These findings suggest that the decision rules employed to process accelerometer data have a significant impact on important outcome variables. Until guidelines are developed, it will remain difficult to compare findings across studies.

Objective To evaluate a 12-session home and community-based health promotion/obesity prevention program (Challenge!) on changes in BMI, body composition, physical activity (PA), and diet. Methods 235 African-American adolescents (11–16 yrs, 38% overweight/obese) were recruited from low-income urban communities. Baseline measures included weight, height, body composition (dual-energy x-ray absorptiometry (DEXA) and bioelectrical impedance), physical activity (PA) (accelerometry), and diet (food frequency). PA was measured by time in play-equivalent physical activity (PEPA≥1800 activity counts/min). Participants were randomized into a home- and community-based health promotion/obesity prevention controlled trial, anchored in social cognitive theory and involving motivational interviewing techniques, and delivered by college-enrolled, African-American mentors. Control adolescents did not receive the intervention or a mentor. Post-intervention (10 mos) and delayed follow-up (24 mos) evaluations were conducted. Longitudinal analyses using random mixed effects models and generalized estimating equations (GEE) examined direct and moderated effects of time, gender, and baseline BMI category on changes at both follow-ups. Results Retention was 76% (178/235) over 2 years; overweight/obese status declined 5.3% among intervention adolescents and increased 11.3% among control adolescents (χ2=5.8, p=0.02, GEE). Among males, but not females, fat free mass was significantly higher among intervention members at both follow-up evaluations. PA effects were moderated by baseline BMI category; among adolescents ≥ 85th percentile, control adolescents averaged 25.5 min less daily activity than intervention adolescents (p=0.018) at the 10-mo, but not the 24-mo follow-up. Intervention adolescents declined significantly more in snack and dessert consumption than control adolescents (p=0.045). Conclusion A 12-session, home-and community-based intervention, based on social cognitive theory and delivered by college-enrolled mentors, had sustained effects over 24 months in preventing an increase in BMI category, in enhancing fat free mass among males, and in reducing snack and dessert intake. The intervention prevented PA declines among the heaviest adolescents, but effects were not sustained.

Extra energy intake is required by healthy pregnant women to support adequate gestational weight gain and increases in BMR, which are not totally offset by reductions in AEE.

The insulin resistance associated with aging may be due, in part, to reduced levels of physical activity in the elderly. We hypothesized that strength training increases insulin action in older individuals. To test this hypothesis, 11 healthy men 50-63 yr old [mean 58 +/- 1 (SE) yr] underwent a two-step hyperinsulinemic-euglycemic glucose clamp with concurrent indirect calorimetry and an oral glucose tolerance test (OGTT) before and after 16 wk of strength training. The training program increased overall strength by 47% (P < 0.001). Fat-free mass (FFM; measured by hydrodensitometry) increased (62.4 +/- 2.1 vs. 63.6 +/- 2.1 kg; P < 0.05) and body fat decreased (27.2 +/- 1.8 vs. 25.6 +/- 1.9%; P < 0.001) with training. Fasting plasma glucose levels and glucose levels during the OGTT were not significantly lower after training. In contrast, fasting plasma insulin levels decreased (85 +/- 25 vs. 55 +/- 10 pmol/l; P < 0.05) and insulin levels decreased (P < 0.05, analysis of variance) during the OGTT. Glucose infusion rates during the hyperinsulinemic-euglycemic glucose clamp increased 24% (13.5 +/- 1.7 vs. 16.7 +/- 2.2 mumol.kg FFM-1.min-1; P < 0.05) during the low (20 mU.m-2.min-1) insulin infusion and increased 22% (55.7 +/- 3.3 vs. 67.7 +/- 3.9 mumol.kg FFM-1.min-1; P < 0.05) during the high (100 mU.m-2.min-1) insulin infusion. These increases were accompanied by a 40% increase (n = 7; P < 0.08) in nonoxidative glucose metabolism during the high insulin infusion. These results demonstrate that strength training increases insulin action and lowers plasma insulin levels in middle-aged and older men.