Do leptin levels predict weight gain?--A 5-year follow-up study in Mauritius. Mauritius Non-communicable Disease Study Group

Circadian variation of serum leptin and adipose tissue changes in children

BACKGROUND

Higher morning serum leptin values are associated with larger adipose tissue gains in children; however, it is unclear if leptin circadian variation is itself associated with adipose tissue changes during growth.

OBJECTIVE

We studied the association of circadian variation in leptin with change in total body fat mass (TBFM), total body percentage fat (%FM), and trunk fat mass (TrFM).

METHODS

Baseline serum samples for leptin were obtained every 3 h for 24 h from 130 children (baseline age 9.6 ± 2.5y; 51.1% male; BMI-Z 1.59) with mean follow-up of 11.1 ± 4.0y and underwent dual-energy x-ray absorptiometry. ANCOVA models examined change in TBFM, %FM, or TrFM as dependent variables and number of years of follow-up, sex, race, baseline age, pubertal status, initial visit body composition, and initial visit serum leptin circadian variables (maximal diurnal leptin [acrophase], diurnal amplitude, and percentage change of amplitude) as independent factors.

RESULT

Although initial visit mesor (24 h average) leptin was positively associated with initial visit TBFM (r2  = 0.78, p < 0.001), %FM (r2  = 076, p < 0.001), and TrFM (r2  = 0.71, p < 0.001), none of the circadian leptin variables studied was significantly associated with change in TBFM, %FM, or TrFM.

CONCLUSION

We found no evidence that circadian variation in serum leptin concentrations during childhood is associated with long-term changes in children's adiposity.

Leptin and Leptin-to-Adiponectin Ratio Predict Adiposity Gain in Nonobese Children over a Six-Year Period

BACKGROUND

Previous longitudinal studies have shown inconsistent results regarding the influence of adipokines on changes in weight and body fat. We aimed to determine the predictive value of serum leptin, adiponectin, and their ratio on subsequent changes in obesity measures in children.

METHODS

Two hundred forty-six obese and 532 nonobese children aged 6-11 years were remeasured for BMI and waist circumference after 6.4 ± 0.2 years. Z-score of BMI was used to standardize for age and sex. Obesity was defined using the international BMI cutoffs. Waist-to-height ratio (WHtR) was calculated to define central obesity using a boundary value of 0.5. Fasting serum leptin and adiponectin levels were measured at baseline.

RESULTS

Newly identified obese children had significantly higher levels of leptin and leptin-to-adiponectin ratio than nonobese children. There were lower adiponectin levels in boys with persistent obesity versus those with transient obesity. After adjusting for age, Tanner stage, and corresponding adiposity measures at baseline, leptin levels and leptin-to-adiponectin ratio were positively associated with BMI Z-score gain in girls and WHtR gain in boys. An inverse association between leptin and BMI Z-score gain was detected in boys. Stratified analyses revealed significant associations only in the nonobese and prepubertal group. There were no significant associations between adiponectin and changes in obesity measures.

CONCLUSIONS

High leptin levels and leptin-to-adiponectin ratio are sex-specific predictors of obesity measures gain in nonobese and prepubertal children. Body composition measurement is necessary to assess fat mass growth and distribution during childhood and adolescence.

Leptin, adiponectin, and short-term and long-term weight loss after a lifestyle intervention in obese children

OBJECTIVE

In overweight children, high leptin levels are independently associated with higher risk for cardiovascular disease, whereas adiponectin seems to be protective against type 2 diabetes and atherosclerosis. The study examines the predictive value of leptin for weight loss after a 4- to 6-wk inpatient therapy and again after 1 y; as well as the association among weight loss, leptin, and adiponectin levels and changes in cardiometabolic risk factors after therapy.

METHODS

Body mass index (BMI), blood pressure, Tanner stage, and cardiometabolic risk factors were studied in 402 children (59.2% females, 13.9 ± 2.3 y, BMI 33.8 ± 5.7 kg/m(2)) before and after a 4-to 6-wk inpatient intervention (exercise, diet, and behavioral therapy) and BMI 1 y later (n = 206).

