Weight, adiposity, and physical activity as determinants of an insulin sensitivity index in pima Indian children

Fat-free/lean body mass in children with insulin resistance or metabolic syndrome: a systematic review and meta-analysis

BACKGROUND

Lean / Fat Free Body Mass (LBM) is metabolically involved in active processes such as resting energy expenditure, glucose uptake, and myokine secretion. Nonetheless, its association with insulin sensitivity / resistance / glucose tolerance and metabolic syndrome remains unclear in childhood.

METHODS

The current investigation aimed to examine the differences in fat-free mass /lean body mass according to the presence of insulin sensitivity/insulin resistance/glucose tolerance/metabolic syndrome in children. A systematic search was carried out in Medline/PubMed, Embase, Scopus, Web of Science, and SciELO, covering the period from each database's respective start to 21 June 2021. Two researchers evaluated 7111 studies according to the inclusion criteria: original human studies, written in English or Spanish, evaluating fat-free mass/lean body mass in children and adolescents including both with and without insulin sensitivity/insulin resistance /glucose tolerance and metabolic syndrome and reported the differences between them in terms of fat free mass/lean body mass. The results of the studies were combined with insulin sensitivity, insulin, resistance, glucose tolerance and metabolic syndrome. The standardized mean difference (SMD) in each study was calculated and combined using the random-effects model. Heterogeneity between studies was tested using the index of heterogeneity (I2), leave-one-out sensitivity analyses were performed, and publication bias was assessed using the Egger and Begg tests.

RESULTS

Finally, 15 studies which compared groups defined according to different glucose homeostasis criteria or metabolic syndrome out of 103 eligible studies were included in this systematic review and 12 studies in the meta-analysis. Meta-analysis showed lower fat-free mass/lean body mass percentage in participants with insulin resistance/glucose tolerance/metabolic syndrome (SMD -0.47; 95% CI, - 0.62 to - 0.32) while in mass units (kg), higher values were found in the same group (SMD, 1.01; 95% CI, 0.43 to 1.60).

CONCLUSIONS

Our results identified lower values of fat-free mass/lean body mass (%) in children and adolescents with insulin resistance/glucose tolerance/metabolic syndrome and higher values of fat-free mass/lean body mass when these are expressed in kg. The evidence of the impact of lean mass on children's glucose homeostasis or metabolic syndrome is limited, so future studies research should focus on explaining the effect of fat-free mass/lean body mass on different metabolic outcomes. Moreover, it may be interesting to evaluate the quality (muscle density) or functional (muscle strength) outcomes in addition to both absolute (kg) and relative (%) values in future studies. The systematic review was prospectively registered at PROSPERO (registration number CRD42019124734; available at: http://www.crd.york.ac.uk/prospero [accessed: 05 April 2019]).

Contribution of lower physical activity levels to higher risk of insulin resistance and associated metabolic disturbances in South Asians compared to Europeans

BACKGROUND

Insulin resistance and related metabolic disturbances are major risk factors for the higher T2D risk and associated morbidity and mortality amongst South Asians. The contribution of physical activity to the increased prevalence of insulin resistance and related disturbances amongst South Asians is unknown.

METHODS

We recruited 902 South Asian and European men and women, aged 35-85 years from the ongoing LOLIPOP study. Clinical characterisation comprised standardised questionnaire and measurement of height, weight, waist and hip circumference and blood pressure. Fasting bloods were taken for assessment of glucose, insulin, lipids and HbA1c. Physical activity was quantified using a validated accelerometer, Actigraph GT3X+, worn for 7 days. Univariate and multivariate approaches were used to investigate the relationship between ethnicity, physical activity, insulin resistance and related metabolic disturbances.

RESULTS

Total physical activity was ~31% (P = 0.01) lower amongst South Asians compared to Europeans (Mean MET.minutes [SD]: 1505.2 [52] vs. 2050.9 [86.6], P<0.001). After adjusting for age and sex, total physical activity had a negative association with HOMA-IR (B [SE]: -0.18 [0.08], P = 0.04) and fasting glucose levels (B[SE]: -0.11 [0.04], P = 0.02). There was no association between physical activity and other glycemic and lipid parameters. Total physical activity per week contributed towards the differences in insulin resistance and associated metabolic disturbances between South Asians and Europeans.

CONCLUSION

Lower levels of physical activity may contribute to the increased insulin resistance in South Asians compared to Europeans. Our results suggest that lifestyle modification through increased physical activity may help to improve glucose metabolism and reduce the burden of excess T2D and related complications amongst South Asians.

