The results are published today in The New England Journal of Medicine.
“We show for the first time that surgery against obesity not only leads to long-term loss of weight, it also significantly reduces mortality”, says Lars Sjöström, professor emeritus at the Sahlgrenska Academy, located in Göteborg in Sweden.

Over 4,000 severely obese patients were included in the study, which Lars Sjöström started as long ago as 1987. Half of these patients underwent stomach surgery (bariatric surgery) intended to give weight loss. The remaining patients received advice concerning changes in lifestyle, also intended to give weight loss. Some of these patients also received medicines for weight loss, but even so, the conventional treatment was considerably less effective than the surgical procedure.
“The group receiving conventional treatment had even increased somewhat in weight after 10 years, while patients who had undergone surgery decreased in weight by 16%, on average. Bariatric surgery is the only treatment for severe obesity for which there is scientific evidence that it reduces mortality”, says Lena Carlsson, professor at the Sahlgrenska Academy.

A long-term follow up for between 5 and 18 years of the patients who had undergone surgery showed that mortality among these patients was 29% lower than it was among the other patients.
“The mechanisms behind the lower mortality are not clear. It seems that the reduction in risk depends less upon the actual loss of weight itself than on the fact that the patients have undergone surgery against obesity. This observation opens new possibilities for discovering previously unknown mechanisms behind the increase in risk associated with obesity, and thus opens the possibility of developing new treatments”, says Lars Sjöström.

The researchers also considered the effects of many biochemical and other variables in the analysis, including smoking, stress and previous medical history.

Journal: The New England Journal of Medicine
Article title: Effects of Bariatric Surgery on Mortality in Swedish Obese Subjects
Authors: Lars Sjöström, Kristina Narbro, David Sjöström, Kristjan Karason, Bo Larsson, Hans Wedel, Ted Lystig, Marianne Sullivan, Claude Bouchard, Björn Carlsson, Calle Bengtsson, Sven Dahlgren, Anders Gummesson, Peter Jacobson, Jan Karlsson, Anna-Karin Lindroos, Hans Lönroth, Ingmar Näslund, Torsten Olbers, Kaj Stenlöf, Jarl Torgerson, Göran Ågren and Lena M.S. Carlsson.

For more information, contact:
Professor emeritus Lars Sjöström, telephone: +46 70 677 8289, e-mail:
Professor Lena Carlsson, telephone: +46 70 679 1154, e-mail: