose tissue and %fat. No significant differences in S(I) from weight reduced to 1-yr follow up were observed for diet only or diet + resistance groups. Additionally, multiple linear regression analysis revealed that change in whole body insulin sensitivity from baseline to 1-yr follow up was independently associated with the change in Vo(2max) from baseline to 1-yr follow up (P < 0.05). These results suggest that long-term aerobic exercise training may conserve improvements in S(I) following weight loss and that maintaining cardiovascular fitness following weight loss may be important for maintaining improvements in S(I).

Intramyocellular lipid and insulin resistance: differential relationships in European and African Americans

Insulin resistance has been associated with the accumulation of fat within skeletal muscle fibers as intramyocellular lipid (IMCL). Here, we have examined in a cross-sectional study the interrelationships among IMCL, insulin sensitivity, and adiposity in European Americans (EAs) and African Americans (AAs). In 43 EA and 43 AA subjects, we measured soleus IMCL content with proton-magnetic resonance spectroscopy, insulin sensitivity with hyperinsulinemic-euglycemic clamp, and body composition with dual-energy X-ray absorptiometry. The AA and EA subgroups had similar IMCL content, insulin sensitivity, and percent fat, but only in EA was IMCL correlated with insulin sensitivity (r = -0.47, P < 0.01), BMI (r = 0.56, P < 0.01), percent fat (r = 0.35, P < 0.05), trunk fat (r = 0.47, P < 0.01), leg fat (r = 0.40, P < 0.05), and waist and hip circumferences (r = 0.54 and 0.55, respectively, P < 0.01). In a multiple regression model including IMCL, race, and a race by IMCL interaction, the interaction was found to be a significant predictor (t = 1.69, DF = 1, P = 0.0422). IMCL is related to insulin sensitivity and adiposity in EA but not in AA, suggesting that IMCL may not function as a pathophysiological factor in individuals of African descent. These results highlight ethnic differences in the determinants of insulin sensitivity and in the pathogenesis of the metabolic syndrome trait cluster.

Respiratory quotient predicts fat mass gain in premenopausal women

High respiratory quotient (RQ) has been associated with fat mass (FM) gain in some, but not all studies. Variability among results may reflect differences in the RQ variable measured (fasting vs. 24-h) or may be due to differences in control for factors that affect RQ, such as diet, energy balance, circulating insulin, and insulin sensitivity. The objective of this study was to determine whether different RQ values (fasting, sleeping, nonsleeping, and 24-h) would predict change in FM over 2 years in obesity-prone women, controlling for diet and adjusting for energy balance, circulating insulin, and insulin sensitivity. Participants were 33 previously overweight premenopausal women. Fasting, sleeping, nonsleeping, and 24-h RQ values were measured during controlled-diet conditions by respiratory chamber calorimetry. Intravenous glucose tolerance tests were also performed to adjust for fasting insulin, acute insulin response to glucose, and insulin sensitivity. Over the following 2 years, changes in FM were tracked annually by dual energy X-ray absorptiometry. High nonsleeping RQ (NSRQ) predicted 2-year change in FM independently of energy balance, circulating insulin, and insulin sensitivity. This observation suggests that low postprandial fat oxidation may uniquely predispose obesity-prone individuals to accrual of adipose tissue.

Dietary calcium intake is associated with less gain in intra-abdominal adipose tissue over 1 year

Calcium intake is reported to enhance weight loss with a preferential loss in trunk fat. Discrepant findings exist as to the effects of calcium intake on longitudinal changes in total fat mass and central fat deposition. Therefore, the purpose of this study was to determine associations between dietary calcium intake and 1-year change in body composition and fat distribution, specifically intra-abdominal adipose tissue (IAAT). A total of 119 healthy, premenopausal women were evaluated at baseline and 1 year later. Average dietary calcium was determined via 4-day food records. Total fat was determined by dual-energy X-ray absorptiometry (DXA) and subcutaneous abdominal adipose tissue (SAAT) and IAAT by computed tomography. Over the study period, participants' reported daily calcium and energy intakes were 610.0 ± 229.9 mg and 1,623.1 ± 348.5 kcal, respectively. The mean change in weight, total fat, IAAT, and SAAT was 4.9 ± 4.4 kg, 5.3 ± 4.0 kg, 7.7 ± 19.5 cm(2), and 49.3 ± 81.1 cm(2), respectively. Average calcium intake was significantly, inversely associated with 1-year change in IAAT (standardized β: -0.23, P < 0.05) after adjusting for confounding variables. For every 100 mg/day of calcium consumed, gain in IAAT was reduced by 2.7 cm(2). No significant associations were observed for average calcium intake with change in weight, total fat, or SAAT. In conclusion, dietary calcium intake was significantly associated with less gain in IAAT over 1 year in premenopausal women. Further investigation is needed to verify these findings and determine the calcium intake needed to exert beneficial effects on fat distribution.

Imaging body composition in obesity and weight loss: challenges and opportunities

Obesity is a threat to public health worldwide primarily due to the comorbidities related to visceral adiposity, inflammation, and insulin resistance that increase risk for type 2 diabetes and cardiovascular disease. The translational research portfolio that originally described these risk factors was significantly enhanced by imaging techniques, such as dual-energy X-ray absorptiometry (DEXA), computed tomography (CT), and magnetic resonance imaging (MRI). In this article, we briefly review the important contributions of these techniques to understand the role of body composition in the pathogenesis of obesity-related complications. Notably, these imaging techniques have contributed greatly to recent findings identifying gender and racial differences in body composition and patterns of body composition change during weight loss. Although these techniques have the ability to generate good-quality body composition data, each possesses limitations. For example, DEXA is unable to differentiate type of fat, CT has better resolution but provides greater ionizing radiation exposure, and MRI tends to require longer imaging times and specialized equipment for acquisition and analysis. With the serious need for efficacious and cost-effective therapies to appropriately identify and treat at-risk obese individuals, there is greater need for translational tools that can further elucidate the interplay between body composition and the metabolic aberrations associated with obesity. In conclusion, we will offer our perspective on the evolution toward an ideal imaging method for body composition assessment in obesity and weight loss, and the challenges remaining to achieve this goal.