Preschool children's physical activity and cardiovascular disease risk: A systematic review

OBJECTIVES

Higher physical activity (PA) levels in adults are associated with lower cardiovascular disease risk, however it is unclear whether this association is evident in children younger than five years. Given that cardiovascular disease has early life origins, this study systematically reviews evidence of associations between PA and cardiovascular disease risk factors among children aged 3-5.5years.

DESIGN

Systematic review.

METHOD

A systematic search of multiple data bases was conducted to identify published papers reporting associations between any measure of PA and cardiovascular disease risk factors.

INCLUSION CRITERIA

English language; peer-reviewed; original quantitative research; mean age or majority of sample to be between 3.0-5.5years. Studies where the sample was characterised by a health condition (e.g. obese, hypertensive) were not eligible for inclusion.

RESULTS

Twelve papers met the inclusion criteria. At least one study for each cardiovascular disease risk factor except inflammation was included. PA was not associated with insulin resistance, and inconsistently associated with the remaining cardiovascular disease risk factors. Studies were mostly cross-sectional and methodologically heterogeneous. Longitudinal and experimental study designs and objective measurement of PA may help provide a clearer indication of the interplay between PA and cardiovascular disease risk in the preschool population.

From Sea to Shining Sea and the Great Plains to Patagonia: A Review on Current Knowledge of Diabetes Mellitus in Hispanics/Latinos in the US and Latin America

The past two decades have witnessed many advances in the prevention, treatment, and control of diabetes mellitus (DM) and its complications. Increased screening has led to a greater recognition of type 2 diabetes mellitus (type 2 DM) and prediabetes; however, Hispanics/Latinos, the largest minority group in the US, have not fully benefited from these advances. The Hispanic/Latino population is highly diverse in ancestries, birth places, cultures, languages, and socioeconomic backgrounds, and it populates most of the Western Hemisphere. In the US, the prevalence of DM varies among Hispanic/Latino heritage groups, being higher among Mexicans, Puerto Ricans, and Dominicans, and lower among South Americans. The risk and prevalence of diabetes among Hispanics/Latinos are significantly higher than in non-Hispanic Whites, and nearly 40% of Hispanics/Latinos with diabetes have not been formally diagnosed. Despite these striking facts, the representation of Hispanics/Latinos in pharmacological and non-pharmacological clinical trials has been suboptimal, while the prevalence of diabetes in these populations continues to rise. This review will focus on the epidemiology, etiology and prevention of type 2 DM in populations of Latin American origin. We will set the stage by defining the terms Hispanic, Latino, and Latin American, explaining the challenges identifying Hispanics/Latinos in the scientific literature and databases, describing the epidemiology of diabetes-including type 2 DM and gestational diabetes mellitus (GDM)-and cardiovascular risk factors in Hispanics/Latinos in the US and Latin America, and discussing trends, and commonalities and differences across studies and populations, including methodology to ascertain diabetes. We will discuss studies on mechanisms of disease, and research on prevention of type 2 DM in Hispanics/Latinos, including women with GDM, youth and adults; and finalize with a discussion on lessons learned and opportunities to enhance research, and, consequently, clinical care oriented toward preventing type 2 DM in Hispanics/Latinos in the US and Latin America.

Targeting skeletal muscle mitochondria to prevent type 2 diabetes in youth

The prevalence of type 2 diabetes (T2D) has increased dramatically over the past two decades, not only among adults but also among adolescents. T2D is a systemic disorder affecting every organ system and is especially damaging to the cardiovascular system, predisposing individuals to severe cardiac and vascular complications. The precise mechanisms that cause T2D are an area of active research. Most current theories suggest that the process begins with peripheral insulin resistance that precedes failure of the pancreatic β-cells to secrete sufficient insulin to maintain normoglycemia. A growing body of literature has highlighted multiple aspects of mitochondrial function, including oxidative phosphorylation, lipid homeostasis, and mitochondrial quality control in the regulation of peripheral insulin sensitivity. Whether the cellular mechanisms of insulin resistance in adults are comparable to that in adolescents remains unclear. This review will summarize both clinical and basic studies that shed light on how alterations in skeletal muscle mitochondrial function contribute to whole body insulin resistance and will discuss the evidence supporting high-intensity exercise training as a therapy to circumvent skeletal muscle mitochondrial dysfunction to restore insulin sensitivity in both adults and adolescents.

Childhood obesity and insulin resistance: how should it be managed?

