Lipid Availability During Endurance Exercise In Visceral Fat Obese Men

Abstract

It is well known that plasma lipid availability and fat oxidation at rest are influenced by body fat distribution (visceral fat obesity [VF-Ob] vs. abdominal subcutaneous fat obesity [SF-Ob]). However, few studies have investigated lipid metabolism during endurance exercise in obese men. Moreover, the effects of body fat distribution on plasma lipid availability and fat oxidation during endurance exercise are not clear. PURPOSE The purpose of this study was to investigate whether body fat distribution influences fat metabolism during endurance exercise in obese men. METHODS Eleven sedentary men (body mass index [BMI] >25 kg/m2) were divided into the two groups: VF-Ob group (visceral fat area [VFA] >150 cm2, n = 6, 54.6 ± 8.9 yr) and SF-Ob group (VFA < 150 cm2, n = 5, 56.2 ±4.1 yr). All participants performed stationary cycle exercise for 60 minutes at 50% maximal oxygen uptake (VO2max). Respiratory gases and blood were sampled for substrate oxidation, hormone and metabolite analysis both at rest and during endurance exercise. RESULTS Plasma epinephrine, norepinephrine and insulin responses were not different between the two groups both at rest and during endurance exercise. Plasma free fatty acid (FFA) levels were greater in the VF-Ob group compared with the SF-Ob group for the last 40 min of exercise (P <0.05). Circulating plasma glycerol levels tended to be higher in the VF-Ob group than the SF-Ob group after the first 20 min of endurance exercise. A significant difference in plasma glycerol levels was observed only at 20 min of endurance exercise between the two groups (P <0.05). Total energy expenditure and fat oxidation were similar in both groups during endurance exercise. CONCLUSIONS During moderate endurance exercise, plasma lipid availability, but not energy expenditure or fat oxidation, differed by the type of body fat distribution with VF-Ob individuals demonstrating higher levels of plasma FFA. The differences may be caused by a characteristic of visceral fat that has a greater lipolytic response to catecholamines and a lower anti-lipolytic response to insulin compared with subcutaneous fat. Supported partly by the 21st century COE program, and the Tanaka Project of TARA.