The traditional model of body weight loss considers the only two factors relevant to weight loss to be energy consumed and exercise performed. In this model, energy balance is an equilibrium between these factors. Part of this assumption considers energy balance to therefore be under conscious control. In other words, weight loss is achieved by consciously providing the body with an energy deficit due and this in turn causes weight loss because the energy reserves of the body, or more specifically the stored fat, is used as a source of energy, and depleted. However, the scientific literature does not support this contention. Many studies have shown that forced energy depletion results not only body fat loss, but also serious health effects caused by loss of lean tissue and damage to normal metabolic and immune regulation. Further, when the period of energy restriction ceases, there is considerable and rapid weight gain that results in a deterioration of the body composition such that the dieter actually gains weight.
That the body has well designed unconscious homeostatic measures to maintain normal body weight, despite fluctuations in energy expenditure and energy intake, is often completely ignored or overlooked by proponents of the energy balance theory of weight change. Under normal conditions, signal molecules from the energy stores and gut relay information back to the central nervous system, and here the information is collated to alter behaviour to prevent large scale future changes in energy stores. If food intake decreases, ghrelin is released from the gut and this activates receptors in the brain to stimulate a number of orectic peptides that stimulate hunger and decrease the desire to perform physical activity. If food intake increases, hormones such as insulin, peptide YY and leptin activate receptors in the brain to stimulate a number of anorectic peptides, and these in turn increase metabolic rate, increase physical activity and reduce appetite. These systems thus allow maintenance of normal body weight.
Body weight gain is caused when the homeostatic systems fail to function correctly. It is known what causes this failure and many studies have shown that the main culprit is low quality food eaten regularly as part of a low quality diet. Such diets are usually devoid of meaningful levels of essential nutrients including vitamins, minerals and essential fatty acids, high in refined carbohydrates including refined crystalline sugars, high in trans fatty acids, and low in fibre. Such a diet is often called the typical Western diet, and is the main diet of most of Western Europe, North America and Australasia. It is no coincidence that these countries have a high prevalence of obesity and obesity related conditions such as diabetes and cardiovascular disease. In particular, consumption of sugars has increased considerably in these areas in the last 50 years or so, and this has been accompanied by increased consumption of nutrient poor foods, and an accompanying increase in the rates of overweight and obesity.
Consuming low quality foods leads to disruption of the homeostatic mechanisms that control energy balance because they cause insulin resistance, and this in turn disrupts the insulin signal which decreases appetite. Highly refined carbohydrates lead to the development of insulin resistance because the starch is quickly digested and this creates a condition of nutrient overload in the circulation. The rapid rise in blood sugar floods cells with energy and as a protective measure against the generation of free radicals, these cells reduce further glucose uptake by decreasing the sensitivity of the insulin receptor. Fructose may also induce insulin resistance because it stimulates flux through the de novo lipogenesis pathway, and this then increases the circulation of fatty acids, that may accumulate in tissues and desensitise the insulin receptor. Trans fats may decrease insulin sensitivity through interference with the essential fatty acid pathway. Avoiding low quality foods may improve insulin sensitivity and reverse weight gain.
RdB
