any people consume low fat foods under the erroneous belief that they will not accumulate body fat. This over simplistic and quite frankly absurd notion that dietary fat is the only cause of body fat accumulation is still widely held amongst the general population. In response to this ignorance, the ever opportunistic food industry has successfully marketed a wide range of low fat foods aimed at those wishing to lose weight. That these foods are more likely to cause weight gain than the higher fat alternatives is a valid viewpoint based on the scientific studies showing that sugar is the probable cause of obesity. Most who consume such products do not understand that overconsumption of sugar will result in the endogenous production of fatty acids and the accumulation of body fat. In fact sugar consumption is much more likely to result in weight gain because dietary fructose is the likely cause of mammalian insulin resistance.
Studies dating back decades have shown that carbohydrate consumption causes increased de novo lipogenesis once glycogen reserves in the liver and muscle have been filled. For example, one study published in the American Journal of Clinical Nutrition in 19881 investigated the fate of excess carbohydrate consumption in men. The researchers depleted the glycogen stores of the men using dietary restriction of carbohydrate (10 % of total calories) and calories (between 1994 and 1362 kcal/d) and increased physical activity. The subjects were then fed a higher carbohydrate diet (86 % of total calories) along with a higher calorie diet (3642 kcal/d). The researchers reported that the maximum storage capacity of glycogen in man is roughly 15 g per kg bodyweight, and accommodation of 500 grams of glycogen is possible before excess carbohydrate is converted to fatty acids and then triglycerides for storage.
Once the glycogen stores were saturated, the subjects synthesised around 150 g of lipids per day through hepatic de novo lipogenesis. In addition to the conversion of carbohydrate to fatty acids, massive increases in carbohydrate oxidation occurred in the subjects suggesting that the body tried to compensate for the influx of excess energy through use of carbohydrate as a source of energy and heat. Therefore carbohydrate overconsumption leads to the endogenous production of fatty acids, a causative agent in the development of insulin resistance. Exercise is probably beneficial at delaying the onset of insulin resistance and therefore offers some protection because it depletes glycogen stores. This decreases the problem of carbohydrate consumption because it increases the threshold at which carbohydrate intake spills over from glycogen replenishment to fatty acid synthesis.
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