RESULTS

BMI was reduced from 33.8 ± 5.7 to 30.5 ± 5.1 kg/m(2) (P < 0.001) during the lifestyle intervention and remained unchanged after 1 y. Baseline BMI was positively associated with leptin (r = 0.60; P < 0.001) and cardiometabolic risk factors (blood pressure, high-density lipoprotein [HDL] cholesterol, triglycerides). Baseline leptin was associated with BMI and triglycerides (r = 0.39; P < 0.001), baseline adiponectin with HDL-cholesterol (r = 0.40; P < 0.001). Baseline BMI explained 40.7% of the variance in weight loss during therapy. The combination of BMI, sex, and leptin explained 50.4% of the variance. Neither BMI nor leptin predicted weight changes over the long term.

CONCLUSIONS

Overweight children maintained a substantial amount of weight loss after participation in a short-term inpatient lifestyle intervention. Baseline BMI was positively associated with weight reduction during the intervention, whereas baseline leptin had only a minor predictive value.

Candidate molecular pathway genes related to appetite regulatory neural network, adipocyte homeostasis and obesity: results from the CARDIA Study

Appetite regulatory neural network and adipocyte homeostasis molecular pathways are critical to long-term weight maintenance. Associations between obesity-related phenotypes and four genes in these pathways - leptin (LEP), leptin receptor (LEPR), neuropeptide Y2 receptor (NPY2R) and peptide YY (PYY) were examined in CARDIA Study participants (aged 18-30 at recruitment in 1985-6). Weight, BMI and waist circumference were measured at baseline and at years 2, 5, 7, 10, 15, and 20. Genotyping was conducted using tag SNPs characterising common genetic variations in these genes. Generalized estimating equation (GEE) models estimated associations between SNPs and repeated anthropometric measurements, controlling for sex and age. False discovery rate was used to adjust for multiple testing. In African-Americans, SNPs across the LEP gene demonstrated significant overall associations with all obesity-related phenotypes. The associations between LEP rs17151919 with weight tended to strengthen with time - the difference in weight associated with each additional minor allele increased from 2.6 kg at baseline to 4.8 kg at year 20 (SNP*time interaction p = 0.0193). NPY2R gene SNPs were associated with waist circumference among African-American men (p = 0.0462). In Caucasians, LEP SNPs also tended to be associated with weight (p = 0.0471), and PYY rs11684664 was associated with obesity-related phenotypes in women only (p = 0.010-0.026). Several LEP, and NPY2R and PYY SNPs were associated with obesity-related phenotypes in young adults, particularly among African-Americans.

Prospective investigation of metabolic characteristics in relation to weight gain in older adults: the Hoorn Study

The objective of this investigation was to determine the relation between baseline glucose, insulin, adiponectin, and leptin levels and subsequent 6-year weight and waist change in older men and women without diabetes in a prospective cohort study. Participants were 1,198 Dutch men and women without diabetes who were aged 50-77 years when baseline metabolic and anthropometric measurements were evaluated (1989-1991). Approximately 6 years later, body weight and waist circumference were re-measured at a follow-up examination (1996-1998). Metabolic variables (fasting plasma glucose, 2-h postchallenge plasma glucose, homeostasis model assessment of insulin resistance (HOMA-IR), adiponectin, and leptin) were evaluated as predictors of changes in weight and waist circumference. Postchallenge plasma glucose (mmol/l) significantly predicted less gain in both weight and waist circumference (beta = -0.28 kg, s.e. = 0.11; beta = -0.31 cm, s.e. = 0.14, respectively) during follow-up. Leptin (microg/l) significantly predicted greater increases in weight (beta = 0.29 kg, s.e. = 0.07) and waist (beta = 0.16 cm, s.e. = 0.08) among men and in waist among women (beta = 0.06 cm, s.e. = 0.02). Fasting plasma glucose (mmol/l) predicted an increase in waist among women (beta = 1.59 cm, s.e. = 0.63), but not in men (beta = -0.74 cm, s.e. = 0.55). Adiponectin and insulin did not predict weight or waist change. The authors conclude that lower postchallenge plasma glucose and higher fasting leptin levels significantly predicted long-term increases in weight and waist circumference. In contrast, measures of insulin resistance and adiponectin were not associated with weight change in this cohort of older persons without diabetes.