Glucose metabolism and diet predict changes in adiposity and fat distribution in weight-reduced women

Among obesity-prone individuals, metabolic state may interact with diet in determining body composition. We tested the hypotheses that, among 103 weight-reduced women over 1 year, (i) insulin sensitivity would be positively associated with change in %fat; (ii) this association would be modulated by dietary glycemic load (GL); and (iii) changes in fat distribution would be related to indexes of glucose metabolism. Insulin sensitivity, glucose effectiveness, fasting and postchallenge insulin and glucose, and glucose tolerance were assessed during intravenous glucose tolerance test (IVGTT). Changes in %fat and fat distribution were examined using dual-energy X-ray absorptiometry and computed tomography. Dietary GL was assessed on 67 women using food records. On average, women showed a +5.3 +/- 3.0% change in %fat over 1 year, with the magnitude of this change being greater in relatively insulin sensitive women (+6.0 +/- 0.4%, mean +/- s.e.m.) than in relatively insulin resistant women (+4.4 +/- 0.4 kg; P < 0.05). Women who were relatively insulin sensitive and who consumed a higher GL diet showed a +6.8 +/- 0.7% change in %fat, which was greater than those who were less insulin sensitive, regardless of diet (P < 0.05), but did not differ from women who were relatively insulin sensitive and who consumed a lower GL diet (P = 0.105). Changes in intra-abdominal and deep subcutaneous abdominal fat were inversely associated with the postchallenge decline in serum glucose. In conclusion, greater insulin sensitivity may predispose to adiposity among weight reduced women, an effect that may be ameliorated by a lower GL diet. The potential association between indexes of glucose disposal and changes in fat distribution warrants further study.

The neurohormonal regulation of energy intake in relation to bariatric surgery for obesity

Obesity has reached pandemic proportions, with bariatric surgery representing the only currently available treatment demonstrating long-term effectiveness. Over 200,000 bariatric procedures are performed each year in the US alone. Given the reliable and singular success of bariatric procedures, increased attention is being paid to identifying the accompanying neurohormonal changes that may contribute to the resulting decrease in energy intake. Numerous investigations of postsurgical changes in gut peptides have been conducted, suggesting greater alterations in endocrine function in combination restrictive and malabsorptive procedures (e.g., Roux-en-Y gastric bypass) as compared to purely restrictive procedures (e.g., gastric banding), which may contribute to the increased effectiveness of combination procedures. However, very few studies have been performed and relatively little is known about changes in neural activation that may result from bariatric procedures, which likely interact with changes in gut peptides to influence postsurgical caloric intake. This review provides a background in the neurohormonal regulation of energy intake and discusses how differing forms of bariatric surgery may affect the neurohormonal network, with emphasis on Roux-en-Y gastric bypass, the most commonly performed procedure worldwide. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.

Vitamin D intake is associated with insulin sensitivity in African American, but not European American, women

Background

The prevalence of type 2 diabetes is higher among African Americans (AA) vs European Americans (EA), independent of obesity and other known confounders. Although the reason for this disparity is not known, it is possible that relatively low levels of vitamin D among AA may contribute, as vitamin D has been positively associated with insulin sensitivity in some studies. The objective of this study was to test the hypothesis that dietary vitamin D would be associated with a robust measure of insulin sensitivity in AA and EA women.

Methods

Subjects were 115 African American (AA) and 137 European American (EA) healthy, premenopausal women. Dietary intake was determined with 4-day food records; the insulin sensitivity index (S_I) with a frequently-sampled intravenous glucose tolerance test and minimal modeling; the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) with fasting insulin and glucose; and body composition with dual-energy X-ray absorptiometry.

Results

Vitamin D intake was positively associated with S_I (standardized β = 0.18, P = 0.05) and inversely associated with HOMA-IR (standardized β = -0.26, P = 0.007) in AA, and the relationships were independent of age, total body fat, energy intake, and % kcal from fat. Vitamin D intake was not significantly associated with indices of insulin sensitivity/resistance in EA (standardized β = 0.03, P = 0.74 and standardized β = 0.02, P = 0.85 for S_I and HOMA-IR, respectively). Similar to vitamin D, dietary calcium was associated with S_I and HOMA-IR among AA but not EA.

Conclusions

This study provides novel findings that dietary vitamin D and calcium were independently associated with insulin sensitivity in AA, but not EA. Promotion of these nutrients in the diet may reduce health disparities in type 2 diabetes risk among AA, although longitudinal and intervention studies are required.

Diet-induced changes in intra-abdominal adipose tissue and CVD risk in American women

The aim of the study was to determine what effect weight loss had on intra-abdominal adipose tissue (IAAT) and cardiovascular disease (CVD) risk in 135 premenopausal overweight African-American (AA) and European-American (EA) women matched for BMI. Blood lipids, systolic blood pressure (SBP), diastolic BP (DBP), and IAAT (computed tomography determined) were examined prior to and after an 800 kcal/day diet producing 12 kg-weight loss. Significant decreases in IAAT (approximately 38%), total cholesterol (TC; 3%), low-density lipoproteins (LDLs: 6%), triglycerides (TGs: 27%), cholesterol/high-density lipoprotein ratio (C/HDL ratio: 18%), SBP (3%), and DBP (3%) occurred while HDL increased (16%), following weight loss and 1 month energy balance. Significant interactions between time and race showed that AA women decreased TG and increased HDL proportionately less than EA women. After adjusting for Delta IAAT, none of the CVD variables significantly changed after weight loss with the exception of HDL and C/HDL ratio. After adjusting for Delta LF (leg fat), Delta TC, Delta TG, Delta LDL, and Delta C/HDL ratio were significantly different. Multiple regression showed that independent of each other, Delta IAAT was significantly and positively related to Delta TC (adjusted beta = 0.24) and Delta TG (adjusted beta = 0.47), and Delta LF was negatively related to Delta TC (adjusted beta = -0.19) and Delta TG (adjusted beta = -0.18). Overweight and premenopausal AA and EA women benefitted from weight loss by decreasing IAAT and improving CVD risk. The changes in IAAT were significantly related to blood lipids, but loss of LF seems to be related to reduced improvement in TC and TG. Based on these results, interventions should focus on changes on IAAT.

Cardiometabolic risk among African American women: a pilot study

OBJECTIVE

This study aimed to determine the associations of the Homeostatic Model of Assessment-insulin resistance (HOMA-ir), acanthosis nigricans, high-sensitivity C-reactive protein (hs-CRP), and plasminogen activator inhibitor-1 (PAI-1) with 2 of the commonly used definitions of metabolic syndrome (Adult Treatment Panel III [ATP III] and International Diabetes Federation [IDF]) among reproductive-age, healthy, free-living African American women.

