here is a common misconception that weight gain and obesity are caused by a positive energy balance. This ‘eat-too-much, do-too-little’ theory of weight gain states that overconsumption of food or underperformance of physical activity causes a positive energy balance that results in incremental accumulation of body fat. This erroneous belief is provably false from the nutritional literature, but is still widely held as true by many individuals. Based on this theory, many claim that weight loss for obese individuals is simply a case of causing a negative energy balance through increased physical activity in combination with decrease energy intake. Fasting is able to cause weight loss and many claim the reason for this is the reduction in the number of calories consumed. However, forced calorie restriction is not the reason that fasting is an effective solution for weight loss.
Obesity is caused by insensitivity in the insulin receptor. This is thought to be caused by overconsumption of fructose. Fructose has been shown to cause insulin resistance in as little as two weeks in animal models and these results have been confirmed by human studies. Fructose is problematic because it overloads the liver with energy and causes increase flux through the de novo lipogenesis pathway. This results in the overproduction of fatty acids, that are subsequently stored in the liver and skeletal muscle. These fatty acids may then interfere with the insulin signal cascade causing insulin resistance. The insulin resistance causes leptin resistance in the hypothalamus, and as a result the brain considers the adipose tissue in the body to be depleted relative to its actual content. This creates a physiological environment whereby the body is unable or unwilling to expend energy.
The treatment for obesity is to raise the quality of the diet. This means removing sources of fructose, such as sucrose containing foods, and simultaneously decreasing foods that exacerbate the release of insulin. Increasing whole grain foods and decreasing refined carbohydrates foods devoid of fibre has this effect. Any strategy that employs similar mechanisms will be effective at treating obesity. For this reason, low carbohydrate diets cause weight loss, even without calorie restriction because they remove refined carbohydrates and fructose from the diet, the two main causes of insulin resistance. Likewise, fasting removes these problematic compounds from the diet and this increases insulin sensitivity. Forced calorie restriction is usually not effective at causing weight loss because rather than improving the diet, the subjects simply eats less of the same poor quality foods.
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