Influence of serum leptin on weight and body fat growth in children at high risk for adult obesity

OBJECTIVE

Our objective was to examine serum leptin prospectively as a predictor of weight and body fat growth in children at high risk for adult obesity. We hypothesized that leptin measurements would be positively associated with increased growth of adipose tissue because children with high baseline leptin for their body fat mass have greater leptin resistance and thus would have greater susceptibility to weight gain.

METHODS

Children ages 6-12 yr at high risk for adult obesity because of early-onset childhood overweight and/or parental overweight were recruited from 1996-2004. Growth in body mass index (BMI) was studied in 197 children, and growth in total body fat mass was examined in 149 children over an average follow-up interval of 4.4 yr (range, 1-8 yr). Longitudinal analyses accounted for sex, race, socioeconomic status, initial body composition, age, skeletal age, and physical activity and included all available interim visits for each individual so that a total of 982 subject visits were included in the analysis.

RESULTS

At baseline, 43% of children studied were overweight (BMI > or = 95th percentile); during follow-up, an additional 14% became overweight. Independent of initial body composition, baseline leptin was a statistically significant positive predictor of increased BMI (P = 0.0147) and increased total body fat mass (P < 0.007).

CONCLUSIONS

High serum leptin, independent of body fat, may be an indicator of increased leptin resistance, which predisposes children at high risk for adult obesity to somewhat greater growth in weight and body fat during childhood.

High plasma leptin predicts an increase in subcutaneous adiposity in children and adults

OBJECTIVE

To investigate the hypothesis that plasma leptin may predict adiposity changes.

DESIGN

A population-based cohort study.

SETTING

Fleurbaix and Laventie, in the north of France.

SUBJECTS

In all, 1175 subjects participated, of whom 946 completed measurements at baseline (1999) and follow-up (2001). After excluding 64 subjects obese at baseline, 882 subjects (478 adults, 404 children 8 years and over) were included in the analysis.

INTERVENTIONS

We measured plasma leptin concentrations at baseline and various adiposity parameters at baseline and follow-up. Partial correlation coefficients (r(p)) between baseline plasma leptin and each adiposity indicator at follow-up were calculated with adjustment for baseline age, pubertal stage, adiposity and familial correlations between siblings.

RESULTS

Changes in body mass index and percentage body fat were not related to baseline plasma leptin. High baseline plasma leptin predicted an increase (r(p) (P-value)) in the sum of the four skinfolds (0.18 (<0.0001)), the waist circumference (0.16 (0.0003)) and the waist-to-hip ratio (0.29 (<0.0001)) in adults only, and in the hip circumference in adults (0.20 (<0.0001)) and children (0.22 (<0.0001)). After adjustment for a set of four adiposity variables at baseline (percentage body fat, skinfolds, waist and hip circumferences), baseline plasma leptin predicted only changes in the sum of the four skinfolds in adults (0.15 (0.001)), with similar tendency although not significant in children (0.08 (0.13)).

CONCLUSIONS

A high leptin relative to baseline fat mass predicts fat mass gain over time, mainly in the subcutaneous location.

Brain adipocytokine action and metabolic regulation

Adipose tissue secretes factors that control various physiological systems. The fall in leptin during fasting mediates hyperphagia and suppresses thermogenesis, thyroid and reproductive hormones, and immune system. On the other hand, rising leptin levels in the fed state stimulate fatty acid oxidation, decrease appetite, and limit weight gain. These divergent effects of leptin occur through neuronal circuits in the hypothalamus and other brain areas. Leptin also regulates the activities of enzymes involved in lipid metabolism, e.g., AMP-activated protein kinase and stearoyl-CoA desaturase-1, and also interacts with insulin signaling in the brain. Adiponectin enhances fatty acid oxidation and insulin sensitivity, in part by stimulating AMP-activated protein kinase phosphorylation and activity in liver and muscle. Moreover, adiponectin decreases body fat by increasing energy expenditure and lipid catabolism. These effects involve peripheral and possibly central mechanisms. Adipose tissue mediates interconversion of steroid hormones and secretes proinflammatory cytokines, vasoactive peptides, and coagulation and complement proteins. Understanding the actions of these "adipocytokines" will provide insight into the pathogenesis and treatment of obesity and related diseases.