METHODS

A pilot study with a cross-sectional design examined 33 African American women aged 20 to 46 years (mean [SD], 31.24 [7.25] years) for the presence of metabolic syndrome determined by ATP III and IDF criteria, insulin resistance (HOMA-ir and/or acanthosis nigricans), degree of inflammation (hs-CRP), and presence of dysfibrinolysis (PAI-1).

RESULTS

HOMA-ir identified insulin resistance in 27 (81.8%) women, whereas the presence of acanthosis nigricans indicated that 16 (48%) of these women manifested insulin resistance. Metabolic syndrome was found in 7 women (21.2%) by ATP III or in 9 (27.3%) women by IDF criteria. Bivariate correlations showed associations between HOMA-ir and waist circumference, body mass index (BMI), acanthosis nigricans, and the ATP III and IDF definitions for metabolic syndrome. Plasminogen activator inhibitor-1 was significantly correlated with waist circumference, BMI, fasting glucose, HOMA-ir, and ATP III. Both HOMA-ir and PAI-1 were significantly and negatively correlated with high-density lipoprotein cholesterol. High-sensitivity CRP was significantly correlated with BMI and 2-hour postglucose.

CONCLUSION

Both dysfibrinolysis (PAI-1 levels) and insulin resistance (HOMA-ir), when individually regressed on the ATP III definition of metabolic syndrome, explained 32% and 29% of the respective variance. The addition of HOMA-ir measurement may significantly improve early recognition of cardiometabolic risk among reproductive-age African American women who have not yet met the criteria for the ATP III or IDF definitions of metabolic syndrome. Likewise, acanthosis nigricans is potentially a clinically significant screening tool when used to determine early recognition of insulin resistance and/or cardiometabolic risk among this population. African American women's risk for cardiovascular disease is likely underestimated based on the sole use of ATP III criteria for diagnosis of metabolic syndrome. Clinicians should consider a broader definition of risk than that contained within ATP III. Inclusion of biomarkers of inflammation and dysfibrinolysis, along with measures of insulin resistance, may add to early detection of cardiometabolic risk and ultimate reduction in cardiovascular health disparities among African American women.

Rosiglitazone is more effective than metformin in improving fasting indexes of glucose metabolism in severely obese, non-diabetic patients

AIM

In obese patients, the diet-induced weight loss markedly improves glucose tolerance with an increase in insulin sensitivity and a partial reduction of insulin secretion. The association with metformin treatment might potentiate the effect of diet alone.

METHODS

From patients admitted to our Nutritional Division for diet programme, we selected obese, non-diabetic, uncomplicated patients with age 18-65 years and body mass index 35-50 kg/m(2) and studied the effects of a 6-month pharmacological treatment with either metformin (850 mg twice daily) or rosiglitazone (4 mg twice daily) on possible changes in body weight, fat mass, glucose and lipids metabolism.

RESULTS

A significant weight loss and reduction of fat mass was demonstrated with metformin (-9.7 +/- 1.8 kg and -6.6 +/- 1.1 kg) and also with rosiglitazone (-11.0 +/- 1.9 kg and -7.2 +/- 1.8 kg), without fluid retention in either treatment group. Rosiglitazone administration induced a significant decrease in glucose concentration (4.7 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, p < 0.005) and insulin-circulating level (13.6 +/- 1.5 vs. 8.0 +/- 0.,7 microU/ml, p < 0.005), an increase in insulin sensitivity as measured by homeostatic model assessment (HOMA) of insulin sensitivity (68.9 +/- 8.8 vs. 109.9 +/- 10.3, p < 0.005) with a concomitant decrease in beta-cell function as measured by HOMA of beta-cell function (163.2 +/- 16.1 vs. 127.4 +/- 8.4, p < 0.005). In contrast, metformin did not produce any significant effect on blood glucose concentration, insulin level and HOMA2 indexes. No adverse events were registered with pharmacological treatments.

CONCLUSION

Our study shows that in severely obese, non-diabetic, hyperinsulinaemic patients undergoing a nutritional programme, rosiglitazone is more effective than metformin in producing favourable changes in fasting-based indexes of glucose metabolism, with a reduction of both insulin resistance and hyperinsulinaemia. In spite of previous studies reporting rosiglitazone-induced body weight gain, in our study the joint treatment with diet and rosiglitazone was accompanied by weight loss and fat mass reduction.

Moderate protein intake improves total and regional body composition and insulin sensitivity in overweight adults

A high protein intake (approximately 40% of energy intake) combined with aerobic and resistance exercise training is more closely associated with improved body composition and cardiovascular risk profile than a traditional protein intake (approximately 15% of intake) combined with moderate-intensity aerobic exercise. However, there is concern that such high-protein diets may adversely affect health. We therefore tested the hypothesis that moderate protein intake (approximately 25% of energy intake) would elicit similar benefits on body composition and metabolic profile as high protein intake. Twenty-four overweight/obese men and women (body mass index [BMI] = 32.2 +/- 3.4, percentage of body fat [%BF] = 37.3 +/- 8.0) were matched for BMI and %BF and randomly assigned to one of 3 groups for a 3-month nutrition/exercise training intervention: (1) high-protein diet (approximately 40% of energy intake) and combined high-intensity resistance and cardiovascular training (HPEx, n = 8, 5 female and 3 male), (2) moderate-protein diet (approximately 25% of energy intake) and combined high-intensity resistance and cardiovascular training (MPEx, n = 8, 5 female and 3 male), or (3) high-protein diet only (HPNx, n = 8, 5 female and 3 male). Total and regional body composition (dual-energy x-ray absorptiometry), insulin sensitivity (insulin sensitivity index to the oral glucose tolerance test), insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), IGF binding protein-3 (IGFBP-3), and blood lipids were measured at baseline and after the intervention. All groups experienced significant (P < .05) and similar losses of body weight, BMI, and total and abdominal %BF, and similar improvements in insulin sensitivity (HPEx, 6.3 +/- 1.2 vs 9.5 +/- 0.98; MPEx, 6.2 +/- 1.4 vs 8.4 +/- 1.6; HPNx, 3.7 +/- 1.1 vs 7.0 +/- 1.1; insulin sensitivity index to the oral glucose tolerance test; P < .05) and leptin levels. Furthermore, the HPEx group demonstrated decreases in total cholesterol (TC) and triglycerides, and increases in IGF-1 and IGFBP-1. The MPEx group experienced decreases in TC, whereas the HPNx group had increases in high-density lipoprotein cholesterol, TC to high-density lipoprotein, IGF-1, and IGFBP-1. In conclusion, moderate protein intake elicits similar benefits in body composition and insulin sensitivity as a high-protein diet. These findings may have practical implications for individuals interested in diets containing elevated dietary protein.

