For most people, the term obesity means to be very overweight. Others use the words obese and overweight synonymously. But they are not synonyms. Most health professionals define overweight as an excess amount of body weight that includes muscle, bone, fat, and water. Obesity specifically refers to an excess amount of body fat.    The term 'obese' or 'obesity' should actually be reserved for a very specific situation, and that is to describe a people who are at definite clinical risk because of the excess amount of body fat that they have. For men, this is considered to occur when their body fat exceeds 20% of their total weight. For women, they are defined as obese - and

at clinical risk - when their body fat exceeds 30% of their total weight.    Being overweight does not put the person at clinical or medical risk, but being obese does. Being overweight simply indicates that the person weighs more than some generally acceptable standard says he or she should. Unfortunately, the height-weight charts do not provide as sophisticated a method of determining clinical risk as we need. People with large body frame, wrestlers, bodybuilders or other athletes with a lot of muscle, can be overweight without being obese. For many such people, the addition of a healthy, metabolically active amount of muscle actually makes it appear on the height-weight charts as if they weigh too much.     Obesity happens when a person consumes more calories than he/she burns. Reasons for this imbalance include genetic, environmental, psychological, and other factors.    1. Genetic Factors - Obesity tends to run in families, suggesting a genetic cause. Yet families also share diet and lifestyle habits that may contribute to obesity. Separating these from genetic factors is often difficult. Even so, science shows that heredity is linked to obesity.    2. Environmental Factors - Environment may also strongly influence obesity. This includes lifestyle habits such as diet and level of physical activity. The American culture tends to eat high-fat foods, and put taste and convenience ahead of nutrition. And, most Americans do not get enough physical activity. Learning about nutrition concepts and how your body responds to different kinds of diets and exercise goes a long way in putting you on track to a healthier body.    3. Psychological Factors - Many people eat in response to negative emotions such as boredom, sadness, or anger. Most overweight people have no more psychological problems than people of average weight. However, up to 10% of the mildly obese people trying to lose weight have binge eating disorder. This disorder is even more common in people who are severely obese. During a binge eating episode, people feel they cannot control how much they are eating and eat large amounts of food. Those with the most severe binge eating problems are also likely to have symptoms of depression and low self-esteem. These people may have more difficulty losing weight and keeping it off than people without binge eating problems.    4. Other Factors - Some illnesses can lead to obesity or a tendency to gain weight: hypothyroidism, Cushing's syndrome, depression, and certain neurological problems. Drugs, such as steroids and some antidepressants may also cause weight gain.