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Abstract (Numao S in ACSM 2005)
Background: 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 two groups: VF-Ob (visceral fat area
(VFA) > 150 cm2, n = 6, 54.6 ± 8.9 yr) and SF-Ob (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). Both at rest and
during endurance exercise, respiratory gases and blood were sampled
for substrate oxidation, hormone and metabolite analysis in each participant.
Results: Plasma epinephrine, norepinephrine and insulin
responses were not different between the two obese 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 endurance 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 obese groups (P < 0.05). Total energy expenditure
and fat oxidation were similar during exercise in both groups.
Conclusion: 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 free fatty acids. The differences may be caused
by a characteristic of visceral fat that, compared with subcutaneous
fat, has a greater lipolytic response to catecholamines and an attenuated
anti-lipolytic response to insulin.
Supported partly by the 21st century COE program, and the Tanaka Project
of TARA.