Allometric relationship between changes of visceral fat and total fat mass

OBJECTIVE

To elucidate the mathematical relationship between changes of visceral adipose tissue (VAT) and total body fat mass (FM) during weight loss.

DESIGN

We hypothesized that changes of VAT mass are allometrically related to changes of FM, regardless of the type of weight-loss intervention, as defined by the differential equation dVAT/dFM=k x VAT/FM, where k is a dimensionless constant. We performed a systematic search of the published literature for studies that included measurements of VAT changes via magnetic resonance imaging (MRI) or computed tomography (CT) imaging along with measurements of FM changes by dual-energy X-ray absorptiometry, hydrodensitometry, air-displacement plethysmography or whole-body MRI or CT imaging. We then examined whether or not the data could be explained by the allometric model.

RESULT

We found 37 published studies satisfying our search criteria, representing 1407 men and women of various ethnicities, degrees of adiposity and weight-loss interventions. The hypothesized allometric equation relating changes of VAT and FM accurately modeled the data for both men and women and for all methods of weight loss studied. The best-fit value for the dimensionless constant was k=1.3+/-0.1 and the resulting model had an R(2)=0.73.

CONCLUSION

This is the first report to reveal an allometric relationship between changes of VAT and FM that holds for both genders as well as a wide variety of weight-loss interventions including bariatric surgery, caloric restriction with or without exercise and exercise alone. We conclude that changes of VAT are primarily determined by FM changes as well as the initial VAT to FM ratio.

IAAT, catecholamines, and parity in African-American and European-American women

OBJECTIVE

We have recently reported that parous European-American (EA) women have disproportionately more intra-abdominal adipose tissue (IAAT) than their nulliparous counterparts. Mediating mechanisms for IAAT accumulation remain unknown; however, some evidence suggests a possible catecholamine link. The objective of this study was to determine whether the IAAT-parity relationship found in EA women exists in African-American (AA) women and to determine whether catecholamines play a mediating role.

METHODS AND PROCEDURES

Subjects included 44 EA and 47 AA premenopausal women. Free-living physical activity by doubly labeled water (activity-related time equivalent (ARTE)), body composition (air plethysmography, computed tomography), and 24-h fractionated urinary catecholamines were measured.

RESULTS

Repeated measures ANOVA revealed parous EA and AA women had significantly higher IAAT than their nulliparous counterparts (100.1 +/- 28.5 and 76.2 +/- 34.8 cm(2) vs. 75.9 +/- 29.1 and 59.6 +/- 15.0 cm(2)). In AA women and nulliparous women, 24-h urinary dopamine was significantly higher (AA parous 260.8 +/- 88; EA parous 197.2 +/- 78.8; AA nulliparous 376.5 +/- 81; EA nulliparous 289.6 +/- 62). Multiple regression analysis for modeling IAAT indicated that race, parity, dopamine, ARTE, and VO(2max) were all significant and independent contributors to the model (Unstandardized betas: race -32.6 +/- 7.4; parity (number of births) 10.0 +/- 3.4; 24-h urinary dopamine 0.08 +/- 0.04; ARTE (min/day) -0.09 +/- 0.04; VO(2max) (ml/kg/min) -2.8 +/- 1.0).

DISCUSSION

Independent of the potential confounders: age, race, percent body fat, IAAT, 24-h fractionated urinary catecholamines, physical activity, and VO(2max), parous EA and AA women had more IAAT than their nulliparous counterparts. Of the catecholamines, dopamine was found to be significantly lower in parous women and higher in AA's. Dopamine, however, did not explain racial or parity differences in IAAT.

Factors associated with percent change in visceral versus subcutaneous abdominal fat during weight loss: findings from a systematic review

BACKGROUND

Visceral adipose tissue (VAT) is associated with greater obesity-related metabolic disturbance. Many studies have reported preferential loss of VAT with weight loss.

OBJECTIVE

This systematic review looks for factors associated with preferential loss of VAT relative to subcutaneous abdominal fat (SAT) during weight loss.

DESIGN

Medline and Embase were searched for imaging-based measurements of VAT and subcutaneous abdominal adipose tissue (SAT) before and after weight loss interventions. We examine for factors that influences the percentage change in VAT versus SAT (%deltaV/%deltaS) with weight loss. Linear regression analyses were performed on the complete data set and on subgroups of studies. Factors examined included percentage weight loss, degree of caloric restriction, exercise, initial body mass index (BMI), gender, time of follow-up and baseline VAT/SAT.

RESULTS

There were 61 studies with a total of 98 cohort time points extracted. Percentage weight loss was the only variable that influenced %deltaV/%deltaS (r=-0.29, P=0.005). Modest weight loss generated preferential loss of VAT, but with greater weight loss this effect was attenuated. The method of weight loss was not an influence with one exception. Very-low-calorie diets (VLCDs) provided exceptional short-term (<4 weeks) preferential VAT loss. But this effect was lost by 12-14 weeks.

CONCLUSIONS

Visceral adipose tissue is lost preferentially with modest weight loss, but the effect is attenuated with greater weight loss. Acute caloric restriction, using VLCD, produces early preferential loss of VAT. These observations may help to explain the metabolic benefits of modest weight loss.

Lifestyle intervention in individuals with normal versus impaired glucose tolerance

BACKGROUND

Lifestyle intervention is effective in the prevention of type 2 diabetes in individuals with impaired glucose tolerance (IGT). It is currently unknown whether it has beneficial effects on metabolism to a similar extent, in individuals with normal glucose tolerance (NGT) compared to individuals with IGT.

