As fat molecules are broken down, the mass of the adipose tissue decreases. This decrease in size causes a decrease in body weight and size. Remember that it takes an enormous amount of energy to break down fat molecules to smaller molecules. Even though fat molecules are easily stored in tissues, they are not as easy to retrieve for utilization. Exercise Aerobic exercise is that which will allow food substances to metabolize properly with the addition of oxygen.
Anaerobic exercise requires no oxygen for metabolism.
In the first step of cellular respiration, oxygen is needed to break down glucose molecules into pyruvic acid. Pyruvic acid is then needed for the other steps of cellular respiration to proceed. Cellular respiration in cells is necessary for other activities of the body to function properly. If oxygen is not available, then glucose molecules will break down into lactic acid. Muscle contraction, neuronal synapsing, digestion, and other processes of the body all require oxygen to function properly.