The energy balance theory of weight gain states that the body weight of an individual is a sum of the food intake (energy in), the resting metabolic rate (the energy utilised for basal metabolic needs) and exercise (energy utilised in physical activity). As the saying goes, ‘if you eat it and don’t burn it, you’ll store it’. This is the mantra of the proponents of the energy balance equation theory of weight gain, who claim that weight gain is simply a case of eating too much food and doing too little exercise. This situation creates a positive energy balance that leads to the accumulation of body fat. In contrast, proponents of the energy balance theory of weight gain claim that weight loss is achievable by creating a negative energy balance through increased physical activity and decreased energy intake. By tipping the energy balance to negative, through exercise and low calorie diets, many people believe their body’s will use fat as a source of energy and that as a result their body composition will improve.
However. the nutritional literature does not support such a simplistic viewpoint and this explains the failure of low energy diets and exercise regimens to cause long term weight loss. The problem with the energy balance equation used in medical textbooks is that since it was formulated, our understanding of factors such as skeletal muscle loss, insulin resistance, nitrogen balance, leptin resistance and the different types of body fat have increased. These other factors can modulate energy expenditure and energy intake and thus the equation becomes a useless tool without deeper consideration. One of the problems with low calorie diets for example, is that they cause muscle loss and fat loss, and this affects the metabolic rate and thus energy metabolism is a semi-permanent way. In fact the role of muscle as a store of energy is often overlooked by those who seek as simplistic explanation to support their view that weight gain is a result of laziness and greed, because muscle is affected by both energy and nitrogen intake.
Based on the energy balance equation, one would expect it to be impossible to build skeletal muscle while in a negative or near zero energy balance. One cannot after all build something from nothing, right? However, anecdotal evidence and scientific observations in peer review papers do not support this contention. In fact, muscle is able to be built with a positive nitrogen balance, but a negative energy balance. In one study1, the effects of an increasing nitrogen intake were studied in patients who were nutritionally deficient and being fed through total parenteral nutrition. The patients received either a high or low nitrogen content to their diet (either 180 or 360 mg per kg per day) while energy was close to zero balance. With the high nitrogen diet, energy expenditure increased by around 10 %, and this was likely a reflection of the improvements in nitrogen retention that caused a net gain in skeletal muscle. How this is possible is not explainable by the energy balance theory of weight gain.
Dr Robert Barrington’s Comments: It is true that the above study was performed on nutritionally depleted subjects and the nitrogen retention rates are greater for such individuals compared to healthy controls. However, it does not explain how positive nitrogen balance can be maintained long term on energy balances close to or at zero. To create new muscle tissue energy must be provided, yet at no net increase in energy intakes, skeletal muscle accumulation is possible. If calorie intake was negative, why did the subjects not use the dietary nitrogen (protein) as a source of energy? Why was it used to build muscle despite the energy requirements of the body not being met? Such a situation can also be seen in growing organisms, where it has been shown that zero energy balance creates rapid growth if enough nitrogen is supplied in the diet in the form of protein. Because growth of skeletal muscle is clearly possible at zero or negative energy balances, it is not possible to conclude that a negative energy balance will cause weight loss, or that weight gain is caused by too much food or too little exercise. This throws further spanners in the works when considering the mainstream theory of weight loss through ‘dieting’ and exercise.
RdB