OPINION STATEMENT

Concomitant with the rise in global pediatric obesity in the past decades, there has been a significant increase in the number of children and adolescents with clinical signs of insulin resistance. Given insulin resistance is the important link between obesity and the associated metabolic abnormalities and cardiovascular risk, clinicians should be aware of high risk groups and treatment options. As there is no universally accepted biochemical definition of insulin resistance in children and adolescents, identification and diagnosis of insulin resistance usually relies on clinical features such as acanthosis nigricans, polycystic ovary syndrome, hypertension, dyslipidemia, and nonalcoholic fatty liver disease. Treatment for reducing insulin resistance and other obesity-associated comorbidities should focus on changes in health behaviors to achieve effective weight management. Lifestyle interventions incorporating dietary change, increased physical activity, and decreased sedentary behaviors, with the involvement of family and adoption of a developmentally appropriate approach, should be used as the first line treatment. Current evidence suggests that the primary objective of dietary interventions should be to reduce total energy intake and a combination of aerobic and resistance training should be encouraged. Metformin can be used in conjunction with a lifestyle intervention program in obese adolescents with clinical insulin resistance to achieve weight loss and to improve insulin sensitivity. Ongoing evaluation and research are required to explore optimal protocol and long-term effectiveness of lifestyle interventions, as well as to determine whether the improvements in insulin sensitivity induced by lifestyle interventions and weight loss will lead to a clinical benefit including reduced cardiovascular morbidity and mortality.

Physical activity and markers of insulin resistance in adolescents: role of cardiorespiratory fitness levels--the HELENA study

OBJECTIVE

To analyze the association between objectively assessed physical activity (PA) and markers of insulin resistance (IR) in European adolescents and to examine whether the association of objectively assessed PA and markers of IR is modified by cardiorespiratory fitness (CRF).

METHODS

A cross-sectional study at school setting was conducted in 1053 (554 girls) adolescents (12.5-17.5 yr). Weight, height, waist circumference, total body fat, PA (accelerometry), and CRF (20-m shuttle run test) were measured. Fasting insulin and glucose concentrations were measured, and homeostasis model assessment as well as quantitative insulin sensitivity check index were computed.

RESULTS

In males, vigorous PA (VPA) was negatively associated with markers of IR after adjusting for confounders including waist circumference (all p < 0.05). In females, moderate PA, moderate to vigorous PA, and average PA were negatively associated with markers of IR after adjusting for confounders (all p < 0.05). Moreover, when the sample was segmented by CRF levels all the PA intensities were significantly associated with the markers of IR in females with low CRF but not in those with middle-high CRF after adjusting for confounders.

CONCLUSIONS

The findings suggest that PA is negatively associated with markers of IR after adjusting for confounders including total and central body fat in both sexes, but this relationship is modified by the CRF levels being especially important in those females with low CRF. Preventive strategies should focus not only on increasing the volume of PA but also on enhancing CRF through VPA.

Physical activity is related to insulin sensitivity in children and adolescents, independent of adiposity: a review of the literature

In adults, there is evidence that physical activity effectively improves insulin sensitivity regardless of adiposity. Whether this is also the case in children and adolescents is less clear. Clarifying this matter may help to identify the best outcomes to target in exercise programs for these age groups, where changes in adiposity may not always be desirable or realistic. A review of the literature was conducted on studies that examined the relationships of physical activity, cardiorespiratory fitness and strength with insulin sensitivity independent of adiposity in children and adolescents. Experimental (intervention) and correlational (longitudinal and cross-sectional) studies on participants ages 18 years and younger were identified. A total of 42 studies were included in this review. Sample sizes in the studies ranged from 14 to 4955 participants, with individual ages ranging from 5 to 19 years. A significant relationship with insulin sensitivity existed in 78% of studies on physical activity, 69% of studies on cardiorespiratory fitness and 66% of studies on strength. In studies that examined both physical activity and cardiorespiratory fitness concurrently, evidence suggests that they are both correlated with insulin sensitivity independent of adiposity, especially when physical activity is at higher intensities. However, the strength of this relationship might be influenced by study design, measurement techniques and participant characteristics. This is the first review of its type to take research design into account and to examine study outcomes according to participant ethnicity, gender, age, pubertal status and weight status.

