At 40 minutes of jogging fatty acids are burn. Fatty acids are produced in the process of lypolisis of the fat accumulated in the fat cells. If lipolysis is blocked as a result of e.g. acidification (too an intensive warm up), then despite of aerobic efforts mainly sugar supplies (glycogen) will be burnt and not fat. In case of sugar deficiency muscle proteins will be burnt for the energetic purposes that is for the so called catabolism. This is a case in a very dramatic diet.

Orma