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Last full review/revision Dec 2019| Content last modified Dec 2019
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What is obesity?

Obesity is having too much body fat. Obesity causes health problems. The fatter you are, the higher your risk of health problems.

  • Obesity is caused by eating more calories than your body needs

  • Being obese increases your chances of getting many diseases, such as diabetes, high blood pressure, heart disease, and certain cancers

  • Losing even a little weight can lessen your chances of having health problems

  • To lose weight, you should eat less and be more active (get exercise)

  • Medicine or surgery can sometimes help with weight loss

Obesity can cause problems in almost any organ.

Obesity is more and more common throughout the world. In the United States, about 1 in 3 adults is obese. Obesity in childhood is also a problem.

What causes obesity?

Obesity is caused by taking in more calories than your body needs. Diet, genes, lifestyle, and use of certain drugs are some factors in obesity.

The following increase your chance of being obese:

  • Not getting enough physical activity, such as through sports or workouts, or having a job where you sit most of the time

  • Eating high-calorie foods (for example, from vending machines or fast food restaurants) or eating too much food for a long period of time

  • Having family members who are obese (obesity runs in families)

  • Having been obese as a child

  • Not losing pregnancy weight after having children

  • Hormonal changes such as menopause (when a woman stops having periods and can no longer get pregnant)

  • Having certain eating disorders, such as binge eating disorder

  • Taking certain medicines

  • Sleeping less than 6 hours a night

  • Changes in the normal germs (bacteria) in the intestines—research about this is new, so not much is known or understood about it

What are the symptoms of obesity?

Obesity may cause symptoms besides looking overweight. You may have:

  • Trouble breathing

  • Snoring

  • Skin problems including stretch marks

  • Joint and back pain

How can doctors tell if I am obese?

Doctors can tell if you're obese by:

  • Calculating your BMI (body mass index)

  • Measuring how thick the fat is on your waist and on the back of your upper arm

  • Sometimes doing a test that measures how much fat is in your whole body (body composition test)

Your BMI is your weight (in kilograms) divided by your height (in meters). You're obese if your BMI is 30 or higher. You're overweight if your BMI is over 25.

Doctors may also:

How do doctors treat obesity?

Obesity is much easier to prevent than treat. Once you gain weight, your body resists losing weight. For example, when you go on a diet, you feel hungrier and burn less energy when you’re resting.

Doctors treat obesity by helping you change some of your habits:

  • Eat healthier foods (high in fiber, low in sugar)

  • Put smaller portions on your plate so you're not tempted to eat as much

  • Eliminate high-calorie drinks, such as soda, juice, or alcohol

  • Exercise more and be more active (for example, take the stairs instead of the elevator, or walk instead of driving or taking the bus)

Going to group meetings with other people trying to lose or control their weight may help you keep your healthy eating and exercise habits on track.

For people with a lot of weight to lose, doctors may offer:

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