Abstract (Numao S in NAASO 2005)

FAT AVAILABILITY AND OXIDATION DURING HIGH-INTENSITY ENDURANCE EXERCISE IN VISCERAL AND SUBCUTANEOUS FAT OBESITY

Shigeharu Numao, Yoichi Hayashi, Yasutomi Katayama, Tomoaki Matsuo, Tsugio Tomita, Kiyoji Tanaka

Background: Few studies have investigated the effects of obesity phenotype on fat metabolism during endurance exercise. Also, it has not been determined whether obesity phenotype influences fat metabolism during “high-intensity” endurance exercise.
Purpose: The purpose of this study was to compare the plasma fat availability and oxidation between obesity phenotype during “high-intensity” endurance exercise.
Methods: Twelve sedentary obese men (BMI > 25 kg/m2) were divided into two groups using visceral fat area (VFA) of 150 cm2: VF obesity (VF-Ob) (n = 7, 52.9 ± 2.3 yr) and subcutaneous fat obesity (SF-Ob) (n = 5, 56.2 ± 4.0 yr). All participants performed stationary cycle ergometer exercise for 60 min at 70% maximal oxygen uptake. Both at rest and during endurance exercise, respiratory gases (per 5 min) and blood (per 30 min) were sampled for substrate oxidation, hormone and metabolite analysis.
Results: Plasma epinephrine, norepinephrine and insulin responses were not different between the two groups during endurance exercise. There was a significant effect of group by time interaction (P < 0.05) in the concentration of plasma free fatty acid (FFA) and glycerol. The concentrations of FFA (P < 0.05) and glycerol (P = 0.07) in VF-Ob were higher than those in SF-Ob after 60 min of exercise. The change of FFA concentration (P < 0.05) and glycerol (P = 0.08) were also greater in the VF-Ob compared with the SF-Ob at the middle of the exercise time. However, fat oxidation was similar in both groups throughout the exercise.
Conclusion: During high-intensity endurance exercise, fat availability, but not fat oxidation, was higher in the obesity phenotype with VF-Ob individuals demonstrating higher levels of plasma fat.

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