AEROBIC-OXIDATIVE PROFILE OF SKELETAL MUSCLE CONTRIBUTES TO DIFFERENCES IN BODY FAT GAIN OVER 13 YEARS IN HUMAN 374

The purpose of this study was to determine the role of the metabolic profile of skeletal muscle in the variation in body weight and fat gain over time. Body weight (BW; N=108) and the sum of 6 different skinfold thicknesses(S6S; N=29) were obtained in 1982 and again in 1995 in adult (from 20 to 31 years of age) men and women. The proportion of type 1 fibers (% type I) and activity of oxoglutarate dehydrogenase (OGDH), a marker enzyme for the Krebs cycle, were determined in 1982 from biopsy samples of the vastus lateralis muscle. Significant and variable gains in BW (from 65±12 to 72±13 kg; p≤0.001) and S6S (from 63±27 to 79±32 mm; p≤0.001) were observed over the 13-yr period. The% type I fiber and OGDH activity in 1982 ranged from 20 to 86% and 0.30 to 1.92 U/g ww, respectively. No significant relationship was observed between changes in BW (r=0.07) or S6S(r=-0.06) and% type I fiber. A modest and negative correlation (r=-0.18; p=0.06) was found between BW gain and OGDH activity. The correlation reached-0.40 (p<0.05) between S6S gain and OGDH activity. The results reveal that 20% of the variance in body fat gain can be explained by specific characteristics of skeletal muscle. A low skeletal muscle aerobic-oxidative profile, but not the% of type I muscle fibers, contributes to the proneness to gain body fat over time and may be involved in the aetiology of obesity.