[Physical activity among aboriginals in Canada]

This paper summarizes available information on patterns of physical activity, their determinants and consequences, and the results of various interventions designed to increase the physical activity of Aboriginal peoples in Canada and the United States. There is a paucity of national data on this issue for Aboriginal peoples. The most recent data, from the First Nations Regional Longitudinal Health Survey of 2002-2003, indicate that 21% of adults (27% of men, 15% of women) were engaging in at least 30 min of moderate to vigorous physical activity on 4 d/week or more. The present paper highlights the unique challenges this group faces, underlining the need to integrate collective knowledge regarding how much physical activity is required for Aboriginal Canadians, and how this activity should be accomplished, to promote and maintain health. Efforts are currently underway to tailor Canada's physical activity guide for First Nations, Inuit, and Métis. Future research among Aboriginal groups should examine the minimal and optimal levels of physical activity required to achieve health benefits.

Insulin sensitivity, VO2max and body composition in severely obese Swedish children and adolescents

AIM

The aim of this study was to identify relationships between insulin sensitivity (SI), cardiorespiratory fitness and body composition in severely obese Swedish children and adolescents.

METHODS

Two hundred and twenty-eight obese children (119 girls, 8-16 years, body mass index (BMI) 23.2-57.0 kg/m(2)) performed a frequently sampled intravenous glucose tolerance test (FSIVGTT), a submaximal bicycle ergometry test and a dual-energy X-ray absorptiometry (DEXA).

RESULTS

Mean SI (SD) was 0.38 (0.32) (x10(-5)/min/pM). SI correlated positively with relative body mass (BM) VO(2)max (r = 0.42) (p < 0.001), relative fat-free mass (FFM) VO(2)max (r = 0.36) (p < 0.001) and negatively with body mass index standard deviation score (BMI SDS) (r =-0.22) (p = 0.001). SI did not correlate with percent body fat (r =-0.01) and absolute VO(2)max (r = 0.01). In multiple regression analyses with SI as dependent variable, VO(2)max and body composition, together with gender, age and Tanner stage, explained 20-26% of the variance.

CONCLUSION

Relative (BM) VO(2)max and relative (FFM) VO(2)max were stronger predictors of SI than percent body fat in severely obese children and adolescents. The study confirms that cardiorespiratory fitness is of importance for the metabolic syndrome in the studied population. Efforts to improve SI should include physical activity targeting cardiorespiratory fitness also in severely obese children and adolescents.

Acquired obesity and poor physical fitness impair expression of genes of mitochondrial oxidative phosphorylation in monozygotic twins discordant for obesity

Defects in expression of genes of oxidative phosphorylation in mitochondria have been suggested to be a key pathophysiological feature in familial insulin resistance. We examined whether such defects can arise from lifestyle-related factors alone. Fourteen obesity-discordant (BMI difference 5.2 +/- 1.8 kg/m(2)) and 10 concordant (1.0 +/- 0.7 kg/m(2)) monozygotic (MZ) twin pairs aged 24-27 yr were identified among 658 MZ pairs in the population-based FinnTwin16 study. Whole body insulin sensitivity was measured using the euglycemic hyperinsulinemic clamp technique. Transcript profiles of mitochondrial genes were compared using microarray data of fat biopsies from discordant twins. Body composition of twins was determined using DEXA and maximal oxygen uptake (Vo(2max)) and working capacity (W(max)) using a bicycle ergometer exercise test with gas exchange analysis. The obese cotwins had lower insulin sensitivity than their nonobese counterparts (M value 6.1 +/- 2.0 vs. 9.2 +/- 3.2 mg x kg LBM(-1) x min(-1), P < 0.01). Transcript levels of genes involved in the oxidative phosphorylation pathway (GO:0006119) in adipose tissue were lower (P < 0.05) in the obese compared with the nonobese cotwins. The obese cotwins were also less fit, as measured by Vo(2max) (50.6 +/- 6.5 vs. 54.2 +/- 6.4 ml x kg LBM(-1) x min(-1), for obese vs. nonobese, P < 0.05), W(max) (3.9 +/- 0.5 vs. 4.4 +/- 0.7 W/kg LBM, P < 0.01) and also less active, by the Baecke leisure time physical activity index (2.8 +/- 0.5 vs. 3.3 +/- 0.6, P < 0.01). This implies that acquired poor physical fitness is associated with defective expression of the oxidative pathway components in adipose tissue mitochondria.

Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children

OBJECTIVE

We examined the independent relationships between objectively measured physical activity and insulin resistance in Portuguese children.

RESEARCH DESIGN AND METHODS

This is a school-based, cross-sectional study in 147 randomly selected girls (aged 9.8 +/- 0.3 years; 27.8 +/- 9.3% body fat) and 161 boys (aged 9.8 +/- 0.3 years; 22.0 +/- 9.2% body fat). Physical activity was assessed by the Actigraph accelerometer for 4 days and summarized as time spent sedentary (accelerometer counts <500/min), in light-intensity (accelerometer counts 500-2,000/min), and in moderate- and vigorous-intensity activity (accelerometer counts >2,001/min). We measured total and central fat mass by dual-energy X-ray absorptiometry. Insulin resistance was expressed as the homeostasis model assessment score.