The entero-insular axis and adipose tissue-related factors in the prediction of weight gain in humans

Obesity has now reached epidemic proportions. Epidemiological studies in the past decades have shown that adults gain weight and adiposity from the early twenties until their sixties. In the paediatric population, growing numbers of children and adolescents put on unhealthy weight. Many environmental, socio-economical and biological determinants that predispose to weight gain have been identified thus far. The aim of the present review is to summarize the current knowledge on the role of the circulating levels of adipokines and other entero-insular hormones and biological markers of obesity to predict weight gain in humans. The review focuses on relationship between hormonal and biochemical markers (insulin, insulin-like growth factors, gastrointestinal hormones, leptin, adiponectin, resistin, inflammatory proteins and cytokines) and weight gain in prospective studies. The complex relationships displayed by these hormonal factors with future weight gain in humans are critically reviewed and integrative models are proposed. Overall, most of the studies reported to date made adjustments for baseline body mass index but failed to consider dietary intake and physical activity as confounding factors. Outstanding questions are raised and new directions for future prospective studies are proposed in order to improve our understanding of the role of biological determinants of energy balance and development of obesity in humans.

Ghrelin, adiponectin, and leptin do not predict long-term changes in weight and body mass index in older adults: longitudinal analysis of the Rancho Bernardo cohort

Ghrelin, leptin, and adiponectin are associated with body size in cross-sectional studies; it is unknown whether these hormones predict long-term changes in body size. Multilevel models were used to study associations between fasting serum hormones, measured in 698 men and 619 women (60-91 years) in samples collected at baseline (1984-1987), and changes in weight and body mass index, assessed repeatedly over a follow-up period of up to 18 years (median, 4.7 years). Baseline weight was -1.5 kg lower for a one-standard-deviation increment in ghrelin and -3.3 kg lower for a one-standard-deviation increment in adiponectin, similar in men and women. For leptin, baseline weight was 12.1 kg higher for a one-standard-deviation increment in men, compared with 5.7 kg in women (sex-interaction p < or = 0.0001). Ghrelin and adiponectin did not affect weight change; their associations with weight were constant over time, indicated by nonsignificant hormone-by-time interactions. The positive association between leptin and weight became slightly weaker over time. Results were similar when investigating repeated measures of body mass index. From this analysis of Rancho Bernardo Study data, the authors conclude that ghrelin, adiponectin, and leptin do not predict weight gain beyond reflecting the influence of attained body size on future changes in weight or body mass index.

Leptin predicts a worsening of the features of the metabolic syndrome independently of obesity

OBJECTIVE

The term metabolic syndrome (MS) describes a cluster of cardiovascular risk factors including dyslipidemia, glucose intolerance, insulin resistance, and hypertension. Obesity increases the risk of MS, but as obesity is neither necessary nor sufficient to cause the syndrome, there is considerable interest in identifying obesity-independent pathways. One such pathway may involve the actions of the adipokine leptin, which is associated cross-sectionally with MS and prospectively with coronary heart disease and stroke, independently of obesity. Our goal was to test the hypothesis that leptin predicts the development of the features of MS independently of obesity.

RESEARCH METHODS AND PROCEDURES

This study used a prospective population-based cohort of 748 middle-aged whites in whom baseline measures of leptin and repeated measurement of the subcomponents of the MS at 5 and 10 years were available. The features of the MS were characterized as five factors (obesity, dyslipidemia, elevated blood pressure, glucose intolerance, and insulin resistance), which were combined to create an MS summary score.

RESULTS

Baseline leptin significantly predicted the development of obesity (p = 0.001) and, after adjustment for BMI, development of glucose intolerance (p = 0.016) and insulin resistance (p < 0.0001). Leptin levels did not independently predict a change in lipids or blood pressure. Leptin levels significantly predicted the development of the MS (p = 0.036), independently of baseline BMI.

DISCUSSION

Leptin predicts the development of the MS independently of baseline obesity. This association is specifically related to the development of glucose intolerance and insulin resistance. The extent to which these relationships are explained through residual confounding by obesity remains to be determined.

