Black and white adolescents who engaged in relatively large amounts of free-living vigorous exercise were likely to be relatively fit and lean.

OBJECTIVE: To determine the effect of exercise training (ET) on components of the insulin resistance syndrome (IRS) in obese children. DESIGN: Randomized, modi®ed cross-over study, with subjects assigned to one of two conditions: (1) 4 months of ET followed by 4 months of no-ET; or (2) 4 months of no-ET followed by 4 months of ET. Measurements were made at three time points: 0, 4 and 8 months. SUBJECTS: 79 obese, but otherwise healthy children (age: 7 ± 11 y, percent fat (%fat) 27 ± 61%). MEASUREMENTS: Plasma lipid and lipoprotein concentrations, plasma insulin and glucose concentrations; %fat; submaximal heart rate (HR) as an index of ®tness. EXERCISE TRAINING: ET was offered 5 daweek 40 minad. For the 73 children who completed 4 months of ET, the mean attendance was 80% (that is, 4 daweek) and the average HR during ET was 157 bpm. RESULTS: Signi®cant (P`0.05) group x time interactions were found for plasma triglyceride (TG) and insulin concentrations and %fat. The average change for both groups, from just before ET to just after the 4 month ET was À0.24 mmol Á l À1 for TG, À25.4 pmol Á l À1 for insulin and À1.6 units for %fat. When Group 1 ceased ET, over the following 4 month period the average change for insulin was 26.6 pmol Á l À1 and for %fat 1.3 units. CONCLUSION: Some components (plasma TG, insulin, %fat) of the IRS are improved as a result of 4 months of ET in obese children. However, the bene®ts of ET are lost when obese children become less active.

Black youths had a more favorable HRV profile than white youths. After controlling for age, race, and sex, more favorable HRV profiles were associated with more MVPA, better CVF, and less visceral and subcutaneous adiposity. The deleterious impact of higher adiposity was greater in blacks, especially females, than in whites. Enhancement of cardiac autonomic modulation may be a pathway through which physical activity, fitness, and leanness contribute to cardiovascular health early in life.

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of visceral adiposity to cardiovascular disease risk factors in black and white teens. Obesity. 2007;15:1029 -1035. Objective: We tested the hypothesis that visceral adiposity, compared with general adiposity, would explain more of the variance in cardiovascular disease (CVD) risk factors. Research Method and Procedures: Subjects were 464 adolescents (238 black and 205 girls). Adiposity measures included visceral adipose tissue (VAT; magnetic resonance imaging), percent body fat (%BF; DXA), BMI, and waist girth (anthropometry). CVD risk factors were fasting insulin, fibrinogen, total to high-density lipoprotein-cholesterol ratio, triglycerides (TGs), systolic blood pressure, and left ventricular mass indexed to height 2.7 . Results: After adjustment for age, race, and sex, all adiposity indices explained significant proportions of the variance in all of the CVD risk factors; %BF tended to explain more variance than VAT. Regression models that included both %BF and VAT found that both indices explained independent proportions of the variance only for total to highdensity lipoprotein-cholesterol ratio. For TGs, the model that included both %BF and VAT found that only VAT was significant. For systolic blood pressure and left ventricular mass indexed to height 2.7 , anthropometric measures explained more of the variance than VAT and %BF. Discussion: The hypothesis that visceral adiposity would explain more variance in CVD risk than general adiposity was not supported in this relatively large sample of black and white adolescents. Only for TGs did it seem that VAT was more influential than %BF. Perhaps the deleterious effect of visceral adiposity becomes greater later in life as it increases in proportion to general adiposity.

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Background: Excess body fat accumulation may begin in youth and is linked with increased risk of cardiovascular disease. Examination of physical activity (PA) and diet behaviours predictive of adiposity may help target efforts to reduce chronic disease risk. Objective: We hypothesized that energy intake (EI) from fat, vigorous PA (VPA), and their interaction would predict body fat percentage (%BF) and visceral adipose tissue (VAT) in youth and that sedentary behaviours and intake of dairy, fruit, vegetable and whole grain foods would be related to adiposity. Design: A cross-sectional, observational study of reported PA and diet behaviours and objective adiposity measures. Subjects: Six-hundred sixty-one healthy black and white adolescents aged 14-18 years. Measurements: Diet by 24-h recalls using Nutrition Data Systems for Research (Minneapolis, MN, USA), VPA by previous day physical activity recalls (PAR), and %BF with dual-energy X-ray absorptiometry. VAT by magnetic resonance imaging for 434 subjects. Results: Reported EI and VPA were positively correlated with each other and were negative predictors of %BF. Time spent watching television or movies and %EI from protein were positive predictors of %BF. Adjusted for EI, none of the independent variables predictive of %BF retained their significance. %BF and VAT were highly correlated (r ¼ 0.73, Po0.0001). EI was the sole and negative predictor of VAT. Conclusions: Higher energy 'throughput', not energy restriction, characterize leaner youths. Youths should be advised to engage in VPA so that they can eat sufficient calories to obtain the nutrients required for optimal health while remaining lean.

Most internal medicine resident physicians may not be adequate role models for promoting exercise adherence. Confidence in the knowledge of current guidelines, personal physical activity enjoyment, and perceived success and self-efficacy in engaging in regular physical activity may be useful targets for enhancing resident physician physical activity counseling for their patients.