Tuesday, May 5, 2009

The Drawbacks of Dieting – Muscle Loss

Along with the good effects of dieting, a lot of bad things start to happen. Basically, when you diet, the chemicals in your body send a message to your brain saying that your body is not getting enough food. This causes changes in the various neuro-chemicals stimulating a number of negative adaptations. I want you to note that the response is not immediate; there is a lag time between the changes in all of these hormones and the body's response. But that's not all.
There are also many other adaptations which occur when you diet, so let's look at some of those. First and foremost, the drop in leptin directly affects liver, skeletal muscle and fat cell metabolism, mostly for the worse. While the drop in Insulin mentioned above causes better fat mobilization, it causes other problems. Insulin is anti-catabolic to muscle, inhibiting muscle breakdown. The increase in cortisol that occurs with dieting enhances protein breakdown as well as stimulating the conversion of protein to glucose in the liver. Additionally, a fall in energy state of the muscle impairs protein synthesis (although it increases fatty acid oxidation). The mechanism behind this is more detail than I want to get into here. But the combined effect of these processes is that protein synthesis is decreased and breakdown is accelerated, eventually resulting in muscle loss.

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