Does beta cell dysfunction or insulin resistance play a role in the development of adiposity? [abstract]

OBJECTIVE: To test the hypothesis that pre-existing beta cell function (BCF) and insulin resistance (IR) are related to the development of adiposity. METHOD: A sample of 493 subjects (mean age 47ñ18 yrs; 55 percent women) was selected from the Spanish Town Survey. Base-line anthropometry, blood pressure, lipid profile, oral glucose tolerance test and fasting insulin levels were done. Anthropometry was repeated 4.5 years later in 319 subjects. Baseline IR and BCF were computed using the method of homeostatic model assessment. Cross-sectional and prospective associations between measures of adiposity (body mass index, waist-hip ratio) and explanatory variables (age, gender, IR, BCF, lipids, blood pressure, glycaemia) were assessed using correlation and multiple linear regression and analyses. RESULTS: Baseline body mass index (BMI) and waist:hip ratio (WHR), folow-up BMI and WHR, change in weight and change in BMI, but not change in WHR, were correlated with IR (r=-0.120; p<0.001). BCF was correlated only with baseline WHR (r=-0.21; p<0.001). In multiple regression analyses, gender, HDL-C, LDL-C, BCF and IR were associated with baseline BMI regardless of glycaemic state. Baseline WHR was associated with the same variables and triglycerides (TG), but the association with the BCF and TG lost significance in subjects with normoglycaemia. Follow-up BMI was associated with age, IR, HDL-C and LDL-C, but not after adjustment for baseline BMI. Follow-up WHR was associated with gender, TG and HDL-C. After adjustment for baseline WHR or BMI, only gender and lipids remained significant. IR, TG and baseline BMI were associated with change in weight. Change in BMI was significantly correlated with IR, but not after adjustment for baseline BMI. Change in WHR was associated with baseline WHR and gender. CONCLUSIONS: BCF and IR are independently associated with current adiposity. IR, but not BCF, significantly explains some of the variance of future adiposity. However, this effect is ameliorated if baseline adiposity is considered. (AU)

Obesity in a cohort of black Jamaican children as estimated by body mass index (BMI) and other indices of adiposity [abstract]

OBJECTIVE: To examine the relationships of Body Mass Index (BMI) to obesity indices derived from anthropometry and to determine tracking of obesity between late childhood and early adolescence. We also compared identification of over-weight children using the International Obesity Task Force (IOTF) BMI cut points with skinfolds. METHODS: Three hundred and six children were examined at 7-8 years and at 11-12 years. Triceps (TSF) and subscapular (SSF) skin folds, height, and weight were measured. The sum of the skinfolds (sum SF), BMI, and fat mass (FM) were calculated. Pubertal stage was assessed at 11-12 years. RESULTS: At age 7-8 years, 11 children were overweight compared with 29 at 11-12 years. BMI was better correlated with the other indices of adiposity in girls than in boys and in the older age group than in the 7-8-year-olds. In regression analysis, BMI predicted FM best and explained 52 percent and 61 percent of the variance in FM among boys and girls at 7-8 years. Using the IOTF cut points, BMI had low sensitivity to identify children >85th percentile of the NHANES references for SSF. The sensitivity for those assessed by TSF and sum SF was higher but between 14 percent and 30 percent of the children were misclassified. The specificity of BMI was high. CONCLUSION: Adiposity increased between mid-childhood and early adolescence but the children remained realtively lean. Girls were fatter than boys, reflecting adult obesity patterns. Children identified as overweight by the IOTF BMI cut points are likley to have high body fatness. However, the concern would be that the BMI cut points may not identify many children with high body fatness. (AU)