Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise - a randomized controlled trial in overweight sedentary males

http://ajpregu.physiology.org/content/early/2012/07/30/ajpregu.00141.2012.abstract

 Abstract

The amount of weight loss induced by exercise is often disappointing. A diet-induced negative energy balance triggers compensatory mechanisms, e.g. lower metabolic rate and increased appetite. However, knowledge about potential compensatory mechanisms triggered by increased aerobic exercise is limited. A randomized controlled trial was performed in healthy sedentary moderately overweight young men to examine the effects of increasing doses of aerobic exercise on body composition, accumulated energy balance, and the degree of compensation. Eighteen participants were randomized to a continuous sedentary control group, 21 to a moderate (MOD; 300 kcal/day) and 22 to a high dose (HIGH; 600 kcal/day) exercise group for 13 weeks, corresponding to approximately 30 and 60 minutes of daily aerobic exercise, respectively. Body weight (MOD: -3.6kg, P<0.001; HIGH: -2.7kg, P=0.01) and fat mass (MOD: -4.0kg, P<0.001 and HIGH: -3.8kg, P<0.001) decreased similarly in both exercise groups. Although the exercise-induced energy expenditure in HIGH was twice that of MOD the resulting accumulated energy balance, calculated from changes in body composition, was not different (MOD: -39.6Mcal, HIGH: -34.3Mcal, NS). Energy balance was 83% more negative than expected in MOD, while it was 20% less negative than expected in HIGH. No statistically significant changes were found in energy intake or non-exercise physical activity that could explain the different compensatory responses associated with 30 vs. 60 min of daily aerobic exercise. In conclusion a similar body fat loss was obtained regardless of exercise dose. A moderate dose of exercise induced a markedly greater than expected negative energy balance, while a higher dose induced a small but quantifiable degree of compensation.

COMMENT:  Good news for busy people, thirty minutes of daily aerobic exercise is enough and increasing that to sixty minutes provides no additional benefit.