Definition & Facts for Bariatric Surgery

What is obesity?

Obesity is defined as having a body mass index (BMI) of 30 or more. BMI is a measure of your weight in relation to your height. Class 1 obesity means a BMI of 30 to 35, Class 2 obesity is a BMI of 35 to 40, and Class 3 obesity is a BMI of 40 or more. Classes 2 and 3, also known as severe obesity, are often hard to treat with diet and exercise alone.

Calculate your BMI to learn your BMI category.

What is bariatric surgery?

Bariatric surgery is an operation that helps you lose weight by making changes to your digestive system. Some types of bariatric surgeries make your stomach smaller, allowing you to eat and drink less at one time and making you feel full sooner. Other bariatric surgeries also change your small intestine—the part of your body that absorbs calories and nutrients from foods and beverages.

Bariatric surgery may be an option if you have severe obesity and have not been able to lose weight or keep from gaining back any weight you lost using other methods such as lifestyle treatment or medications. Bariatric surgery also may be an option if you have serious health problems, such as type 2 diabetes or sleep apnea, related to obesity. Bariatric surgery can improve many of the medical conditions linked to obesity, especially type 2 diabetes.

Does bariatric surgery always work?

Studies show that many people who have bariatric surgery lose about 15 to 30 percent of their starting weight on average, depending on the type of surgery they have. However, no method, including surgery, is sure to produce and maintain weight loss. Some people who have bariatric surgery may not lose as much as they hoped. Over time, some people regain a portion of the weight they lost. The amount of weight people regain may vary. Factors that affect weight regain may include a person’s level of obesity and the type of surgery he or she had.

Bariatric surgery does not replace healthy habits, but may make it easier for you to consume fewer calories and be more physically active. Choosing healthy foods and beverages before and after the surgery may help you lose more weight and keep it off long term. Regular physical activity after surgery also helps keep the weight off. To improve your health, you must commit to a lifetime of healthy lifestyle habits and following the advice of your health care providers.

Three ladies exercising
Maintaining healthy lifestyle habits may help
you succeed after bariatric surgery.

How much does bariatric surgery cost?

On average, bariatric surgery costs between $15,000 and $25,000, depending on what type of surgery you have and whether you have surgery-related problems. Costs may be higher or lower based on where you live. The amount your medical insurance will pay varies by state and insurance provider.

Medicare and some Medicaid programs cover three common types of bariatric surgery—gastric bypass, gastric band, and gastric sleeve surgery—if you meet certain criteria and have a doctor’s recommendation. Some insurance plans may require you to use approved surgeons and facilities. Some insurers also require you to show that you were unable to lose weight by completing a nonsurgical weight-loss program or that you meet other requirements.

Your health insurance company or your regional Medicare or Medicaid office will have more information about bariatric surgery coverage, options, and requirements.

July 2016
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Anita Courcoulas, M.D., M.P.H, University of Pittsburgh School of Medicine; Walter J. Pories, M.D., F.A.C.S., Brody School of Medicine, East Carolina University