Causes

Taking in more calories than you burn can lead to obesity because the body stores unused calories as fat. Obesity can be caused by:

• Eating more food than your body can use
• Drinking too much alcohol
• Not getting enough exercise

Many obese people who lose large amounts of weight and gain it back think it is their fault. They blame themselves for not having the willpower to keep the weight off. Many people regain more weight than they lost.

Today, we know that biology is a big reason why some people cannot keep the weight off. Some people who live in the same place and eat the same foods become obese, while others do not. Our bodies have a complex system to help keep our weight at a healthy level. In some people, this system does not work normally.

Other factors that affect weight include:

• The way we eat when we are children can affect the way we eat as adults. The way we eat over many years becomes a habit. It affects what we eat, when we eat, and how much we eat.
• We are surrounded by things that make it easy to overeat and hard to stay active:
  • Many people do not have time to plan and make healthy meals.
  • More people today work desk jobs compared to more active jobs in the past.
  • People with less free time have less time to exercise.

The term "eating disorder" means a group of medical conditions that have an unhealthy focus on eating, dieting, losing or gaining weight, and body image. A person may be obese, follow an unhealthy diet, and have an eating disorder all at the same time.

Sometimes, medical problems or treatments cause weight gain, including:

• Underactive thyroid gland (hypothyroidism)
• Medicines such as birth control pills, antidepressants, and antipsychotics

Other things that can cause weight gain are:

• Quitting smoking. Most people who quit smoking gain 4 - 10 pounds in the first 6 months after quitting. Some people gain as much as 25 - 30 pounds.
• Stress, anxiety, feeling sad, or not sleeping well
• For women:
  • Menopause -- women may gain 12-15 pounds during menopause
  • Not losing the weight they gained during pregnancy

Exams and Tests

The health care provider will perform a physical exam and ask questions about your medical history, eating habits, and exercise routine.

The two most common ways to measure health risks from your weight are:

• Body mass index (BMI)
• Waist circumference (your waist measurement in inches)

BMI is measured using height and weight. You and your health care provider can use your BMI to estimate how much body fat you have.

Your waist measurement is another way to estimate how much body fat you have. Extra weight around your middle or stomach area increases your risk for type 2 diabetes, heart disease, and stroke. People with "apple-shaped" bodies (meaning their waist is bigger than their hips) also have an increased risk for these diseases.

Skin fold measurements may be taken to check your body fat percentage.

Blood tests may be done to look for thyroid or hormone problems that could lead to weight gain.

Treatment

CHANGING YOUR LIFESTYLE

An active lifestyle and regular exercise, along with healthy eating, is the best way to lose weight. Even modest weight loss can improve your health. You will need a lot of support from family and friends.

When dieting, your main goal should be to learn new, healthy ways of eating and make them a part of your daily routine.

Many people find it hard to change their eating habits and behaviors. You may have practiced some habits for so long that you may not even know they are unhealthy, or you do them without thinking. You need to be motivated to make lifestyle changes. Make the behavior change part of your life over the long term. Know that it takes time to make and keep a change in your lifestyle.

Work with your health care provider and dietitian to set realistic, safe daily calorie counts that help you lose weight while staying healthy. Remember that if you drop pounds slowly and steadily, you are more likely to keep them off. Your dietitian can teach you about:

• Healthy food choices
• Healthy snacks
• Sweetened drinks
• Portion sizes
• How to read the nutrition labels
• New ways to prepare food

Extreme diets (fewer than 1,100 calories per day) are not thought to be safe or to work very well. These types of diets often do not contain enough vitamins and minerals. Most people who lose weight this way return to overeating and become obese again.

Learn new ways to manage stress, rather than snacking. Examples may be meditation, yoga, or exercise. If you are depressed or stressed a lot, talk to your health care provider.

MEDICATIONS AND HERBAL REMEDIES

You may see ads for supplements and herbal remedies that claim they will help you lose weight. Many of these claims are not true, and some of these supplements can have serious side effects. Talk to your health care provider before using them.

Several prescription weight loss drugs are available. Most people lose between 5 and 10 pounds by taking these drugs. Most people also regain the weight when they stop taking the medicine, unless they have made lasting lifestyle changes, such as exercising and cutting unhealthy foods from their diet.

SURGERY

Bariatric surgery can reduce the risk of disease in people with severe obesity. These risks include:

• Arthritis
• Diabetes
• Heart disease
• High blood pressure
• Sleep apnea
• Some cancers
• Stroke

Surgery may help people who have been very obese for 5 years or more and have not lost weight from other treatments, such as diet, exercise, or medicine.

Surgery alone is not the answer for weight loss. It can train you to eat less, but you still have to do much of the work. You must be committed to diet and exercise after the surgery. Talk to your doctor to learn if this is a good option for you.

The two most common weight-loss surgeries are:

• Laparoscopic gastric banding
• Gastric bypass surgery

You may have complications from these surgeries. One problem some people have is throwing up if they eat more than their new small stomach can hold.

Support Groups

Many people find it easier to follow a diet and exercise program if they join a group of people with similar problems.

See: Eating disorders - support group

Possible Complications

Obesity is a major health threat. The extra weight puts added stress on every part of your body.

People with obesity are at risk for these health problems:

• Bone and joint problems -- extra weight puts strain on the bones and joints. This can lead toosteoarthritis, a disease that causes joint pain and stiffness.
• Gallstones and liver problems
• Heart attack from coronary heart disease, congestive heart failure, and stroke
• High blood cholesterol and triglycerides (dislipidemia or high blood fats)
• High blood pressure (hypertension)
• High blood sugar (glucose) or diabetes
• Stopping breathing during sleep (sleep apnea). This can cause daytime fatigue or sleepiness, poor attention, and problems at work.

Alternative Names

Morbid obesity; Fat - obese

References

Garb J, Welch G, Zagarins S, Kuhn J, Romanelli J. Bariatric surgery for the treatment of morbid obesity: a meta-analysis of weight loss outcomes for laparoscopic adjustable gastric banding an dlaparoscopic gastric bypass. Obes Surg. 2009;19:1447-1455.

Sacks FM, Bray GA, Carey VJ, Smith SR, Ryan DH, Anton SD, et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N Engl J Med. 2009;360:859-873.

Dale KS, McAuley KA, Taylor RW, Williams SM, Farmer VL, Hansen P, et al. Determining optimal approaches for weight maintenance: a randomized controlled trial. CMAJ. 2009;180:E39-E46.

United States Department of Agriculture. Dietary Guidelines for Americans, 2010. Accessed June 5, 2011.

Richards WO, Schirmer BD. Morbid obesity. In: Townsend CM Jr., Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 17.

Seagle HM, Strain GW, Makris A, Reeves RS; American Dietetic Association. Position of the American Dietetic Association: weight management. J Am Diet Assoc. 2009;109:330-346.

Svetke LP, Stevens VJ, Brantley PJ, et al. Comparison of strategies for sustaining weight loss: the weight loss maintenance randomized controlled trial. JAMA. 2008;299:1139-1148.

Kaplan LM, Klein S, Boden G, et al. Report of the American Gastroenterological Association (AGA) Institute Obesity Task Force. Gastroenterology. 2007;132:2272-2275.

Update Date: 4/11/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.