A Short Primer on the “Fat-Loss Decision Maker” Leptin

December 13th, 2009 by

While not everything is known about leptin, what is known is that leptin levels are related to things like insulin, your caloric intake and your current level of body fat. Think of it as one of the big “fat-loss decision makers”. The leaner you are relative to your normal bodyfat level, the lower your circulating levels of leptin are generally going to be. Under more normal circumstances, higher body fat, maintenance caloric intake, etc., leptin levels are higher. However, while on sub-maintenance calories, and particularly on low-carb diets where circulating insulin levels are low, leptin levels drop and they can drop quickly. Decreased leptin levels cause a cascade of other regulatory changes, namely a decrease in thyroid output and metabolic rate, as well as an increase in catabolic hormone activity and appetite. In an attempt to become more efficient, your body will try to adapt to make your newly lowered caloric intake its new maintenance intake; that is, it will make the necessary changes needed to do the same amount of work on less energy. Unfortunately, this usually means having to continuously lower calories or increase expenditure to maintain fat-loss progress, which inevitably makes it very hard to hold onto all your hard-earned muscle. There is only so far you can cut your calories and only so much cardio and training you can do. Remember – the diet has to be both functional and maintainable. Not to mention, this type of (all too common among competitors) dieting strategy really sets you up for a nasty rebound when you return to more ‘sane’ methods. None of this sounds too good does it? There has to be a better way, and there is. Planned and structured days of high calories and high carbohydrates may help with this.

As previously mentioned, there are benefits to both low-carb intakes and to high-carb intakes. When carb intake is drastically reduced you create a temporarily greater caloric deficit. In addition, low-carb intakes result in decreased levels of circulating insulin, increased levels of the fat-burning catecholamines and therefore a much heightened rate of fat oxidation. Quite simply, when insulin levels are low, you create an environment in which fat is more likely to be used for energy. Low muscle glycogen, as a result of decreased carbohydrate intake, obviously results in depleted muscles, but there are benefits to this as well. Low muscle glycogen tends to promote a higher rate of free fatty acid burning. Result? More fat loss.

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