MATERIALS AND METHODS

Data from 181 subjects (133 with NGT and at risk for type 2 diabetes and 48 with IGT) who participated in the Tuebingen Lifestyle Intervention Program with increase in physical activity and decrease in caloric intake were included into this study. Body fat distribution was quantified by whole-body magnetic resonance (MR) tomography and liver fat and intramyocellular fat by (1)H-MR spectroscopy. Insulin sensitivity was estimated from an oral glucose tolerance test (OGTT).

RESULTS

After 9 +/- 2 months of follow-up, the diagnosis of IGT was reversed in 24 out of 48 individuals. Only 14 out of 133 participants with NGT developed IGT. Body weight decreased in both groups by 3% (both P < 0.0001). Two-hour glucose concentrations during an OGTT decreased in individuals with IGT (-14%, P < 0.0001) but not with NGT (+2%, P = 0.66). Insulin sensitivity increased both in individuals with IGT (+9%, P = 0.04) and NGT (+17%, P < 0.0001). Visceral fat (-8%, P = 0.006), liver fat (-28%, P < 0.0001) and intramyocellular fat (-15%, P = 0.006) decreased in participants with IGT. In participants with NGT these changes were significant for visceral fat (-16%, P < 0.0001) and liver fat (-35%, P < 0.0001).

CONCLUSIONS

Moderate weight loss under a lifestyle intervention with reduction in total, visceral and ectopic fat and increase in insulin sensitivity improves glucose tolerance in individuals with IGT but not with NGT. In individuals with NGT, the beneficial effects of a lifestyle intervention on fat distribution and insulin sensitivity possibly prevent future deterioration in glucose tolerance.

Cancer progression in the transgenic adenocarcinoma of mouse prostate mouse is related to energy balance, body mass, and body composition, but not food intake

Calorie restriction can inhibit or delay carcinogenesis, reportedly due to a reduction in calorie intake rather than by concurrent changes in body mass and/or composition. Our objective was to test the hypothesis that body mass and/or composition have an important effect, independent of energy intake, on the benefits or hazards associated with calorie restriction or overeating, respectively. In the first experiment, transgenic mice that spontaneously develop prostate cancer [transgenic adenocarcinoma of mouse prostate (TRAMP)] were housed at 27 degrees C or 22 degrees C and pair fed the same diet for 21 weeks (95% of ad libitum intake at 27 degrees C). In the second experiment, TRAMP mice were housed at 27 degrees C or 22 degrees C and fed the same diet ad libitum for 21 weeks. Despite a similar calorie intake, pair-fed mice at 27 degrees C (PF27) were heavier (28.3 +/- 3.3 versus 17.6 +/- 1.6 g at 21 weeks; P < 0.001; mean +/- SD) and had greater fat (6.4 +/- 2.1 versus 1.9 +/- 0.3 g; P < 0.001) and lean mass (P < 0.001) than pair-fed mice at 22 degrees C. Furthermore, PF27 mice had greater levels of serum leptin (P < 0.001), lower levels of adiponectin (P < 0.05), and a greater frequency of prostatic adenocarcinoma (P < 0.05). In contrast, ad libitum-fed mice housed at 22 degrees C consumed approximately 30% more calories than ad libitum-fed mice at 27 degrees C, but there was no difference between groups in body composition or cancer progression. These results imply that the ability of calorie restriction to inhibit or delay cancer incidence and progression is mediated in part by changes in energy balance, body mass, and/or body composition rather than calorie intake per se, suggesting that excess calorie retention, rather than consumption, confers cancer risk.

Changes in fat-free mass during significant weight loss: a systematic review

OBJECTIVE

To identify the proportion of weight lost as fat-free mass (FFM) by various weight loss interventions.

METHODS

Medline and Embase were systematically searched for reliable measurements of FFM before and after weight loss of >10 kg and eligible data were pooled. In a fixed effect model of % FFM loss/weight loss (%FFML), linear regression analysis was used to determine the influence of degree of caloric restriction, exercise, magnitude of weight loss, initial body mass index (BMI) and type of surgery.

RESULTS

Data were included from 26 cohorts treated with dietary and behavioral interventions and 29 cohorts of bariatric surgery patients. The degree of caloric restriction was positively associated with %FFML (r (2)=0.31, P=0.006) and in three randomized controlled trials exercise was shown to decrease %FFML. Compared with laparoscopic adjustable gastric banding (LAGB), biliopancreatic diversion (BPD) and roux en Y gastric bypass (RYGB) caused greater log(e) (natural log) %FFML (r (2)=0.453, P<0.001). Differences in log(e) %FFML between surgical procedures were independent of initial BMI and magnitude of weight loss.

CONCLUSIONS

The degree of caloric restriction, exercise and rate of weight loss influence the proportion of weight lost as FFM after non-surgical interventions. For surgical interventions, BPD and RYGB result in greater %FFML than LAGB.

Relationship between insulin sensitivity and in vivo mitochondrial function in skeletal muscle

Recent data have shown that individuals with low insulin sensitivity (S(I)) also have reduced whole body maximal oxygen uptake. The objectives of this study were to determine 1) whether muscle mitochondrial function was independently related to S(I) after being adjusted for known determinants of S(I) and 2) whether lower S(I) among African-American (AA) vs. Caucasian-American (CA) women was due to lower muscle mitochondrial function among AA women. Subjects were 37 CA and 22 AA premenopausal women (age: 33.6 +/- 6.3 yr). Mitochondrial function [time constant of ADP (ADP(tc))] was assessed during a 90-s unilateral isometric contraction using (31)P magnetic resonance spectroscopy, S(I) with an intravenous glucose tolerance test, body composition by dual-energy X-ray absorptiometry, and visceral adipose tissue (VAT) with computed tomography. ANOVA was used to compare AA and CA groups, and multiple linear regression modeling was used to identify independent predictors of S(I). Between-race comparisons indicated that muscle oxidative capacity was lower among AAs vs. CAs (ADP(tc): 25.6 +/- 9.8 vs. 21.4 +/- 9.9 s). Multiple linear regression models for the dependent variable S(I) contained 1) VAT and race and 2) VAT, race, and ADP(tc). Significant independent effects for all predictor variables were observed in both the first (r(2) = 0.345) and second (r(2) = 0.410) models. The partial correlation for race was lower in the second model (-0.404 vs. -0.300), suggesting that muscle mitochondrial function contributed to the racial difference in S(I). Lower muscle mitochondrial function among AAs may in part explain lower S(I) among them.