A study of linkage and association of body mass index in the Old Order Amish

Obesity is thought to have a genetic component with the estimates of heritability ranging from 0.25-0.40. As part of an ongoing study of obesity in the Old Order Amish, seven two- and three-generation families (157 individuals) were assessed for 21 traits related to obesity, including body mass index (BMI) and BMI-percentile (a standardized distribution of BMI adjusted for age and sex). Genotyping was performed using a panel of 384 short-tandem repeat markers. In this sample, the estimates of heritability ranged from 0.16-0.31 for BMI and from 0.40-0.52 for BMI-percentile. Model-independent linkage analysis identified candidate regions on chromosomes 1, 5, 7, 8, and 11. Given that several markers on 7q were significant for both BMI and BMI-percentile (P < or = 0.001) and that the structural locus for leptin was located on 7q, this region was considered to be the primary candidate region. Subsequent typing of additional flanking markers on 7q corroborated the original findings. Tests of intrafamilial association for alleles at markers in this candidate region were significant at similar levels. Although there is some evidence for linkage and association in the region containing leptin, there appears to be stronger evidence for linkage (P < or = 0.001) and association (P < or = 0.00001) with BMI in a region 10-15 cM further downstream of leptin, flanked by markers D7S1804 and D7S3070 with peak values from D7S495-D7S1798. Evidence from linkage and association studies suggests that this region (D7S1804-D7S3070) may be responsible, at least in part, for variation in BMI and BMI-percentile in the Old Order Amish.

Leptin and insulin responses to a four-day energy-deficient diet in men with different weight history

OBJECTIVE

To assess the leptin responses to a 4-day energy-restricted diet in men with different weight history; high retrospective weight gain was expected to be associated with a small decline in leptin.

DESIGN

Changes in fasting leptin and insulin were measured during a 4-day controlled intervention, in which men with high retrospective weight gain and men who had stable weight consumed 35% of their estimated energy needs.

SUBJECTS

A total of 44 healthy men (age: 31-52 y, BMI: 22.7-39.8 kg/m(2)) were recruited from a cohort study: 22 men who had gained weight (weight change >1 kg/y) and 22 men whose weight had remained stable (weight change +/-0.3 kg/y) between the first (1987-1991) and the second measurement (1993-1997) of the cohort study. The intervention study was carried out in 2001.

RESULTS

After intervention, changes in fasting leptin levels were similar for both groups of retrospective weight gain: -2.2 microlU/ml (95% CI: -2.8; -1.7) and -2.4 microlU/ml (95% CI: -3.2; -1.7) respectively (P=0.69). Proportional changes in fasting leptin levels were different: -43.3% (95% CI: -47.8; -38.4) in the participants whose weight had remained stable (n=22) and -35.2% (95% CI: -42.4; -27.1) in those who had gained weight (n=22)(P<0.05). Analyses in a subgroup of men (n=18), in which the contrast in weight history was more pronounced than in the total group, did not show this difference. A higher proportional decrease in insulin levels was seen in men whose weight remained stable than in those who had gained weight: -35.4% (95% CI: -46.9; -21.3) and -12.8% (95% CI: -28.1; 5.7), respectively. The proportional decrease in leptin was positively associated with the proportional decrease in insulin (r=0.52; P<0.05). The decrease in leptin was positively associated with preintervention body weight (r=0.36; P<0.05), BMI (r=0.44; P<0.05), and waist-circumference (r=0.46; P<0.05).

CONCLUSION

Although we found that the 4-day energy restriction had a smaller effect on the decrease in leptin in men with retrospective weight gain, our study does not show convincing evidence that men who gained weight are less leptin responsive to changes in energy balance than those who were weight stable.

Genetic variation in the leptin receptor gene, leptin, and weight gain in young Dutch adults

OBJECTIVE

To investigate the association between leptin levels, polymorphisms in the leptin receptor (LEPR) gene, and weight gain.

RESEARCH METHODS AND PROCEDURES

From two large prospective cohorts in The Netherlands (n = 17,500), we compared the baseline leptin of 259 subjects who had gained an average of 12.6 kg (range 5.5 to 33 kg) with 277 subjects who kept stable weight (range -2.6 to 3.1 kg) after a mean follow-up of 6.8 years. Three polymorphisms in the LEPR gene (Lys109Arg, Gln223Arg, and Lys656Asn) were determined.

RESULTS

Weight gainers had significantly higher baseline leptin levels than those who kept stable weight (odds ratio = 1.27, 95% confidence interval 1.1 to 1.5, per SD increase in log(e)-transformed leptin). Weight gainers with the Arg109 or the Arg223 alleles had higher leptin levels compared with the noncarriers of these alleles. Only among men, the association between leptin and weight gain tended to be stronger among those with an Arg223 allele compared with those without this mutation.

