Energy expenditure is high complex and regulated by the hypothalamus.
Daily energy expenditure is composed of three main components, the resting metabolic rate (RMR), the thermic effect of food (TEF) and the thermic effect of activity (TEA). The resting metabolic rate is the energy required by the body to maintain normal homeostatic functions and uses between 60 and 70% of total energy expended. This energy is required for body maintenance such as protein turnover and immune system functions. In an average man consuming 2500 calories a day, the resting metabolic rate might consume over 1750 of those calories, 25 % of which is utilised by the liver. The thermic effect of food is the increase in the energy expenditure for metabolising and storing the nutrients following food ingestion. This can make up around 10 % of the total energy expenditure. The thermic effect of activity makes up 15 to 30 % of energy expenditure and includes activity due to physical work and muscle activity, such as fidgeting and shivering. Purposeful exercise is only a small sub-component of the thermic effect of activity.
Despite the obvious complexities of energy regulation an oversimplified energy balance model has been adopted based on the ‘if you eat it, and don’t burn it, you’ll store it’ mantra. While on the surface this mantra appear logical, its simplification belies the truth. It is assumed people get fat because they are too lazy to exercise and too greedy to stop eating. Such oversimplifications of the energy balance of the body is common in medical textbooks. But missing out the complexities of resting metabolic rate, the thermic effect of food and the thermic effect of activity provides a thin veneer of validity to the oversimplified formula that is the current paradigm. Much of this has to do with the powerful food industry that spends millions lobbying the governments of the world to show that their foods are not unhealthy, but that people eat too much of it and do not exercise enough. Such companies also spend money associating with athletic events, to maintain the pretence that exercise causes weight loss in those who have in reality been poisoned by their foods.
In truth, energy balance is far more complicated than often presented. And understanding the regulation of the components that makes up the energy needs of the body is important if the causes of weight gain and weight loss are to be understood. For example, purposeful exercise is only a sub-component of thermic effect of activity, but its its contribution to the energy balance equation has been massively overstated. Most assume that weight loss will follow any programme of physical activity, but this is not true. Most people gain weight because they have a metabolic dysfunction. Exercising under such conditions will increase the thermic effect of activity. However, the resting metabolic rate or the thermic effect of food may fall to compensate for the energy outlay. Such compensatory regulation is often overlooked by proponents of the ‘eat-too-much, do-too-little’ hypothesis of weight gain either because they do not understand it, or because they have an agenda that requires an oversimplified model to hide their true intentions.
To fully understand the energy balance equation, the role played by the hypothalamus in regulating the energy needs of the body must be considered. The hypothalamus controls energy expenditure based on its perceived needs through its ability to change energy intake and energy expenditure. Evidence suggests that the abdominal obesity caused by metabolic syndrome is perceived by the hypothalamus as a state of starvation. This situation arises because leptin resistance develops in the hypothalamus when insulin resistance is present. Leptin is a signal molecule released from adipose tissue and its plasma levels therefore reflect the size of adipose tissue store. When the hypothalamus becomes resistant to this signal, the energy stores are perceived to be inadequate. As a result the hypothalamus regulates energy balance by increasing energy intake and decreasing energy expenditure. In this way the hypothalamus attempts to counter the perceived starvation state by accumulating adipose tissue to bolster stored energy reserves.
Under such circumstances forcibly increasing energy expenditure through physical activity is problematic. Because the exercise is not desirably to the energy requirements, the hypothalamus will compensate by causing reductions in resting metabolic rate or the reducing the thermic effect of food. This explains the total lack of long-term benefits to aerobic exercise in clinical trials and the anecdotal poor results of those who use exercise to lose weight. The art of weight loss is therefore not to force the hypothalamus to endure energy balance deficits it finds unappealing given the current metabolic milieu, because this strategy will surely result in countermeasures that cause no net gain. Instead, the hypothalamus must be persuaded to relinquish energy passively such that it is the desired option, and this can only be accomplished through reversing the metabolic dysfunction that causes leptin resistance. Ingestion of a high quality diet devoid of the metabolic poisons that the food industry has foisted upon us is the solution to this problem.
