Losing Weight and Losing FatYour weight is determined by the rate at which you store energy from the food that you eat, and the rate at which you use that energy. Remember that as your body breaks down fat, the number of fat cells remains the same; each fat cell simply gets smaller.
Most experts agree that the way to maintain a healthy weight is:

• Eat a balanced diet - appropriate amounts of carbohydrates, fat and protein
• Do not eat excessively - for most people, a diet of 1,500 to 2,000 calories a day is sufficient to maintain a healthy weight
• Exercise regularly

In the fat cell, other types of lipases work to break down fats into fatty acids and glycerol. These lipases are activated by various hormones, such as glucagon, epinephrine and growth hormone. The resulting glycerol and fatty acids are released into the blood, and travel to the liver through the bloodstream. Once in the liver, the glycerol and fatty acids can be either further broken down or used to make glucose.
When you are not eating, your body is not absorbing food. If your body is not absorbing food, there is little insulin in the blood. However, your body is always using energy; and if you're not absorbing food, this energy must come from internal stores of complex carbohydrates, fats and proteins. Under these conditions, various organs in your body secrete hormones:

These hormones act on cells of the liver, muscle and fat tissue, and have the opposite effects of insulin.
When you are not eating, or you are exercising, your body must draw on its internal energy stores. Your body's prime source of energy is glucose. In fact, some cells in your body, such as brain cells, can get energy only from glucose.