The energy balance theory of weight gain claims that excess body fat is a result of a positive energy balance that causes a gradual accumulation of fat. This overly simple explanation suggest that greed and laziness on the part of the individual is the main driver of obesity. Proponents of such a theory claim that such weight gain can be reversed by simply increasing the physical activity levels and reducing the energy intake, in order to create a negative energy balance. This is suggested to force the body to use the accumulated fat as a source of energy, producing a gradual reduction in adipose tissue. However this theory is seriously flawed because it does not take into account the quality of the food or the counter regulatory mechanisms that can be put in place by the hypothalamus to prevent fat loss. Weight gain is actually a condition of perceived starvation, and just as giving a starving man a low calorie diet and hard physical labour causes a deterioration in health, so too does applying the same to an obese individual.
One of the main problems with low calorie diets is that they cause a negative energy and nitrogen balance, and this causes a loss of skeletal muscle. This loss of skeletal muscle causes a reduction in the resting metabolic rate (RMR) which is detrimental to long term body composition improvements. Many studies have measured the weight loss following administration of a low or very low calorie diet and there is strong evidence from these studies that nearly half of all weight lost is in the form of skeletal muscle. For example, in one study1, researchers fed obese subjects a low calorie diet of between 500 and 700 kcals for 5 months as a high protein liquid formula. The liquid formula provided 1.5 grams of protein per kilogram of lean body mass and was designed to provide 9 kcal of energy per kilogram of body weight per day. Total weight loss on the diet was between 20 and 25 % of the body weight of the subjects, but of this lean mass accounted for 36 % of the total weight lost in the first 5 weeks.
The fact that two of the subjects were in negative nitrogen balance for the first 4 weeks in not surprising. As the diet progressed the protein loss decreased to 10 % of the total weight lost, however, the damage had already been done. This loss of skeletal mass is very important, because many studies are now showing that the resultant reduction in resting metabolic rate is semi permanent and can last for years or even decades. The lowered resting metabolic rate is the main reason that weight regain in the form of fat is almost inevitable on these types of diet. As the resting metabolic rate falls, the energy requirement of the body falls concomitantly. This means that when the diet ends and normal eating is resumed, fat accumulation accelerates and a cycle of yo yo dieting, that is common is serial dieters, commences. Energy is restricted again, more skeletal muscle mass is lost and more damage is done to the metabolism of the individual. Restoration of the resting metabolic rate through muscle growth is the solution to this problem.
Dr Robert Barrington’s Nutritional Comments: The key to effective long term weight loss is the maintenance of the resting metabolic rate. This means that muscle mass must be maintained or even increased if improvements in body composition are to become evident. For this to happen a high quality high protein diet must be consumed. In addition, some form of resistance training that causes hypertrophy of skeletal muscle must be undertaken. Building muscle causes fat loss. If you are scared of building muscle then you will never improve your body composition. Seeing exercise as a way to build muscle rather than a way to ‘burn fat’ is the first step in the long journey of successful weight loss.
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