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Causes

By Mayo Clinic staff

Although there are genetic and hormonal influences on body weight, 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. With a sedentary lifestyle, you can easily take in more calories every day than you use through exercise and normal daily activities.
  • 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, drinking high-calorie beverages 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/obesity/defining.html. Accessed Feb. 14, 2011.
  2. Still CD, et al. Obesity. In: Rakel & Bope: Conn's Current Therapy. 60th ed. Philadelphia, Pa.: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/117958748-3/0/1621/295.html#4-u1.0-B978-1. Accessed Feb. 15, 2011.
  3. Bray GA. Etiology and natural history of obesity. http://www.uptodate.com/home/index.html. Accessed Feb. 16, 2011.
  4. Kushner RF. Obesity management. Gastroenterology Clinics of North America. 2007;36:191.
  5. Duval K, et al. Health-related quality of life in morbid obesity. Obesity Surgery. 2006;16:574.
  6. Hainer V, et al. Treatment modalities of obesity: What fits whom? Diabetes Care. 2008;31(suppl 2):S269.
  7. Understanding adult obesity. National Institute of Diabetes and Digestive and Kidney Diseases. http://www.win.niddk.nih.gov/publications/understanding.htm. Accessed Feb. 15, 2011.
  8. Bray GA. Overview of therapy for obesity in adults. http://www.uptodate.com/home/index.html. Accessed Feb. 16, 2011.
  9. Svetkey LP, et al. Comparison of strategies for sustaining weight loss: The Weight Loss Maintenance Randomized Controlled Trial. Journal of the American Medical Association. 2008;299:1139.
  10. The practical guide: Identification, evaluation, and treatment of overweight and obesity in adults. U.S. Department of Health and Human Services. http://www.nhlbi.nih.gov/guidelines/obesity/prctgd_c.pdf. Accessed Feb. 15, 2011.
  11. 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.
  12. 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.
  13. Jones D, et al. Surgical management of severe obesity. http://www.uptodate.com/home/index.html. Accessed Feb. 16, 2011.
  14. Meridia (sibutramine): Market withdrawal due to risk of serious cardiovascular events. U.S. Food and Drug Administration. http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm228830.htm. Accessed Oct. 8, 2010.
  15. Najm W, et al. Herbals used for diabetes, obesity, and metabolic syndrome. Primary Care. 2010;37:237.
  16. Cho SH, et al. Acupuncture for obesity: A systematic review and meta-analysis. International Journal of Obesity. 2009;33:183.
  17. Completed safety review: Xenical/Alli (Orlistat) and severe liver injury. U.S. Food and Drug Administration. http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm213038.htm. Accessed Feb. 16, 2011.
DS00314 May 6, 2011

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