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Causes

By Mayo Clinic staff

Although there are genetic and hormonal influences on body weight, the bottom line is that obesity occurs when you take in more calories than you burn through exercise and normal daily activities. Your body stores these excess calories as fat. Obesity usually results from a combination of causes and contributing factors, including:

  • Inactivity. If you're not very active, you don't burn as many calories. Unfortunately, today most adults spend most of their day sitting, whether at home, at work or during leisure activities. With a sedentary lifestyle, you can easily take in more calories every day than you burn off through exercise or normal daily activities. Watching too much television is one of the biggest contributors to a sedentary lifestyle and weight gain.
  • Unhealthy diet and eating habits. Having a diet that's high in calories, eating fast food, skipping breakfast, eating most of your calories at night, consuming high-calorie drinks and eating oversized portions all contribute to weight gain.
  • Pregnancy. During pregnancy a woman's weight necessarily increases. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.
  • Lack of sleep. Getting less than seven hours of sleep a night can cause changes in hormones that increase your appetite. You may also crave foods high in calories and carbohydrates, which can contribute to weight gain.
  • Certain medications. Some medications can lead to weight gain if you don't compensate through diet or activity. These medications include some antidepressants, anti-seizure medications, diabetes medications, antipsychotic medications, steroids and beta blockers.
  • Medical problems. Obesity can sometimes be traced to a medical cause, such as Prader-Willi syndrome, Cushing's syndrome, polycystic ovary syndrome, and other diseases and conditions. Some medical problems, such as arthritis, can lead to decreased activity, which may result in weight gain. A low metabolism is unlikely to cause obesity, as is having low thyroid function.
Risk factors Symptoms
References
  1. Defining overweight and obesity. Centers for Disease Control & Prevention. http://www.cdc.gov/nccdphp/dnpa/obesity/defining.htm. Accessed Jan. 26, 2009.
  2. Ogden CL, et al. Obesity among adults in the United States - No statistically significant change since 2003-2004. NCHS data brief no 1. Hyattsville, MD: National Center for Health Statistics. 2007.
  3. Still CD, et al. Obesity. In: Rakel & Bope: Conn's Current Therapy. 60th ed. Philadelphia: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/117958748-3/0/1621/295.html#4-u1.0-B978-1. Accessed Feb. 20, 2009.
  4. Bray GA. Etiology and natural history of obesity. http://www.uptodate.com/home/index.html. Accessed Jan. 26, 2009.
  5. Kushner RF. Obesity management. Gastroenterology Clinics of North America. 2007;36:191.
  6. Duval K, et al. Health-related quality of life in morbid obesity. Obesity Surgery. 2006;16:574.
  7. Hainer V, et al. Treatment modalities of obesity: What fits whom? Diabetes Care. 2008;31(suppl 2):S269.
  8. Understanding adult obesity. National Institute of Diabetes and Digestive and Kidney Diseases. http://www.win.niddk.nih.gov/publications/understanding.htm. Accessed Jan. 26, 2009.
  9. Bessesen DH. Update on obesity. Journal of Clinical Endocrinology and Metabolism. 2008;93:2027.
  10. Bray GA. Overview of therapy for obesity in adults. http://www.uptodate.com/home/index.html. Accessed Jan. 26, 2009.
  11. Svetkey LP, et al. Comparison of strategies for sustaining weight loss: The Weight Loss Maintenance Randomized Controlled Trial. JAMA. 2008;299:1139.
  12. The practical guide: Identification, evaluation, and treatment of overweight and obesity in adults. National Institutes of Health, U.S. Department of Health and Human Services. http://www.nhlbi.nih.gov/guidelines/obesity/prctgd_c.pdf. Accessed Feb. 25, 2009.
  13. Donnelly JE, et al. American College of Sports Medicine position stand: Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Medicine & Science in Sports & Exercise. 2009;41:459.
  14. Sacks F, et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. New England Journal of Medicine. 2009;360:859.
  15. Mun EC, et al. Surgical management of obesity. http://www.uptodate.com/home/index.html. Accessed Feb. 26, 2009.
  16. Hensrud DD (expert opinion). Mayo Clinic, Rochester, Minn. April 2, 2009.
  17. Anderson CA (expert opinion). Mayo Clinic, Rochester, Minn. March 3, 2009.

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May 9, 2009

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