Strength exercise improves muscle mass and hepatic insulin sensitivity in obese youth.
BACKGROUND
Data on the metabolic effects of resistance exercise (strength training) in adolescents are limited.


OBJECTIVE
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.


METHODS
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 × fasting insulin). Glucose production rate (GPR), gluconeogenesis, and glycogenolysis were quantified using stable isotope gas chromatography/mass spectrometry techniques.


RESULTS
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).


CONCLUSIONS
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.
Van Der Heijden
Gert-Jan
GJ
Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
Wang
Zhiyue J
ZJ
Chu
Zili
Z
Toffolo
Gianna
G
Manesso
Erica
E
Sauer
Pieter J J
PJ
Sunehag
Agneta L
AL
D000273:Adipose Tissue / Q000378:metabolism; D000293:Adolescent; D005260:Female; D006801:Humans; D007328:Insulin / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000502:physiology*; D009765:Obesity; D055070:Resistance Training
D007328:Insulin