Obesity is a term used to describe body weight that is much greater than what is considered healthy. There are many ways to determine if a person is obese, but experts believe that a person's body mass index (BMI) is the most accurate measurement of body fat for children and adults.

Adults with a BMI greater than 30 are considered obese. Adults with a BMI between 25 and 29.9 are considered overweight. There are exceptions. For example, an athlete may have a higher BMI but not be overweight.

Nearly two-thirds of the United States population is overweight. Anyone more than 100 pounds overweight is considered morbidly obese.

Rates of obesity are climbing. The percentage of children who are overweight has doubled in the last 20 years. The percentage of adolescents who are obese has tripled in the last 20 years.

Consuming more calories than you burn leads to being overweight and, eventually, obesity. The body stores unused calories as fat. Work with your health care provider to determine how many calories you need to consume each day to stay healthy.

Obesity increases a person's risk of illness and death due to diabetes, stroke, heart disease, high blood pressure, high cholesterol, and kidney and gallbladder disease. Obesity may increase the risk for some types of cancer. It is also a risk factor for the development of osteoarthritis and sleep apnea.

Genetic factors play some part in the development of obesity -- children of obese parents are 10 times more likely to be obese than children with parents of normal weight.

• Consumption of more food than the body can use
• Excess alcohol intake
• Sedentary lifestyle

Tips for preventing weight gain: 

• Avoid foods that are high in fat and sugar.
• Reduce how much alcohol you drink.
• Avoid stress, frustration, and boredom.
• If you are depressed, seek medical treatment.

Avoid a sedentary lifestyle by increasing your activity level:

• Perform aerobic exercise for at least 30 minutes a day, 3 times a week .
• Increase physical activity by walking rather than driving.
• Climb stairs rather than using an elevator or escalator.
• Always talk to your health care provider before starting an exercise program.

For additional help in losing weight:

• Join a support group (see eating disorders - support group). Many people find it easier to follow a diet and exercise program if they join a group of people with similar problems.
• Be sure to set realistic goals for weight loss. A loss of 1 to 2.5 pounds a week may seem slow, but losing weight too fast often does not work. Weight lost quickly usually comes back quickly.

See: Losing weight

• You are unable to lose weight on your own.

The health care provider will perform a physical exam and ask questions about your medical history. Questions may include:

• Time pattern
  • Has you always tended to be heavy?  
  • Is this recent weight gain? 
• Eating habits
  • Have you changed your diet?
  • Have your eating habits changed?
  • What percent of the daily calories are from fat?
  • How many meals do you eat in a day? What type of foods?
  • How many snacks do you eat in a day? What type of snacks?
• Exercise habits
  • Has your activity level changed?
  • Has there been a decrease in your daily activity?
• Other factors
  • Have you had an increase in emotional stress?
  • Are you drinking more alcohol? 
  • What other symptoms are occurring at the same time?

Skin fold measurements may be taken to assess body composition. Blood studies to test endocrine function may be performed.

Treatment:

Even modest weight loss can improve your health. It is important to work with your health care provider or dietician to develop a plan that is best for you. For most people, weight can be lost by eating a healthier diet, exercising more, and adopting new behaviors such as keeping a food diary, avoiding food triggers, and thinking positively.

See: Weight management and Exercise and weight loss.

Prescription weight loss drugs are an option for some people. The two main ones are subutramine (Meridia) and orlistat (Xenical). Ask your health care provider if these are right for you.

There are many over-the-counter diet products. Most do not work and some can be dangerous. Before using one, talk to your health care provider.

Surgery may be an option for those people who are significantly obese (BMI over 35) who can not lose weight using other methods. Weight loss surgery can significantly improve weight and health in the right candidate. Talk to your doctor to learn if this is a good option for you.

See: Gastric bypass surgery