Correlations between measures of insulin sensitivity and weight loss

OBJECTIVE

Many formulas have been proposed to calculate insulin sensitivity and studies have shown their effectiveness. However, few studies have been done to compare formulas.

METHODS

Seventy-two obese participants completed a randomized weight loss study. Weight loss, change in body fat and change in waist circumference were used as surrogates for change in insulin sensitivity. Correlation coefficients were calculated for each of these surrogates with proposed formulas for insulin sensitivity found in the literature.

RESULTS

The change in insulin sensitivity using the formula proposed by McAuley (exp(2.63-0.28 x ln(fasting insulin)-0.31 x ln(fasting triglyceride in mmol/l)) showed the greatest correlation with weight loss (r=-0.59, p<0.0001) and was statistically superior to change in fasting glucose, fasting insulin and homeostasis model assessment (HOMA).

CONCLUSIONS

The insulin sensitivity formula proposed by McAuley provides an accurate means of detecting insulin resistance. As it does not require a glucose tolerance test, it is also easier and less expensive than most other formulas. Use of this formula rather than fasting glucose would detect many more patients with insulin resistance who are at risk for subsequent diabetes and other complications.

Role of diet in the treatment of polycystic ovary syndrome

OBJECTIVE

To determine whether eucaloric diets either enriched with monounsaturated fatty acids (MUFA; 17% energy) or low in carbohydrates (Low CHO; 43% energy) would increase insulin sensitivity (Si) and decrease circulating insulin concentrations, relative to a standard diet (STD; 56% CHO, 31% fat, 16% protein), among women with polycystic ovary syndrome (PCOS).

DESIGN

Crossover.

SETTING

Academic research environment.

PATIENT(S)

Healthy women with PCOS not on hormonal or insulin-sensitizing therapy.

INTERVENTION(S)

Subjects consumed three, 16-day, eucaloric diets, each separated by a 3-week washout period. A frequently sampled, intravenous, glucose tolerance test was administered at baseline and following each diet.

MAIN OUTCOME MEASURE(S)

Fasting glucose, insulin, the acute insulin response to glucose (AIRg), Si, sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), total testosterone (T), free T, A4, total cholesterol, high-density lipoprotein cholesterol (HDL-C), tryglycerides (TG), and free fatty acids (FFA).

RESULT(S)

Fasting insulin was lower following the Low CHO diet relative to the STD diet; AIRg was lower following the Low CHO diet relative to the MUFA diet. Fasting glucose, Si, and the circulating concentrations of reproductive hormones were not significantly affected by the intervention.

CONCLUSION(S)

A moderate reduction in dietary carbohydrate reduced the fasting and postchallenge insulin concentrations among women with PCOS, which, over time, may improve reproductive/endocrine outcomes.

Independent association of insulin resistance with larger amounts of intermuscular adipose tissue and a greater acute insulin response to glucose in African American than in white nondiabetic women

BACKGROUND

African Americans (AAs) have a higher prevalence of obesity and type 2 diabetes than do whites. Higher insulin resistance and hyperinsulinemia have been reported in adult AAs than in whites. Differences in adipose tissue and its distribution may account for these findings.

OBJECTIVE

The objective was to ascertain whether differences between AA and white women in adipose tissue (AT) and skeletal muscle (SM) volumes account for ethnic differences in insulin resistance.

DESIGN

We used whole-body magnetic resonance imaging to measure AT and SM volumes and used the intravenous-glucose-tolerance test to measure insulin resistance.

RESULTS

AAs (n = 32) were 29-42% more insulin resistant than were whites (n = 28) after adjustment for weight and height or any AT volumes (P < 0.05). After adjustment for SM volume, the difference decreased to 19% and became nonsignificant. AAs had a 163% greater acute insulin response to glucose than did whites; this difference was significant even after adjustment for insulin sensivitity index, weight, height, and any magnetic resonance imaging measures. With respect to regional AT volumes, an association independent of race, weight, height, and SM volume was found only between increased intermuscular AT and lower insulin sensitivity index.

CONCLUSIONS

Premenopausal AA women had significantly higher insulin resistance and acute insulin response to glucose than did their white counterparts. Whereas the difference in insulin resistance was partially accounted for by a greater SM volume in the AAs than in the whites, the difference in the acute insulin response to glucose was independent of any AT and SM measures and was disproportionately larger than expected according to the difference in insulin resistance. In addition, whole-body intermuscular AT was an important independent correlate of insulin resistance.

African American Women, Metabolic Syndrome, and National Cholesterol Education Program Criteria

BACKGROUND

The association between elevated levels of triglycerides and insulin may be weaker in African American women (AAW) than in women of other groups, leading to under diagnosis of the metabolic syndrome (MetS) in AAW when using the National Cholesterol Education Program (NCEP) criteria, as those criteria do not include a marker of insulin resistance, using elevated triglycerides to provide an indirect indication of insulin resistance.

OBJECTIVES

To determine the degree of agreement between two definitions for the MetS, that described by the NCEP and the NCEP criteria with the addition of a marker of insulin resistance in a sample of AAW.

METHOD

This non experimental pilot study took place in the General Clinical Research Center of a major medical center. Thirty-three AAW 19-45 years of age were screened using the NCEP criteria for MetS, additional markers of insulin resistance, and a 2-hour Oral Glucose Tolerance Test.

FINDINGS

Six (18%) women were classified as having the MetS using the NCEP criteria. When one of three markers for insulin resistance (hyperinsulinemia, acanthosis nigricans, or Homeostatic Model Assessment Insulin Resistance) was added to the criteria, 15 (45.5%) to 19 (59.5%) of the women were then identified as having MetS.

DISCUSSION

As identified in the literature, the prevalence of cardiovascular disease risk in AAW may be underestimated based on the sole use of the NCEP criteria. Further, because there is some evidence that insulin resistance develops before many other indicators, the addition of a marker of insulin resistance may assist in earlier identification of AAW at high risk for cardiovascular disease.

Analysis of weight loss outcomes using VLCD in black and white overweight and obese women with and without metabolic syndrome

OBJECTIVE

To evaluate the efficacy of very low calorie diet (VLCD) in black and white obese women. Changes in weight, metabolic profile, and body composition are assessed.

METHOD

Patients are enrolled in a self-paid, university-based, outpatient weight loss program. All are prescribed VLCD (500-800 Cal/day), an exercise regimen, and group behavioral counseling. Black and white patients are matched for age, weight, body mass index, and by metabolic syndrome (MS) status.

RESULTS

A total of 304 black and white women (152 in each group) were included the analysis. Approximately 40% of patients had MS (white women: 39.5%; black women: 41.2%). Mean baseline weights were similar. After 12 weeks, weight reduction of 9.97% was seen in white women and 9.02% drop was seen in black women (both P<0.0001). However, the degree of weight change was not different between the groups (P = 0.244). Marked improvements in fasting glucose, total cholesterol, LDL, triglyceride, and blood pressures (BP) were observed (all P<0.01); however, no difference between cohorts were seen. Patients with MS had higher baseline weight, BP, glucose and triglyceride levels when compared to patients without MS (all P<0.01). Significant reductions in % body fat were seen in white and black patients, independent of MS status.

CONCLUSION

Obese patients, independent of race, were able to achieve significant weight loss when enrolled in a structured outpatient program. Weight loss significantly correlated with all aspects of MS. Our results suggest that differences seen in past studies may be influenced by socioeconomic and behavioral factors rather than differences in physiological response to dieting.

Weight loss and race modulate nitric oxide metabolism in overweight women

Weight reduction is associated with a decrease in the risk of developing cardiovascular disease. We hypothesized that, given the central role of reactive oxygen and nitrogen species in vascular biology, changes in nitric oxide (NO) metabolism contribute to benefits of weight loss. In a controlled weight loss trial involving overweight (body mass index (BMI) = 27-30 kg/m(2)), otherwise healthy premenopausal Caucasian and African-American women, serum levels of nitrite and nitrate, as an index of NO production, and protein 3-nitrotyrosine and myeloperoxidase (MPO), as markers of inflammation, were determined. Testing was performed before and after reduction to normal body weight (BMI < 25) under standardized conditions, with controlled diet, and following 1 month of weight maintenance. After weight loss there was an increase in nitrite and nitrate, and levels were higher among African-American women relative to Caucasian counterparts. Whereas weight loss was associated with a decrease in 3-nitrotyrosine in Caucasian women, no change was observed among African-Americans. Furthermore, MPO levels increased in response to weight loss for African-Americans, but did not change in Caucasian women. These data indicate that vascular production of reactive nitrogen species can be modulated by race and weight loss and highlight important racial differences in these responses and are discussed in the context of risk for developing vascular disease.

Lipoprotein metabolism in patients with anorexia nervosa: a case-control study investigating the mechanisms leading to hypercholesterolaemia

Hypercholesterolaemia is a common finding in patients with anorexia nervosa (AN). To investigate the type, frequency and pathophysiological mechanisms of changes in lipoprotein metabolism in AN we performed a cross-sectional study in fifty-eight female patients (mean age 24.2 years, BMI 15.3 (sd 1.5) kg/m(2)) and fifty-eight healthy age-matched controls (CO; BMI 22.2 (sd 1.7) kg/m(2)). Total cholesterol and LDL-cholesterol were higher in AN (5.5 (sd 1.3) v. 5.0 (sd 0.8) mmol/l, P=0.023; 3.6 (sd 1.1) v. 3.2 (sd 0.7) mmol/l, P=0.025 respectively). LDL particles were significantly more enriched in cholesterol and triacylglycerol in AN. In multiple regression analysis with LDL-cholesterol as the dependent and BMI, total body fat ( %), lathosterol:cholesterol ratio (endogenous cholesterol synthesis), 7alpha-hydroxy-4-cholesten-3-one (bile acid synthesis), non-esterified glycerol, free triiodothyronine and free thyroxine as independent variables, BMI was the only significant predictor in CO (R(2) 0.36, overall P=0.001). In AN the variability of LDL-cholesterol was significantly predicted by total body fat, free thyroxine, BMI, free triiodothyronine and non-esterified glycerol (R(2) 0.55, overall P<0.001). Subgroup analysis between restricting (AN-R) and binge-eating-purging patients (AN-B) indicated that in AN-R changes in lipoproteins, BMI and total body fat were more pronounced. AN-R patients had lower bile acid synthesis than AN-B (P=0.02). We conclude that elevated cholesterol concentrations in AN are generally due to an increase in LDL-cholesterol, which is mostly determined by the severe loss of body fat and the resulting changes in thyroid hormones, increased lipolysis and decreased endogenous cholesterol synthesis with resulting decrease in LDL removal. The clinical subtype of AN plays a major role in the mechanisms leading to hypercholesterolaemia.

Diet-induced weight loss is associated with an improvement in beta-cell function in older men

Although weight loss in older subjects has been shown to improve insulin sensitivity, it is unclear what effect this lifestyle intervention has on beta-cell function. To determine whether diet-induced weight loss can improve beta-cell function in older subjects, we studied 19 healthy male subjects (age, 65.4 +/- 0.9 yr; body mass index, 30.9 +/- 0.6 kg/m2; mean +/- SEM) before and after a 3-month 1200-kcal/d diet. The insulin sensitivity index (SI) was quantified using Bergman's minimal model. The acute insulin response to glucose (AIRg) and the maximal glucose-potentiated insulin response (AIRmax) were determined and then adjusted for SI (SI x AIRg and SI x AIRmax), thus providing measures of beta-cell function. Subjects demonstrated significant weight loss (95.6 +/- 2.4 to 86.1 +/- 2.5 kg; P < 0.001). Both fasting plasma glucose [97.3 +/- 1.6 to 95.1 +/- 1.3 mg/dl (5.4 +/- 0.09 to 5.3 +/- 0.07 mM); P = 0.05] and insulin [18.5 +/- 1.3 to 12.2 +/- 1.0 microU/ml (110.9 +/- 7.7 to 73.5 +/- 5.9 pM); P < 0.001] levels decreased. With weight loss, SI increased [1.59 +/- 0.24 to 2.49 +/- 0.32 x 10(-4) min(-1)/(microU/ml) (2.65 +/- 0.4 to 4.15 +/- 0.5 x 10(-5) min(-1)/pM); P < 0.001], whereas both AIRg [63.4 +/- 13.4 to 51.0 +/- 10.7 microU/ml (380 +/- 80 to 306 +/- 64 pM); P < 0.05] and AIRmax [314 +/- 31.4 to 259.9 +/- 33.4 microU/ml (1886 +/- 188 to 1560 +/- 200 pM); P < 0.05] decreased. Overall beta-cell function improved (SI x AIRg, 9.63 +/- 2.28 to 12.78 +/- 2.58 x 10(-3) min(-1), P < 0.05; and SI x AIRmax, 51.01 +/- 9.2 to 72.69 +/- 13.4 x 10(-3) min(-1), P < 0.05). Thus, the weight loss-associated improvements in both insulin sensitivity and beta-cell function may explain the beneficial effects of a lifestyle intervention on delaying the development of diabetes in older subjects.

