Fatty acid kinetic responses to exercise. Effects of obesity, body fat distribution, and energy-restricted diet.

Abstract

Upper body obesity (UB Ob) is associated with a reduced net free fatty acid (FFA) response to epinephrine compared with nonobese (Non Ob) and lower-body obese (LB Ob) women. Because catecholamines regulate some of the metabolic responses to exercise, we hypothesized that UB Ob would have a reduced net FFA response to exercise. Plasma FFA rate of appearance (Ra) (11-"4Clpalmitate) and fatty acid oxidation (indirect calorimetry) were therefore measured during 2.5 h of stationary bicycle exercise (45% VO2 peak) in 13 UB Ob, 11 LB Ob, and 8 Non Ob premenopausal women. 10 UB Ob and 8 LB Ob women were retested after an -8-kg weight loss. Results: During exercise Non Ob and LB Ob women had greater increments in FFA availability (51±7 and 53±8 mmol, respectively) than UB Ob women (27±4 mmol, P < 0.05). Total exercise FFA availability and fatty acid oxidation were not different between Non Ob, LB Ob, and UB Ob women, however. Following weight loss (-8 kg), the FFA response to exercise increased (P < 0.01) and remained greater (P < 0.05) in LB Ob than in UB Ob women. In conclusion, the FFA response to exercise was reduced in UB Ob women before-and after weight loss, but no effects on fatty acid oxidation were apparent. (J. Clin. Invest. 1993. 92:255-261.)

Effects of obesity phenotype on fat metabolism in obese men during endurance exercise

“…The fat availability in VF-Ob and SF-Ob men during endurance exercise observed in our study was inconsistent with data from previous studies that have investigated fat metabolism between two obesity phenotypes in obese women during endurance exercise. 18,19 The reasons for the discrepancy between the present study and previous studies 18,19 can be accounted for by several other factors. The first factor is the baseline of the plasma insulin concentration.…”

“…35,36 In addition, the strongest factor on our results is the difference in the subject's gender between the present study and earlier ones. 18,19 Lipolysis of visceral and subcutaneous adipocytes has been reported to differ between obese men and women. Lonnqvist et al 37 observed obese men were 12 times higher in the lipolytic b 3 -adrenoreceptor sensitivity of visceral adipocytes and 17 times lower in the antilipolytic a 2 -adrenoreceptor sensitivity of visceral adipocytes compared with obese women.…”

“…Kanaley et al 18 reported that the increments in free fatty acid (FFA) availability during endurance exercise were greater in lower body (LB) obese women than upper body (UB) obesity women. However, no differences were observed in total FFA availability and fat oxidation between LB and UB women.…”

Normal mitochondrial function and increased fat oxidation capacity in leg and arm muscles in obese humans

“…In contrast to our results, it has been reported that fat oxidation capacity is reduced in extremely O individuals, even after weight loss. 8,11,42 However, in these studies, subjects were not matched for physical fitness and physical activity. Another important finding from this study is that PO subjects with a steady body composition retain an increased capacity to oxidize fat during leg exercise but not during arm exercise when compared with Cs of similar body composition.…”

“…1 In fact, there seems to be a consensus or almost a paradigm that obesity is accompanied by an impaired ability to oxidize fat during exercise, [2][3][4][5][6] although not all studies demonstrate this. 7,8 In line with this notion, there is evidence that mitochondrial oxidative capacity is decreased in skeletal muscle of O 9 and type 2 diabetic individuals, [10][11][12] although not all agree. 13 In sedentary O subjects, a moderate weight loss accompanied by an improved aerobic capacity leads to a normalization of mitochondrial oxidative capacity and insulin resistance.…”