ARS | Publication request: A 12-week aerobic exercise program reduces hepatic fat accumulation and insulin resistance in obese, Hispanic adolescents.

Submitted to: Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 9, 2009
Publication Date: February 12, 2010
Citation: Van Der Heijden, G., Wang, Z., Chu, Z., Sauer, P.J., Haymond, M.W., Rodriguez, L., Sunehag, A.L. 2010. A 12-week aerobic exercise program reduces hepatic fat accumulation and insulin resistance in obese, Hispanic adolescents. Obesity. 18(2):384-390.

Interpretive Summary: The rise in obesity-related morbidity in children and adolescents requires urgent prevention and treatment strategies. Currently, only limited data are available on the effects of exercise programs on insulin resistance, and total body fat, belly fat, and fat around the inner organs of the belly. We hypothesized that a 12-week controlled aerobic exercise program without the intent of weight loss, reduces subject's fat content and decreases insulin resistance in sedentary Hispanic adolescents. Fitness, lean body mass (muscle mass), total body fat, belly fat, and fat around the inner organs of the belly as well as, fat in the liver and a number of metabolic parameters were measured before and after the 12 week exercise program. The results demonstrate that this aerobic exercise program increased the fitness, reduced fat in the liver, and around the inner organs, and improved the sensitivity to insulin (the most important hormone controlling sugar metabolism). These effects are very important to prevent obesity related illnesses and show exercise without the intent of weight loss can be effective in reducing total body fat.

Technical Abstract: The rise in obesity-related morbidity in children and adolescents requires urgent prevention and treatment strategies. Currently, only limited data are available on the effects of exercise programs on insulin resistance, and visceral, hepatic, and intramyocellular fat accumulation. We hypothesized that a 12-week controlled aerobic exercise program without weight loss, reduces fat content and decreases insulin resistance in sedentary Hispanic adolescents. Twenty-nine postpubertal (Tanner stage IV and V), Hispanic adolescents, 15 obese (7 boys, 8 girls; 15.6 +/- 0.4 years; 33.7 +/- 1.1 kg/m(2); 38.3 +/- 1.5% body fat) and 14 lean (10 boys, 4 girls; 15.1 +/- 0.3 years; 20.6 +/- 0.8 kg/m(2); 18.9 +/- 1.5% body fat), completed a 12-week aerobic exercise program (4 x 30 min/week at > or =70% of peak oxygen consumption (VO(2)peak). Measurements of cardiovascular fitness, visceral, hepatic, and intramyocellular fat content (magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS)), and insulin resistance were obtained at baseline and postexercise. In both groups, fitness increased (obese: 13 +/- 2%, lean: 16 +/- 4%; both P < 0.01). In obese participants, intramyocellular fat remained unchanged, whereas, hepatic fat content decreased from 8.9 +/- 3.2 to 5.6 +/- 1.8%; P < 0.05 and visceral fat content from 54.7 +/- 6.0 to 49.6 +/- 5.5 cm (2); P < 0.05. Insulin resistance decreased indicated by decreased fasting insulin (21.8 +/- 2.7 to 18.2 +/- 2.4 microU/ml; P < 0.01), and homeostasis model assessment of insulin resistance (HOMA (IR)) (4.9 +/- 0.7 to 4.1 +/- 0.6; P < 0.01). The decrease in visceral fat correlated with the decrease in fasting insulin (R (2) = 0.40; P < 0.05). No significant changes were observed in any parameter in lean participants except a small increase in lean body mass (LBM). Thus, a controlled aerobic exercise program, without weight loss, reduced hepatic and visceral fat accumulation, and decreased insulin resistance in obese adolescents.