A long-term high-protein diet markedly reduces adipose tissue without major side effects in Wistar male rats

Although there is a considerable interest of high-protein, low-carbohydrate diets to manage weight control, their safety is still the subject of considerable debate. They are suspected to be detrimental to the renal and hepatic functions, calcium balance, and insulin sensitivity. However, the long-term effects of a high-protein diet on a broad range of parameters have not been investigated. We studied the effects of a high-protein diet in rats over a period of 6 mo. Forty-eight Wistar male rats received either a normal-protein (NP: 14% protein) or high-protein (HP: 50% protein) diet. Detailed body composition, plasma hormones and nutrients, liver and kidney histopathology, hepatic markers of oxidative stress and detoxification, and the calcium balance were investigated. No major alterations of the liver and kidneys were found in HP rats, whereas NP rats exhibited massive hepatic steatosis. The calcium balance was unchanged, and detoxification markers (GSH and GST) were enhanced moderately in the HP group. In contrast, HP rats showed a sharp reduction in white adipose tissue and lower basal concentrations of triglycerides, glucose, leptin, and insulin. Our study suggests that the long-term consumption of an HP diet in male rats has no deleterious effects and could prevent metabolic syndrome.

Indexes of insulin resistance and secretion in obese children and adolescents: a validation study

OBJECTIVE

To assess the concurrent validity of fasting indexes of insulin sensitivity and secretion in obese prepubertal (Tanner stage 1) children and pubertal (Tanner stages 2-5) adolescents using estimates from the modified minimal model frequently sampled intravenous glucose tolerance test (FSIVGTT) as a criterion measure.

RESEARCH DESIGN AND METHODS

Eighteen obese children and adolescents (11 girls and 7 boys, mean age 12.2 +/- 2.4 years, mean BMI 35.4 +/- 6.2 kg/m(2), mean BMI-SDS 3.5 +/- 0.5, 7 prepubertal and 11 pubertal) participated in the study. All participants underwent an insulin-modified FSIVGTT on two occasions, and 15 repeated this test a third time (mean 12.9 and 12.0 weeks apart). S(i) measured by the FSIVGTT was compared with homeostasis model assessment (HOMA) of insulin resistance (HOMA-IR), quantitative insulin-sensitivity check index (QUICKI), fasting glucose-to-insulin ratio (FGIR), and fasting insulin (estimates of insulin sensitivity derived from fasting samples). The acute insulin response (AIR) measured by the FSIVGTT was compared with HOMA of percent beta-cell function (HOMA-beta%), FGIR, and fasting insulin (estimates of insulin secretion derived from fasting samples).

RESULTS

There was a significant negative correlation between HOMA-IR and S(i) (r = -0.89, r = -0.90, and r = -0.81, P < 0.01) and a significant positive correlation between QUICKI and S(i) (r = 0.89, r = 0.90, and r = 0.81, P < 0.01) at each time point. There was a significant positive correlation between FGIR and S(i) (r = 0.91, r = 0.91, and r = 0.82, P < 0.01) and a significant negative correlation between fasting insulin and S(i) (r = -90, r = -0.90, and r = -0.88, P < 0.01). HOMA-beta% was not as strongly correlated with AIR (r = 0.60, r = 0.54, and r = 0.61, P < 0.05).

CONCLUSIONS

HOMA-IR, QUICKI, FGIR, and fasting insulin correlate strongly with S(i) assessed by the FSIVGTT in obese children and adolescents. Correlations between HOMA-beta%, FGIR and fasting insulin, and AIR were not as strong. Indexes derived from fasting samples are a valid tool for assessing insulin sensitivity in prepubertal and pubertal obese children.

Effects of equal weight loss with orlistat and placebo on body fat and serum fatty acid composition and insulin resistance in obese women

BACKGROUND

Dietary fat has been reported to influence insulin sensitivity.

OBJECTIVE

The objective of the study was to determine how identical weight loss (target: loss of 8% of body weight over 3-6 mo) in women taking orlistat or placebo combined with a hypocaloric diet influences body composition and insulin sensitivity.

DESIGN

Forty-seven obese women [body mass index (in kg/m(2)): 32.1 +/- 0.4] were randomly assigned to receive either orlistat (120 mg 3 times daily; n = 23) or placebo (n = 24) with a hypocaloric diet. Whole-body insulin sensitivity (insulin clamp technique), serum fatty acids, and body composition (magnetic resonance imaging) were measured before and after weight loss.

RESULTS

The groups did not differ significantly at baseline with respect to age, body weight, intraabdominal and subcutaneous fat volumes, or insulin sensitivity. Weight loss did not differ significantly between the orlistat (7.3 +/- 0.2 kg, or 8.3 +/- 0.1%) and placebo (7.4 +/- 0.2 kg, or 8.2 +/- 0.1%) groups. Insulin sensitivity improved significantly (P < 0.001) and similarly after weight loss in the orlistat (from 4.0 +/- 0.3 to 5.1 +/- 0.3 mg x kg fat-free mass(-1) x min(-1)) and placebo (from 4.4 +/- 0.4 to 5.4 +/- 0.4 mg x kg fat-free mass(-1) x min(-1)) groups. Intraabdominal fat and subcutaneous fat decreased significantly in both groups, but the ratio of the 2 decreased significantly only in the orlistat group. The proportion of dihomo-gamma-linolenic acid (20:3n-6) in serum phospholipids was inversely related to insulin sensitivity both before (r = -0.48, P < 0.001) and after (r = -0.46, P < 0.001) weight loss, but it did not change significantly in either group.

CONCLUSIONS

Weight loss rather than inhibition of fat absorption enhances insulin sensitivity. A decrease in fat absorption by orlistat appears to favorably influence the ratio between intraabdominal and subcutaneous fat, which suggests that exogenous fat or its composition influences fat distribution.