![]() ![]() Similarly, no fat loss effect was observed following 12-weeks of aerobic training at both low-intensity (40% VO 2max) and moderate-intensity (70% VO 2max) among obese men (∼350 kcal, three times per week) ( Aggel-Leijssen et al., 2002). A 15-weeks sprint training depending primarily on anaerobic metabolism effectively decreases abdominal fat, whereas moderate-intensity exercise training depending on aerobic metabolism with similar energy expenditure (60% VO 2max consuming ∼200 kcal, three times per week) failed to decrease body fat in young women ( Trapp et al., 2008). Neither aerobic exercise nor resistance exercise increases 24-h fatty acid oxidation ( Melanson et al., 2002).Ī number of clinical studies divulges paradox between fat burning and fat loss outcome. Furthermore, increased energy expenditure, especially during high intensity exercise, comes from fuel stored in skeletal muscle (mostly glycogen), not adipose tissue (fatty acids) ( Romijn et al., 1993). However, the absolute energy contribution from plasma fatty acids (assuming all from adipose tissue) decreases as exercise intensity increases (from 25 to 85% VO 2max) and is consistent with decreased tissue fatty acid uptake during exercise ( Romijn et al., 1993). Increased lipolysis with elevated circulating fatty acids together with increased oxygen consumption during exercise seems to favor this explanation ( Romijn et al., 1993 Mora-Rodriguez and Coyle, 2000). This theory is built on the intuition that exercise as an energy consuming behavior will increase fatty acid oxidation from abdominal fat stores compared with sedentary condition, and thus accounts for the fat loss outcomes of exercise training ( Abbasi, 2019). Fat burning is a classic theory to describe the abdominal fat-reducing outcome of exercise training. Therefore, meal arrangement at the time when muscle has the greatest reconstruction demand for carbon and nitrogen could decrease abdominal fat accumulation while increasing muscle mass and tissue repair.Įxercise training decreases abdominal fat, in which high-intensity exercise produces more prominent fat loss than low and moderate intensity exercise ( Vissers et al., 2013 Viana et al., 2019). The magnitude of lipolysis (fatty acid release from adipocytes) and the amount of post-meal carbon and nitrogen returning to abdominal adipose tissue determines the final fat tissue mass. In brief, carbon and nitrogen redistribution to challenged tissues (muscle and lungs) for fuel replenishment and cell regeneration against abdominal adipose tissue seems to be the fundamental mechanism underlying the intensity-dependent fat loss effect of exercise. In this review, alternative perspectives to explain the fat loss outcome are discussed. ![]() The unchanged 24-h fatty acid oxidation during and after exercise does not provide support to the causality between fat burning and fat loss. Nevertheless, increasing exercise intensity decreases oxidation of fatty acids derived from adipose tissue despite elevated lipolysis. The fat loss effect of exercise has been intuitively thought to result from increased fat burning during and after exercise, defined by conversion of fatty acid into carbon dioxide in consumption of oxygen. 2Laboratory of Exercise Biochemistry, College of Kinesiology, University of Taipei, Taipei, TaiwanĮxercise training decreases abdominal fat in an intensity-dependent manner.1Department of Health Sciences, College of William and Mary, Williamsburg, VA, United States. ![]()
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