ery-low calorie diets produce short-term weight loss but are often associated with a decrease in fat free mass that reduces resting metabolic rate and prevents further weight loss. Because weight training is anabolic and can increase fat free mass, it might be expected to minimise the loss of fat free mass when combined with a very low calorie diet. To test this hypothesis, researchers1 investigated the effects of a very low calorie diets alone, and in combination with endurance and resistance training, in order to determine the changes in fat free mass and resting metabolic rate. Sixty-nine obese females were administered a 90 day liquid diet providing 522 kcal and then assigned randomly to receive the diet, the diet plus chaperoned endurance exercise (60 min 4 days per week), diet plus resistance training (3 sets of 8-12 repetitions 4 days per week), or diet plus both weight training and endurance exercise.
The results showed that there were no significant differences between the groups in terms of changes in body weight, percentage fat, fat weight or fat free mass. The declines in resting metabolic rate seen in the subject of all groups were in the range on 7 to 12 % from their baseline values. Losses in strength were seen for the diet and diet plus endurance groups of around 6 % from baseline, whereas strength increased by around 3 % and 10 % in the endurance plus weight training and weight training groups, respectively. Overall work capacity only increased significantly (16 %) from baseline in the endurance plus strength training group. Therefore in this study, there was no benefit to the body composition of obese females when endurance training or resistance training was combined with energy restriction, which raises questions about recommendations to exercise in order to lose weight.
Weight loss over 90 days was 20.4, 21.4, 20.9 and 22.9 kg in the diet, diet plus endurance, diet plus resistance exercise, and diet plus endurance and resistance exercise, respectively. However, this included a mean loss of 4.6 kg in fat free mass, and resting metabolic rate declined by 10.4 % from baseline. The low protein levels within the diet (50 g) may have been a contributory factor in the poor results of the exercise regimens. In addition, this was a short-term study and it is unclear whether weight loss would be maintainable after cessation of the extreme calorie restriction, especially considering the reduction in resting metabolic rate. Exercise has consistently shown an inability to cause weight loss over and above that achievable by dietary improvements alone, in a number of well designed studies. Improving the quality of diet is able to cause body composition improvements equal to those of exercise (here).
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