Calorie Partitioning: Part 2
So you start your diet, reducing carbs, calories or both. Blood glucose and insulin levels are going to be reduced. This is good, it releases the ‘block’ on fat mobilization. Additionally, catecholamine release typically goes up, further increasing fat utilization. Blood levels of fatty acids will start to increase. This is good, as it tends to promote fat burning in tissues such as liver and muscle. This effect is facilitated if you deplete liver and muscle glycogen as glycogen depletion tends to increase the use of fatty acids for fuel. The increas in blood fatty acid levels also has the short-term effect of causing insulin resistance which, as I mentioned, is a good thing on a diet since it spares glucose and helps promote fat oxidation. So far, so good, right?
Calorie Partitioning: Part 1
At a very fundamental level, the problem that natural bodybuilders and athletes have is one of partitioning; that is, where the calories go when you eat more of them or come from when you eat less of them. In an ideal universe, every calorie you ate would go to muscle tissue, with none going into fat cells; you’d gain 100% muscle and no fat. In that same ideal universe, every calorie used during dieting would come from fat stores; you’d lose 100% fat and no muscle. Unfortunately, we don’t live in an ideal universe.
Initial Body Fat and Body Composition Changes
In that current data indicates that each pound of muscle might burn an additional 6 calories (as opposed to older values of 25-40 cal/lb or even higher) (1), this argument is no longer tenable; to significantly affect metabolic rate would require a monstrous gain of muscle mass, far more than you could gain in 3-4 weeks.
