Preventing obesity is important. Once fat cells form, they remain in your body forever. Although you can reduce the size of fat cells, you cannot get rid of them. Obesity experts recommend that a key to preventing excess weight gain is monitoring fat consumption instead of counting calories, and therefore the National cholesterol Education Program maintains that only 30 % of calories should be derived from fat. Only one-third of those calories should be contained in saturated fats (the reasonably fat found in high concentrations in meat, poultry, and dairy farm products).Because most people eat more than they think they do, keeping a detailed food diary is a useful way to assess eating habits.