RESULTS

Time (min/day) spent sedentary was significantly and positively associated with insulin resistance (beta-coefficient = 0.001 [95% CI 0.0002-0.002]; P = 0.013). Time spent in moderate- and vigorous-intensity physical activity (-0.002 [-0.003 to -0.001]; P = 0.0009) and overall physical activity (-0.001 [-0.008 to 0.003]; P < 0.0001) were significantly and inversely associated with insulin resistance. All associations remained statistically significant, although they were attenuated after further adjustments for sex, birth weight, sexual maturity, and total or central fat mass (P < 0.03).

CONCLUSIONS

Physical activity is associated with insulin resistance independent of total and central fat mass in children. Our results emphasize the importance of decreasing sedentary behavior and increasing time spent in moderate- and vigorous-intensity activity in children, which may have beneficial effects on metabolic risk factors regardless of the degree of adiposity.

Associations between physical activity, body fat, and insulin resistance (homeostasis model assessment) in adolescents: the European Youth Heart Study

BACKGROUND

More and better data are needed to understand the action of physical activity (PA) on insulin resistance and the concomitant relation with body fat in adolescence.

OBJECTIVE

We examined the relation between total PA and intensity levels with insulin resistance under special consideration of waist circumference and skinfold thickness.

DESIGN

This was a cross-sectional study of 613 adolescents (352 girls, 261 boys) with a mean (+/-SD) age of 15.5 +/- 0.5 y from Sweden and Estonia. Total, low, moderate, and vigorous PA was measured by accelerometry. Body fat estimators included waist circumference and the sum of 5 skinfold thicknesses. Fasting insulin and glucose were measured, and insulin resistance was calculated according to the homeostasis model assessment (HOMA). Linear regression analysis and analysis of covariance were used to determine the association between PA and insulin resistance while considering body fat. All estimates were adjusted for sex, country, pubertal status, and indicators of body fat when applicable.

RESULTS

Total, moderate, and vigorous PA were inversely correlated with HOMA. Body fat estimators were positively correlated with HOMA. Significant contrasts in HOMA concentrations were seen when comparing the lower 2 tertiles with the upper tertile of PA indicators. Repeating the analysis with body fat estimators showed significant contrasts in HOMA concentrations when comparing the lower tertiles with the upper tertile.

CONCLUSION

In view of an increase in obesity in young people, the results accentuate the role of PA in sustaining metabolic balance in adolescence and the potential benefit of an increase of time spent at higher PA levels for youth with relatively elevated amounts of body fat.

Physical activity of Aboriginal people in CanadaThis article is part of a supplement entitled Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines co-published by Applied Physiology, Nutrition, and Metabolism and the Canadian Journal of Public Health. It may be cited as Appl. Physiol. Nutr. Metab. 32(Suppl. 2E) or as Can. J. Public Health 98(Suppl. 2)

This paper summarizes available information on patterns of physical activity, their determinants and consequences, and the results of various interventions designed to increase the physical activity of Aboriginal peoples in Canada and the United States. There is a paucity of national data on this issue for Aboriginal peoples. The most recent data, from the First Nations Regional Longitudinal Health Survey of 2002–2003, indicate that 21% of adults (27% of men, 15% of women) were engaging in at least 30 min of moderate to vigorous physical activity on 4 d/week or more. The present paper highlights the unique challenges this group faces, underlining the need to integrate collective knowledge regarding how much physical activity is required for Aboriginal Canadians, and how this activity should be accomplished, to promote and maintain health. Efforts are currently underway to tailor Canada’s physical activity guide for First Nations, Inuit, and Métis. Future research among Aboriginal groups should examine the minimal and optimal levels of physical activity required to achieve health benefits.

Markers of insulin resistance are associated with fatness and fitness in school-aged children: the European Youth Heart Study

AIMS/HYPOTHESIS

Our aim was to examine the association between markers of insulin resistance and: (1) body fat and waist circumference, taking into account cardiorespiratory fitness in school-aged children; and (2) cardiorespiratory fitness at differing levels of body fat and waist circumference.

SUBJECTS AND METHODS

This was a cross-sectional study of 873 children aged 9.6 +/- 0.4 years from Estonia and Sweden. Weight, height and waist circumference were measured. Body fat was expressed as the sum of five skinfold thicknesses. Cardiorespiratory fitness was estimated by a maximal cycle-ergometer test. The studied markers of insulin resistance were fasting insulin and glucose, and homeostasis model assessment (HOMA).

