June 26, 2010 (Orlando, Florida) — Obese boys who engaged in regular aerobic or resistance exercise — without dietary changes — had significant improvements over 3 months in their total body fat, visceral adipose tissue concentrations, and insulin sensitivity than their more sluggish counterparts, according to the results of a small randomized study presented on opening day here at the American Diabetes Association 70th Scientific Sessions.
The results were independent of the type of exercise assigned, and suggest that a moderate increase in activity (180 minutes per week) can help prevent type 2 diabetes mellitus in this high-risk population, said SoJung Lee, PhD, assistant professor of pediatrics at the Children's Hospital of Pittsburgh in Pennsylvania.
Our hypothesis was that "aerobic training would be more beneficial than resistance training for adipose tissue reduction and insulin resistance reduction, but I guess our hypothesis was wrong. We have pilot data [supporting the fact] that during resistance training, the energy expenditure in boys is similar to aerobic training," she said in an interview with Medscape Diabetes & Endocrinology.
To determine the effects of regular exercise without diet on total and abdominal fat and insulin resistance, and to see whether different forms of exercise would produce different outcomes, the investigators designed a randomized study of 26 obese boys, ranging in age from 12 to 18 years. The subjects all had a body mass index in the 95th percentile or higher (mean, 34.9 + 4.6 kg/m2).
The boys were randomly assigned to 1 of 3 groups for the 3-month study: aerobic exercise for 180 minutes/week (n = 9), resistance exercise for 180 minutes/week (n = 11), or no exercise (n = 6; control group). Although boys in the control group were asked to eat a healthy diet, none of the participants were on calorie-restricted diets.
The primary study end points were change from baseline in total and regional body composition measured by whole-body magnetic resonance imaging, and insulin sensitivity measured by a 3-hour hyperinsulinemic-euglycemic clamp.
After 3 months, there were no significant changes in mean body weight in either the aerobic group (–1.0 ± 2.12 kg) or the resistance group (0.3 ± 0.6 kg; P > .10). In contrast, those in the control group, on average, gained more than 4 kg (4.4 ± 0.8 kg; P < .05).
Exercisers had significant gains in cardiorespiratory fitness, compared with controls; the gain in the aerobic group was 37.2% and in the resistance group was 24.9% (P < .05 for each, compared with control group).
Total body fat declined by 9.6% among the aerobic exercisers, and by 4.7% among resistance exercisers (P < .05 for each vs controls). Similarly, visceral adipose tissue concentrations dropped by 12.6% and 13.3%, respectively (P < .50). There were no significant differences in abdominal fat changes between the exercise groups (P > .01).
The insulin sensitivity analysis also showed a benefit in each exercise group, with a 23.3% gain with aerobics and a 35.6% gain with resistance. There were no significant differences in insulin sensitivity between the exercise groups, however (P > .10).
Across all 3 groups, change in abdominal fat correlated significantly with insulin sensitivity (r = –0.45; P < .05).
The study suggests that exercise interventions can work in an at-risk population such as this, particularly when children are given a choice, said Andrew W. Norris, MD, PhD, Assistant professor of pediatrics at the University of Iowa in Iowa City, in an interview with Medscape Diabetes & Endocrinology.
"These results are particularly nice to see in boys, since it seems they can become highly motivated to do exercise training. In particular, it looked like the boys were quite interested in weight training, which may be a nice modality to be able to treat them," Dr. Norris cochaired the session where the data were presented, but was not involved in the study.
The study was funded by the ADA. Dr. Lee and Dr. Norris have disclosed no relevant financial relationships.
American Diabetes Association (ADA) 70th Scientific Sessions: Abstract 22-OR. Presented June 25, 2010.
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Cite this: Exercise Alone Reduces Diabetes Risk in Obese Boys - Medscape - Jun 26, 2010.