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Long-term Study of Bariatric Surgery for Obesity: LABS


The NIDDK funded the Longitudinal Assessment of Bariatric Surgery (LABS) observational study to research the risks and benefits of certain types of weight-loss (bariatric) surgery in adults—including gastric band and open or laparoscopic gastric bypass—and its impact on the health and well-being of people who have obesity with a body mass index (BMI) of 35 or higher. LABS played a major role in shaping clinical recommendations by identifying the types of people who are most likely to benefit from bariatric surgery. Data from the LABS study also helped the research community advance research and helped clinicians and patients understand the long-term risks and benefits of bariatric surgery.

More than 40 percent of U.S. adults have obesity and more than 9 percent have severe obesity,1 which may raise the risk of developing certain health problems such as type 2 diabetes, heart disease, liver disease, and kidney disease. People can lower their risk of developing these health problems through weight loss. However, some people, especially people who have severe obesity, may have a hard time losing weight or keeping weight off over the long term with diet and exercise alone, and they may benefit from bariatric surgery.

Over the years, bariatric surgery has become less invasive, safer, and more common. More than 250,000 bariatric surgery operations were performed in the United States in 2018, according to the American Society for Metabolic and Bariatric Surgery, or ASMBS.2 However, the surgery still involves risks.


Thirty days after bariatric surgery, LABS researchers found that

  • Death rates were low. Only 2.1 percent of participants who had open gastric bypass and 0.2 percent of participants who had laparoscopic gastric bypass died. No participants who had gastric band surgery died.
  • Only 4.1 percent of participants had at least one major bad outcome, such as death, development of blood clots, repeat surgeries, or failure to be released from the hospital.
  • No significant differences in complication risk were found based on the type of gastric bypass procedure.
  • Participants with the highest BMI values had the greatest risk of complications.
  • Participants with a history of deep vein blood clots or sleep apnea had a higher risk of complications.

At the 7-year follow-up, LABS researchers found that

  • Participants lost an average of 28.4 percent of their body weight after gastric bypass surgery and 14.9 percent of their body weight after laparoscopic gastric band surgery.
  • Most participants maintained their weight loss. Three to 7 years after surgery, participants who had gastric bypass surgery regained an average of 3.9 percent of their body weight, and participants who had gastric band surgery regained on average of 1.4 percent of their body weight.
  • High cholesterol was less common after gastric bypass and gastric band surgery.
  • Diabetes and high blood pressure were less common after gastric bypass surgery. Over time, diabetes reoccurred in some patients, but numbers of new cases were low.
  • Alcohol use disorders increased after gastric bypass surgery but not after gastric band surgery.
  • Pain and physical function improved after bariatric surgery.

Although gastric sleeve is now the most common type of bariatric surgery, it was less common when the LABS study took place. Outcomes for gastric sleeve surgeries are not included in the results.

Study Size, Participant Demographics, and Study Design

LABS started in 2003. During the first 18 months of the study, LABS researchers developed a database at the University of Pittsburgh to collect standardized information from participants. Between 2005 and 2009, LABS participants had bariatric surgery at six participating clinical centers

  • Columbia University, New York
  • East Carolina University, North Carolina
  • Oregon Health & Science University, Oregon
  • University of North Dakota, North Dakota
  • University of Pittsburgh, Pennsylvania
  • University of Washington, Washington

LABS was divided into three parts: LABS 1, LABS 2, and LABS 3.


LABS 1 looked at the short-term safety of bariatric surgery. Researchers followed 4,776 participants with an average BMI of 46.5 who had bariatric surgery between 2005 and 2007. Researchers measured complications and death rates within 30 days after surgery.


LABS 2 looked at the long-term safety and effectiveness of bariatric surgery. Researchers followed more than 2,400 people who had bariatric surgery between 2006 and 2009. Researchers collected detailed data about the surgical procedure and the care provided before and after surgery. In addition, they measured changes in the patient’s clinical, metabolic, and psychosocial characteristics, and the patient’s use of health care services following surgery. Researchers met with participants before surgery, at 6 months after surgery, at 1 year after surgery, and then annually through 2015.


LABS 3 looked more closely into specific effects of bariatric surgery. Researchers followed some LABS 1 and 2 participants through two follow-up studies.

  • Diabetes study. Researchers followed 63 participants who had type 2 diabetes to see how bariatric surgery affected their blood sugar levels.
  • Psychosocial study. Researchers followed up with 202 participants to see how bariatric surgery affected their mental well-being and eating behaviors.

Researchers met with participants one time per year.

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Last Reviewed May 2023
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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. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.