RESULTS

HOMA and fasting insulin were positively associated with body fat and waist circumference after adjusting for cardiorespiratory fitness, age, pubertal status and study location. HOMA and fasting insulin were negatively associated with cardiorespiratory fitness in children in the third (highest) tertile of body fat and waist circumference after controlling for sex, age, pubertal status and study location. Fasting glucose was negatively associated with cardiorespiratory fitness in children in the third (highest) tertile of waist circumference, but it was not associated when body fat was taken into account.

CONCLUSIONS/INTERPRETATION

In school-aged children, HOMA and fasting insulin are significantly associated with body fat and waist circumference. In addition, cardiorespiratory fitness explains a significant proportion of the HOMA and fasting insulin variance in those children with high levels of body fat and waist circumference. The findings suggest that the deleterious consequences ascribed to high fatness could be counteracted by having high levels of cardiorespiratory fitness.

Age, sex, and ethnic variations in serum insulin concentrations among U.S. youth: findings from the National Health and Nutrition Examination Survey 1999-2002

OBJECTIVE

Distributions of serum concentrations of insulin among adolescents and young adults are poorly understood in the U.S. The objective of this study was to describe the distribution of serum insulin across demographic characteristics of U.S. adolescents and young adults.

RESEARCH DESIGN AND METHODS

A total of 1,791 male and female subjects aged 12-19 years who participated in the National Health and Nutrition Examination Surveys for 1999-2002 were included in the analyses.

RESULTS

Among male participants, serum concentrations of insulin increased from age 12 to 14 years before decreasing. Among female participants, concentrations were highest at age 13 years before decreasing steadily through age 19 years. Among participants aged 12-17 years but not those aged 18-19 years, females had higher mean log-transformed concentrations than males (P, Wald, F = 0.038 and 0.125, respectively) after adjusting for age and ethnicity. After adjusting for age and BMI percentile, mean log-transformed concentrations were higher in African-American females aged 12-17 years than in white or Mexican-American participants. No significant ethnic differences were found among female participants aged 18-19 years or male participants aged 12-19 years. Concentrations of insulin increased strongly with increasing levels of BMI.

CONCLUSIONS

These results provide detailed information about serum concentrations of insulin in a representative sample of U.S. adolescents and young adults and may be useful to monitor future trends of this risk factor for diabetes and cardiovascular disease.

Haemoglobin A1c is not a surrogate for glucose and insulin measures for investigating the early life and childhood determinants of insulin resistance and Type 2 diabetes in healthy children. An analysis from the Avon Longitudinal Study of Parents and Children (ALSPAC)

AIMS

Research into early life and childhood determinants of insulin resistance and Type 2 diabetes are complicated by requirements for fasting blood samples and glucose tolerance tests. We investigated haemoglobin A(1c) (HbA(1c)), a marker of glycaemia measured in non-fasting blood, as an alternative.

METHODS

HbA(1c) was measured in 1645 children aged 9-11 years without diabetes from the Avon Longitudinal Study of Parents and Children. Thirty-nine children had two HbA(1c) measurements. Data on parental, child and potential confounding factors were collected prospectively from questionnaires, medical records and direct examination. Data from a shortened 30-min oral glucose tolerance test were available for 431 children at age 8 years. Body composition was measured by dual-energy X-ray absorptiometry.

RESULTS

Mean (sd) HbA(1c) was 4.91(0.29)%. HbA(1c) increased with age and was higher in boys compared with girls, non-white compared with white children, and in children with anaemia. Mean difference between repeated HbA(1c) measurements was 0.01%. HbA(1c) was weakly positively associated with fasting glucose (beta = 0.066%/mmol/l, P = 0.05), but was not associated with 30-min glucose, fasting or 30-min insulin, or homeostasis model assessment-insulin resistance. HbA(1c) was weakly inversely associated with weight sd score (beta =-0.02%/unit, P = 0.004), body mass index sd score (beta = -0.02%/unit, P = 0.002), and total body fat (beta = -0.003%/kg, P = 0.06) and lean mass (beta = -0.011%/kg, P = 0.01), but was not associated with birthweight or breastfeeding.

CONCLUSIONS

HbA(1c) is not a good marker of fasting or post-load glucose and insulin measures in healthy children, and is not a viable alternative to these measures for investigating the determinants of insulin resistance and Type 2 diabetes in children.

The nutrition transition in American Indians

The purpose of this article was to examine whether a nutritional transition has occurred among American Indians (AI) by evaluating related articles and government health statistics. Findings indicate that although the primary health risk for the AI population around 1970 was undernutrition, now there is an obesity epidemic among all age groups that is associated with a loss of traditional food practices and reduced physical activity. Deaths caused by cardiovascular disease, diabetes mellitus, and cancer have outpaced death from infectious disease. With abundant high-energy foods and limited physical activity, the acculturated environment has resulted in obesity and increased mortality from chronic diseases. To improve AI health and survival, the obesity epidemic must be approached in a concerted, culturally appropriate manner with encouragement of traditional foods and safe opportunities for physical activity.

Cardiovascular fitness and physical activity in children with and without impaired glucose tolerance

OBJECTIVE

To examine differences in cardiovascular fitness (VO(2max)) and physical activity levels in overweight Hispanic children with normal glucose tolerance (NGT) vs impaired glucose tolerance (IGT).

PARTICIPANTS

A total of 173 overweight (BMI percentile 97.0 +/- 3.1) Hispanic children ages 8-13 years with a family history of type 2 diabetes.

METHODS

VO(2max) was measured via a maximal effort treadmill test and open circuit spirometry. Physical activity was determined by questionnaire. Glucose tolerance was established by a 2-h oral glucose challenge (1.75 g of glucose/kg body weight). IGT was defined from an oral glucose tolerance test as a 2-h plasma glucose level > or =140 and <200 mg/dl.

RESULTS

IGT was detected in 46 of the 173 participants (approximately 27%); no cases of type 2 diabetes were identified. No significant differences were found between youth with NGT and those with IGT in absolute VO(2max) (2.2 +/- 0.6 vs 2.1 +/- 0.5 l/min), VO(2max) adjusted for gender, age, and body composition (2.2 +/- 0.2 vs 2.1 +/- 0.2 l/min), or recreational physical activity levels (8.7 +/- 8.2 vs 6.9 +/- 6.2 h/week).

CONCLUSION

Overweight Hispanic youth with IGT exhibit similar levels of VO(2max) and physical activity compared to their NGT counterparts. Longitudinal analyses are necessary to determine whether fitness/activity measures contribute significantly to diabetes risk over time in this group.

Physical activity, cardiovascular fitness, and insulin sensitivity among U.S. adolescents: the National Health and Nutrition Examination Survey, 1999-2002

OBJECTIVE

The purpose of this study was to examine the association of physical activity and cardiovascular fitness (CVF) with insulin sensitivity in a nationally representative sample of U.S. youth.

RESEARCH DESIGN AND METHODS

The study included 1,783 U.S. adolescents (11% Mexican American, 14% non-Hispanic black, 63% non-Hispanic white, and 12% other) aged 12-19 years who were examined in the 1999-2002 National Health and Nutrition Examination Survey. Physical activity was assessed by questionnaire and expressed in units of MET hours per week. Predicted maximal oxygen uptake (Vo(2max), expressed in milliliters per kilogram of body weight per minute), a measure of CVF, was determined by a submaximal multistage treadmill test. Insulin sensitivity was defined by the Quantitative Insulin Sensitivity Check Index.

RESULTS

Boys were more likely than girls to be highly active (>or=30 MET h/week; 51 vs. 37%, P < 0.001) and had higher levels of CVF (mean Vo(2max) 47 vs. 39 ml x kg(-1) x min(-1), P < 0.001). Sex-specific multiple regression models controlled for age, race/ethnicity, and BMI showed that in boys, high levels of physical activity and high levels of CVF were significantly and positively associated with insulin sensitivity (beta = 0.84, P < 0.001 and beta = 0.82, P = 0.01, respectively). Among girls, insulin sensitivity was not significantly associated with physical activity or with CVF but was inversely and significantly associated with BMI.

CONCLUSIONS

Increasing physical activity and CVF may have an independent effect of improving insulin sensitivity among boys. For girls, the primary role of physical activity may be in weight maintenance.

Patterns of physical activity determined by heart rate monitoring among diabetic children

BACKGROUND

Children with type 1 diabetes should be encouraged to participate in physical activity because exercise can benefit insulin sensitivity and improve known risk factors for atherosclerosis.

METHODS

Physical activity patterns of 127 children and adolescents with stable type 1 diabetes were investigated by 24 hour continuous heart rate monitoring. The percentage of heart rate reserve was used to measure the amounts of physical activity at different intensities. The results were compared with normative data.

RESULTS

Diabetic preschoolchildren accumulated 192.7 (78.1), 39.1 (24.3), and 21.3 (9.4) minutes/day (mean (SD)) of light, moderate, and vigorous physical activity, respectively. At the same activity levels, diabetic schoolchildren accumulated 168.9 (76.7), 37.9 (15.9), and 19.0 (14.8) minutes/day, and diabetic teenagers accumulated 166.3 (67.5), 45.6 (26.9), and 25.2 (15.3) minutes/day. Diabetic schoolchildren were significantly more active than healthy peers when considering moderate activity; diabetic teenagers were significantly more active when considering moderate and vigorous activity. There was a negative correlation between the most recent glycated haemoglobin and the time spent in light activities in schoolchildren, and a negative correlation between mean glycated haemoglobin for one year and time spent in light and moderate activities in schoolchildren.

CONCLUSION

The majority of our diabetic patients meet the classical paediatric guidelines for physical activity and compare favourably with their healthy peers.

Physical activity and energy intake in adolescent girls with Type 1 diabetes

AIMS

Girls with Type 1 diabetes often gain excessive weight during puberty. The aims of this study were to compare objectively assessed physical activity and energy intake in girls with Type 1 diabetes with those in healthy age-matched controls.

METHODS

This prospective cohort study comprised 26 girls with Type 1 diabetes and 49 control girls. The mean age of the diabetic girls was 15.7 +/- 2.1 years and that of the control girls 15.8 +/- 2.1 years. In the diabetic group, mean haemoglobin A1c was 7.6 +/- 1.4% and daily insulin dosage was 1.1 +/- 0.3 U/kg. Physical activity was measured during 7 consecutive days with a uniaxial accelerometer, and energy intake was assessed concurrently with a 7-day food diary.

RESULTS

There was a tendency towards lower total amount of physical activity in the diabetes group but the difference between the study groups did not reach statistical significance (Diabetes: 464 +/- 123 counts/min/day;

CONTROLS

523 +/- 138 counts/min/day; P = 0.06). No difference was found between the groups regarding total energy intake (Diabetes: 8.5 +/- 1.8 MJ/day;

CONTROLS

8.4 +/- 2.6 MJ/day). The carbohydrate intake was lower and the protein and fibre intakes were higher in girls with diabetes. No association was observed between physical activity, energy intake and HbA1c.

CONCLUSIONS

In this prospective cohort study, we found a tendency towards lower physical activity but no differences in energy intake between girls with Type 1 diabetes and age-matched controls. Larger studies are needed to further explore the importance of the total amount of physical activity for excessive weight gain in adolescent girls with Type 1 diabetes.

Impact of the Bienestar school-based diabetes mellitus prevention program on fasting capillary glucose levels: a randomized controlled trial

OBJECTIVE

To evaluate the impact of a school-based diabetes mellitus prevention program on low-income fourth-grade Mexican American children.

DESIGN

A randomized controlled trial with 13 intervention and 14 control schools.

SETTING

Elementary schools in inner-city neighborhoods in San Antonio, Tex.

PARTICIPANTS

Eighty percent of participants were Mexican American and 94% were from economically disadvantaged households. Baseline and follow-up measures were collected from 1419 (713 intervention and 706 control) and 1221 (619 intervention and 602 control) fourth-grade children, respectively.

INTERVENTION

The Bienestar Health Program consists of a health class and physical education curriculum, a family program, a school cafeteria program, and an after-school health club. The objectives are to decrease dietary saturated fat intake, increase dietary fiber intake, and increase physical activity.

MAIN OUTCOME MEASURES

The primary end point was fasting capillary glucose level, and the secondary end points were percentage of body fat, physical fitness level, dietary fiber intake, and dietary saturated fat intake. Fasting capillary glucose level, bioelectric impedance, modified Harvard step test, three 24-hour dietary recalls, weight, and height were collected at baseline and 8 months later.

RESULTS

Children in the intervention arm attended an average of 32 Bienestar sessions. Mean fasting capillary glucose levels decreased in intervention schools and increased in control schools after adjusting for covariates (-2.24 mg/dL [0.12 mmol/L]; 95% confidence interval, -6.53 to 2.05 [-0.36 to 0.11 mmol/L]; P =.03). Fitness scores (P =.04) and dietary fiber intake (P =.009) significantly increased in intervention children and decreased in control children. Percentage of body fat (P =.56) and dietary saturated fat intake (P =.52) did not differ significantly between intervention and control children.

CONCLUSION

This intervention showed some positive results, but additional research is needed to examine long-term benefits, translation, and cost-effectiveness.