Strength Exercise Improves Muscle Mass and Hepatic Insulin Sensitivity in Obese Youth

Abstract

Introduction Data are limited on the metabolic effects of resistance exercise (strength training) in adolescents. Purpose 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 (15.5±0.5y; 35.3 ±0.8kg/m2;40.8±1.5% body fat), completed a 12 wk resistance exercise program (2×1h/wk, exercising all major muscle groups). At baseline and completion of the program, body composition was measured by DXA, abdominal fat distribution by Magnetic Resonance Imaging, hepatic and intramyocellular fat by Magnetic Resonance Spectroscopy, peripheral insulin sensitivity by the Stable Labeled IV Glucose Tolerance Test and hepatic insulin sensitivity 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 content remained unchanged. Hepatic insulin sensitivity increased by 24±9% (p<0.05), while peripheral insulin sensitivity did not change significantly. GPR decreased by 8±1% (p<0.01) due to a 12±5% decrease in glycogenolysis (p<0.05). Conclusion 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 content.

Treatment of Non-Alcoholic Fatty Liver Disease

“…Aerobic exercise increases skeletal muscle insulin sensitivity, thereby reversing insulin resistance, which is one of the key pathophysiological mechanisms causing NAFLD [24,25]. Studies examining moderate intensity training, high-intensity training and resistance exercise have shown improved liver enzymes and reduced steatosis, independent of weight loss [26,27,28].…”

Strength Capacity and Cardiometabolic Risk Clustering in Adolescents

“…6,7 There is also compelling evidence to support the efficacy of progressive RE for glycemic control among children and adolescents, 8 even in the absence of weight loss. 9,10 However, because RE is known to elicit a potent insulin-sensitizing affect for hours after a single bout of training, [11][12][13] there is some speculation about whether it is merely the repeated acute responses to habitual RE that drive benefits for metabolic health, rather than any adaptive-response per se. Regardless, because childhood activity level appears to track into adulthood, 14 RE may be a vital component of healthrelated physical activity for metabolic fitness in children and adolescents.…”

Fructose Consumption in the Development of Obesity and the Effects of Different Protocols of Physical Exercise on the Hepatic Metabolism

“…After 72 hours of the end of the session, the plasma TG levels were reduced only in subjects who trained in the intensities of 50% and 75% of 1RM, while those trained at 90% and 100% showed no differences. Also, after an exercise session, the sensitivity to insulin in the hepatic tissue was improved at 8% ± 1% reductions in glucose production rate and 12% ± 5% glycogenolysis [97]. In summary, the strength exercise promoted consistent improvements in the metabolism of rodents fed a high fructose diet [49].…”