DISCUSSION

Relatively high leptin levels predict weight gain, suggesting that leptin resistance plays a role in the development of obesity in the general population. Higher leptin levels for those with a Lys109Arg or Gln223Arg mutation (or a linked other marker) may imply that these subjects have a modified functional leptin receptor. However, the role of these mutations on weight gain is limited.

Contribution of weight cycling to serum leptin in human obesity

OBJECTIVE

To investigate to what extent serum leptin concentrations in obese humans are influenced by a history of weight cycling.

DESIGN

Cross-sectional study on serum leptin concentrations and body composition in a cohort of obese subjects in whom a retrospective recall of weight and diet history was made.

SUBJECTS

One hundred and twenty-eight obese patients (89 females and 39 males), aged 18-61 y, body mass index (BMI) 31.2-63.4 kg/m(2).

MEASUREMENTS

Serum leptin; various fatness and fat distribution parameters (by anthropometry and bioelectrical impedance analysis); history of overweight at puberty; number, magnitude and timing of previous diet episodes and of consequent weight regain by interview.

RESULTS

By univariate analysis, serum leptin concentrations were significantly correlated with weight, waist-hip ratio, percentage body fat, maximal percentage weight loss in a single diet episode, cumulative percentage weight loss in all diet episodes, cumulative weight regained in all diet episodes, but not with the number of diet episodes. All correlations related to anthropometric and body composition parameters were stronger for men, compared to women, although the male subgroup was smaller. On the contrary, there was a strong positive correlation between weight cycling parameters and serum leptin in women but not in men. Leptin concentrations were significantly higher in patients who were overweight at puberty than in those who were not overweight at puberty. After correction for percentage body fat, presence of overweight at puberty did not correlate any longer with leptin concentrations in either gender. In women, cumulative percentage weight loss in all diet episodes contributed an additional 5% to the variance of serum leptin in the overall model.

CONCLUSION

The positive correlation between weight cycling and leptin concentration in obesity is mainly accounted for the higher percentage body fat in obese weight cyclers, although in women weight cycling per se independently contributes to the variance of serum leptin.

Influence of leptin on changes in body fat during growth in African American and white children

OBJECTIVE

The aim of this study was to determine whether initial levels or temporal changes in fasting leptin were associated with longitudinal changes in body-fat mass in children.

RESEARCH METHODS AND PROCEDURES

The study group consisted of 85 children (42 white and 43 African American) with a mean initial age of 8.1 +/- 0.1 years. The children had between three and six annual visits for repeated measurements of body composition by DXA and fasting leptin level. Fat mass and fasting leptin level were not normally distributed and were log-transformed. Data were analyzed using SAS Proc mixed growth models, with log fat as the dependent variable.

RESULTS

Initial leptin level was a significant predictor of the change in fat mass over time (p < 0.0001), with high initial leptin levels resulting in increased fat gain, independent of initial fat levels. This relationship remained significant when the data were analyzed separately by race (whites, p < 0.0001; African Americans, p = 0.008). The relationship between the initial level of leptin and the change in fat mass was not modified by race, sex, or Tanner Stage. The rate of change in leptin during the study was significantly related to the rate of change in fat mass in African Americans (p = 0.008) but not in whites (p = 0.490).

DISCUSSION

In conclusion, high fasting leptin level at the start of the study was significantly associated with increasing fat mass in this cohort, indicating that the children may be developing resistance to the effects of leptin.

Leptin concentrations in the United States: relations with demographic and anthropometric measures

BACKGROUND

Leptin is a peptide that is strongly correlated with adiposity and is a potential determinant of obesity and its complications.

OBJECTIVE

Leptin concentrations from a representative sample of the US population were examined in relation to demographic and anthropometric measures.

DESIGN

Fasting serum leptin concentrations were measured in 6303 women and men aged > or =20 y in the third National Health and Nutrition Examination Survey. Anthropometric measures included body mass index, 4 skinfold thicknesses, and 4 body circumferences. Ethnic groups included non-Hispanic whites and blacks and Mexican Americans.

