SOS study: surgery effective against early-onset obesity

Bariatric surgery is effective for individuals who develop obesity by the age of 20, as for those who have developed obesity later in life, according to a study from the University of Gothenburg. The results are based on data from the Swedish Obese Subjects (SOS) study. Started in 1987, this study is led and coordinated from Sahlgrenska Academy at the University of Gothenburg.


The present sub-study covers a total of 4,026 adult individuals who had developed obesity. Half of them had undergone bariatric surgery and the other half were a control group. Each of the groups was divided into three subgroups, based on the participants' BMI at age 20: those of normal weight, those who were overweight and those with obesity.

The researchers then investigated whether there was any difference in the effects of bariatric treatment for obesity among those who had developed the disorder before age 20, compared with those who developed it later in life. The results were revealed in the paper, ‘Effects of Bariatric Surgery in Early- and Adult-Onset Obesity in the Prospective Controlled Swedish Obese Subjects Study’, published in Diabetes Care.

"We were somewhat surprised at the results. Since the group that had already developed obesity by the age of 20 had been exposed to obesity and its risks for longer periods, we'd expected that bariatric surgical treatment in these participants would be less effective in terms of weight loss and obesity-related sequelae than in the other group. But it wasn't like that," said Dr Johanna Andersson Assarsson, researcher and study coordinator for SOS, and one of the study's co-authors. "On the contrary, the group with obesity at age 20 lost a little bit more weight after the operation, and there was no difference in effects on diabetes or its complications, cardiovascular disease or cancer, compared with individuals who developed obesity later in life."

There were small but statistically significant differences in reduction of body weight among the subgroups after bariatric surgery (p=0.032), with the largest reductions among those with obesity aged 20 years. Bariatric surgery increased type 2 diabetes remission (odds ratios 4.51, 4.90, and 5.58 in subgroups with normal BMI, overweight, or obesity at 20 years of age, respectively; p=0.951), reduced type 2 diabetes incidence (odds ratios 0.15, 0.13, and 0.15, respectively; p=0.972) and reduced microvascular complications independent of obesity status at 20 years of age (p=0.650). The association between bariatric surgery and cardiovascular disease was similar in the subgroups (p=0.674). Surgical complications were similar in the subgroups.

For many diseases, early treatment is advantageous, but individuals with early-onset obesity have often had their disorder for a long time before bariatric surgery is considered. It has sometimes been speculated that bariatric surgical treatment would be less effective in these individuals because of their longer exposure to the adverse health effects of obesity.

"Here, we show that's not the case. And we think it's important that this information reaches people considering bariatric surgery for obesity and also health professionals who treat patients with obesity," she added.