Obesity


Definition

Obesity means having too much body fat. It is not the same as being overweight, which means weighing too much. A person may be overweight from extra muscle, bone, or water, as well as from having too much fat.

Both terms mean that a person's weight is higher than what is thought to be healthy for his or her height.


Alternative Names

Morbid obesity; Fat - obese


Causes, incidence, and risk factors

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

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.


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Review Date: 7/11/2011
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.
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