RESULTS

The mean serum leptin concentration was much higher in women (12.7 microg/L) than in men (4.6 microg/L). In a multivariate analysis, leptin concentrations were associated with the sum of 4 skinfold thicknesses, waist and hip circumferences, ethnicity, and age. These measures explained most of the variance in leptin concentrations in women (R2 = 0.69) and in men (R2 = 0.67). Triceps skinfold thickness, when substituted for the sum of skinfold thicknesses, performed nearly as well in women (R2 = 0.68) and men (R2 = 0.67). Leptin concentrations were slightly but significantly higher in non-Hispanic blacks than in non-Hispanic whites of both sexes when these anthropometric measures and age were controlled for; Mexican Americans had concentrations that were intermediate compared with the concentrations of non-Hispanic whites and blacks.

CONCLUSIONS

In this large, representative sample of the US population, demographic and anthropometric measures predicted serum leptin concentrations in women and men.

Leptin serum concentrations predict the responsiveness of obese children and adolescents to weight excess reduction program

BACKGROUND

A role for leptin to predict weight gain is still controversial.

OBJECTIVE AND DESIGN

To determine the relationship between baseline serum leptin values and responsiveness to an educational-based weight excess reduction program (WERP), 418 (241 males and 185 females) obese subjects, aged 9-15 y, were recruited. WERP required 2 y of follow-up. Body mass index (BMI) was evaluated at baseline and at each semester of follow-up. The obese subjects were subdivided into responsives and non-responsives, according to reduction or not of their BMI Z-scores during the WERP. Leptin concentrations were assayed at baseline and were included together with other independent variables in statistical multiple regression analysis.

RESULTS

At a preliminary multiple regression analysis, a significant positive correlation between leptin values and BMI Z-score reduction at the second, third and fourth semester of follow-up was registered. To determine the odds ratio of the subjects who were responsive or non-responsive at the various semesters of WERP follow-up, a stepwise logistic regression was used incorporating the same predictors, with the serum leptin values subdivided into quintiles and responsiveness and non-responsiveness as a binary outcome variable. The model offered a satisfying goodness of fit as shown by the sensitivity and specificity. The odds ratio of being responsive were significantly increased by greater quintiles of leptin serum concentrations. Furthermore, such odds ratios were much higher in pubertal than in prepubertal subjects.

CONCLUSIONS

These findings support a significant role for serum leptin concentration in predicting BMI changes as a response to an educational excess weight reduction program.

Percent body fat and lean mass explain the gender difference in leptin: analysis and interpretation of leptin in Hispanic and non-Hispanic white adults

OBJECTIVE

To reassess the relationship between body fat and fasting leptin concentrations comparing plasma vs. serum assessments of leptin; ratios vs. regression adjustment for body composition; fat and lean mass vs. percent body fat; and gender-, ethnic-, and age-related variations.

RESEARCH METHODS AND PROCEDURES

Subjects included 766 adults from the nondiabetic cohort of the San Luis Valley Diabetes Study examined at follow up (1997 to 1998). Body composition was determined by dual energy X-ray absorptiometry. Leptin concentrations were determined after an overnight fast.

RESULTS

Fasting serum and plasma assessments of leptin were correlated with percent body fat to the same degree. Women had significantly higher serum leptin concentrations than men when leptin concentrations were divided by body mass index, fat mass in kilograms or percent body fat. The methodological problem inherent in interpreting these ratio measures is pictorially demonstrated. In regression analysis, fat mass alone did not explain the gender difference. However, lean body mass was inversely related to leptin concentrations (p < 0.0001) and explained 71% of the gender difference at a given fat mass. Percent body fat explained all of the gender difference in leptin concentrations in both Hispanics and non-Hispanic whites. Similar to findings about gender differences, ethnic- and age-related variations in the leptin-body fat association were minimized when percent body fat was employed as the body fat measure.

DISCUSSION

Regression analysis and percent body fat measured with dual energy X-ray absorptiometry are recommended when assessing the relationship between leptin and body fat. Gender differences in leptin concentrations were accounted for by percent body fat in free living (no diet control), Hispanic and non-Hispanic white adults.

Fibrinogen, other putative markers of inflammation, and weight gain in middle-aged adults--the ARIC study. Atherosclerosis Risk in Communities

PURPOSE

Weight gain is an important risk factor for the development of the metabolic syndrome, and inflammatory mediators are strongly associated with this syndrome. Our aim was to investigate whether inflammation predicts the development of weight gain in populations.

