Title: Strength exercise improves muscle mass and hepatic insulin sensitivity in obese youth Authors
|Van Der Heijden, Gert -|
|Wang, Zhiyue -|
|Chu, Zili -|
|Toffolo, Gianna -|
|Manesso, Erica -|
|Sauer, Pieter -|
|Sunehag, Agneta -|
Submitted to: Medicine and Science in Sports and Exercise
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2010
Publication Date: March 25, 2010
Citation: Van Der Heijden, G.J., Wang, Z.J., Chu, Z., Toffolo, G., Manesso, E., Sauer, P.J., Sunehag, A.L. 2010. Strength exercise improves muscle mass and hepatic insulin sensitivity in obese youth. Medicine and Science in Sports and Exercise. 42(11):1973-1980. Interpretive Summary: Physical activity is a primary intervention in the combat against obesity and related disorders. However, data on the metabolic effects of strength training in adolescents are limited. Twelve Hispanic obese teenagers, 6 girls and 6 boys, completed a 12 week strength exercise program. The attendance was very good with about 96% completed sessions. 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 demonstrated that this strength exercise program that was well accepted by the participants, increased strength and muscle mass, which is very important at least for the self esteem of obese adolescents. Further, the sensitivity to insulin (the most important hormone controlling sugar metabolism) in the liver increased. However, the program did not affect any of the fat deposits or the sensitivity to insulin in the muscles. A program combining strength training and aerobic exercises may be a viable strategy to achieve the positive effects of both exercises.
Technical Abstract: Data on the metabolic effects of resistance exercise (strength training) in adolescents are limited. The objective of this study was to determine whether a controlled resistance exercise program without dietary intervention or weight loss reduces body fat accumulation, increases lean body mass, and improves insulin sensitivity and glucose metabolism in sedentary obese Hispanic adolescents. Twelve obese adolescents (age = 15.5 +/- 0.5 yr, body mass index = 35.3 +/- 0.8 kg/m; 40.8% +/- 1.5% body fat), completed a 12-wk resistance exercise program (two times 1 h/wk, exercising all major muscle groups). At baseline and on completion of the program, body composition was measured by dual-energy x-ray absorptiometry, abdominal fat distribution was measured by magnetic resonance imaging, hepatic and intramyocellular fat was measured by magnetic resonance spectroscopy, peripheral insulin sensitivity was measured by the stable-label intravenous glucose tolerance test, and hepatic insulin sensitivity was measured by the hepatic insulin sensitivity index = 1000/ (GPR x fasting insulin). Glucose production rate (GPR), gluconeogenesis, and glycogenolysis were quantified using stable isotope gas chromatography/mass spectrometry techniques. All participants were normoglycemic. The exercise program resulted in significant strength gain in both upper and lower body muscle groups. Body weight increased from 97.0 +/- 3.8 to 99.6 +/- 4.2 kg (P < 0.01). The major part (~80%) was accounted for by increased lean body mass (55.7 +/- 2.8 to 57.9 +/- 3.0 kg, P </= 0.01). Total, visceral, hepatic, and intramyocellular fat contents remained unchanged. Hepatic insulin sensitivity increased by 24% +/- 9% (P < 0.05), whereas peripheral insulin sensitivity did not change significantly. GPR decreased by 8% +/- 1% (P < 0.01) because of a 12% +/- 5% decrease in glycogenolysis (P < 0.05). We conclude that a controlled resistance exercise program without weight loss increases strength and lean body mass, improves hepatic insulin sensitivity, and decreases GPR without affecting total fat mass or visceral, hepatic, and intramyocellular fat contents.