Originally Posted by mrm14
Aus, I always thought that the first thing one would metabolize off was the body fat then the muscle mass after the body fat was diminished. Then after awhile the body goes into the starvation mode where the body, for lack of better words, trains itself to keep and store fat more than it usually would otherwise. Thats why alot of folks that go on starvation diets usually gain more weight after they go off those diets. Am I close on this theory?
The first source that the body converts into energy when it is using the aerobic energy system is glucose in the blood and after that, glucogen stored in the muscles. Glucogen is the body's way of storing carbohydrates that are ingested from your diet. The glucogen stores in the muscle last for approximately 40 mins when participating in moderate-intensity aerobic workout. As a point of reference, if you can carry out a normal conversation, you're not working in this zone.
After this point, yes the body starts to metabolise fats, and a long time after, protein in the muscles. You are partially right about the starvation diet; if the body does not receive adequate calories to perform it's basic functions such as breathing, thinking, digestion, etc (between 1200-1500cal for gals, 1500-2000cal for guys), the next time it does receive above that number, it stores all of the excess energy as fat, not as carbohydrate. This is due to the fact that fats are much more energy-rich than carbohydrates when metabolised. Starvation diets are extremely unhealthy, and frequently lead to more weight being put back on that what was originally lost.