RESEARCH METHODS AND PROCEDURES

We investigated selected markers of inflammation in the prediction of weight gain over an approximately 3-year period in a biethnic cohort of 13,017 men and women, 45 to 64 years of age, using multiple linear and logistic regression modeling.

RESULTS

In adjusted models, those in the highest quartile of fibrinogen gained, during the first 3 years of follow-up, an estimated 0.23 kg/year more than those in the lowest quartile (p < 0.001). Adjusted odds of a large (greater than the 90th percentile) weight gain for those in the highest quartile of fibrinogen were 1.65 (95% confidence interval [CI], 1.38 to 1.97) times those in the lowest quartile. Similarly adjusted odds ratios for a large weight gain for those with high levels of white blood cell count, factor VIII, and von Willebrand factor were 1.38 (1.14 to 1.67), 1.28 (1.08 to 1.53), and 1.28 (1.08 to 1.51), respectively.

DISCUSSION

Fibrinogen and other putative markers of inflammation predict weight gain in middle-aged adults. Given the known links between the inflammatory response and intermediary metabolism and the methodological strengths of the Atherosclerosis Risk in Communities (ARIC) cohort, these findings, though without immediate clinical applicability, suggest that inflammatory processes play a role in the development of the metabolic syndrome and cardiovascular disease in part through stimulation of weight gain.

Low plasma leptin concentration and low rates of fat oxidation in weight-stable post-obese subjects

OBJECTIVE

A low resting metabolic rate for a given body size and composition, a low rate of fat oxidation, low levels of physical activity, and low plasma leptin concentrations are all risk factors for body weight gain. The aim of the present investigation was to compare resting metabolic rate (RMR), respiratory quotient (RQ), levels of physical activity, and plasma leptin concentrations in eight post-obese adults (2 males and 6 females; 48.9 +/- 12.2 years; body mass index [BMI]: 24.5 +/- 1.0 kg/m2; body fat 33 +/- 5%; mean +/- SD) who lost 27.1 +/- 21.3 kg (16 to 79 kg) and had maintained this weight loss for > or =2 months (2 to 9 months) to eight age- and BMI-matched control never-obese subjects (1 male and 7 females; 49.1 +/- 5.2 years; BMI 24.4 +/- 1.0 kg/m2; body fat 33 +/- 7%).

RESEARCH METHODS AND PROCEDURES

Following 3 days of weight maintenance diet (50% carbohydrate and 30% fat), RMR and RQ were measured after a 10-hour fast using indirect calorimetry and plasma leptin concentrations were measured using radioimmunoassay. Levels of physical activity were estimated using an accelerometer over a 48-hour period in free living conditions.

RESULTS

After adjustment for fat mass and fat-free mass, post-obese subjects had, compared with controls, similar levels of physical activity (4185 +/- 205 vs. 4295 +/- 204 counts) and similar RMR (1383 +/- 268 vs. 1430 +/- 104 kcal/day) but higher RQ (0.86 +/- 0.04 vs. 0.81 +/- 0.03, p < 0.05). Leptin concentration correlated positively with percent body fat (r = 0.57, p < 0.05) and, after adjusting for fat mass and fat-free mass, was lower in post-obese than in control subjects (4.5 +/- 2.1 vs. 11.6 +/- 7.9 ng/mL, p < 0.05).

DISCUSSION

The low fat oxidation and low plasma leptin concentrations observed in post-obese individuals may, in part, explain their propensity to relapse.

The role of leptin in human growth and puberty

Experimental animal studies demonstrate the effects of leptin on appetite, weight gain and metabolism. The biological effects of leptin in human adults are still to be determined, but recent reports show that congenital leptin deficiency leads to hyperphagia and excessive weight gain from early infancy as well as failure of pubertal onset in adolescence. Our recently reported data from two longitudinal cohorts suggest a role for leptin in the normal regulation of childhood weight gain, maturation and the development of secondary sexual features and body composition. Low leptin levels in cord blood closely reflected decreased adiposity at birth and strongly predicted high rates of weight gain in infancy and catch-up growth. In adolescents, leptin levels rose gradually with age prior to puberty, suggesting that a threshold effect may trigger puberty. In girls, low leptin levels at the start of puberty predicted large gains in the percentage of fat mass, perhaps suggesting a role in the preparation for childbearing.