One Size Doesn't Fit All: Surgery Benefits Vary by Obese Subtype

Miriam E. Tucker

November 16, 2018

NASHVILLE, Tennessee — Bariatric surgery may be most beneficial for people with disordered eating, whereas those with extreme obesity that starts early in life may experience a bit less weight loss after such a procedure, new research suggests.

The findings, from the Longitudinal Assessment of Bariatric Surgery (LABS) consortium, comprising seven centers, were presented November 15 here at Obesity Week 2018 by Alison E. Field, ScD, chair of the Department of Epidemiology at Brown University School of Public Health, Providence, Rhode Island.

The findings were simultaneously published in Obesity.

"There probably isn't one magic bullet for obesity — if there is a magic bullet, it's going to be different for different groups of people," said Field in a press release from her institution.

Ask About Disordered Eating; Subtypes Do Make Sense

Using baseline data for 2,456 LABS patients, Field and colleagues identified four subgroups with differing weight loss outcomes at 3 years following bariatric surgery: class 1 patients had diabetes and low HDL cholesterol levels; class 2, diabetes with disordered eating; class 3, diabetes with a mix of features; and class 4, diabetes with extreme obesity of early onset.

Overall, at 3 years, those in class 2 and class 3 experienced significantly greater 3-year weight loss after surgery than did those in classes 1 and 4.

"When reviewing the literature to guide your clinical practice, look at more than the mean response. Subgroup analyses may help to identify appropriate treatment for particular subtypes of patients," Field advised in an interview with Medscape Medical News.

She said that more data are needed to determine the optimal treatment for each "obesity subtype," but until those data are available, it's a good idea to ask patients about disordered eating.

"I think it would be useful to ask patients about how often they keep eating even when they feel full and how often they eat when they are not hungry. Providers likely already collect data information on age of onset of obesity. If they do not do so already, it would be a good question to ask their patients," she said.

Asked to comment on the findings, American Society for Metabolic and Bariatric Surgery President Samer Mattar, MD, medical director of Swedish Weight Loss Services, Seattle, Washington, told Medscape, "This is a phenomenon that we recognize anecdotally. Some patients do very well, and some less so. Everybody benefits, but some benefit less than others."

Genetics likely play a major role, Mattar added, such that "patients are hardwired in ways that promote adequate response to the treatments that we deliver, and others are a little more resistant. We still don't understand most of the reasons," he noted.

"We know that there are genetic phenotypes, or subtypes. It's nice to see a study that actually takes this into consideration and researches this problem, especially one as respected and recognize as the LABS study," he said.

He cautioned, though, that the majority of patients in LABS had undergone gastric bypass, followed by gastric banding, whereas only a small number underwent sleeve gastrectomy, so "it doesn't necessarily reflect today's distribution of cases, which are majority sleeve."

Nonetheless, he noted that the four subtypes do make sense in light of his own experience.

Surgery Outcomes Differ by Subtype

In the study, there were 91 patients in classe 1, 892 in class 2, 1108 in class 3, and 365 in class 4. About two thirds of the patients in classes 1 and 4 (diabetes/low HDL and extreme obesity of early onset) were women; women made up an even greater proportion of the other two groups.

Approximately 98% of participants in class 1 had diabetes, compared with <40% in the other classes.

The median baseline body mass index (BMI) was significantly higher in class 4 than in the other groups (58.3 kg/m2), but in that group, the prevalence of diabetes was lower than in class 1 (38.5% vs 97.8%).

On the basis of interviews, high proportions of people in class 2 (disordered eating) experienced grazing with loss of control (60.8%), binge eating disorder (36.6%), night eating (26.0%), often eating when not hungry (92.4%), and eating when full (73.9%).

Those behaviors were also identified in 41.7%, 19.8%, 14.1%, 37%, and 31.7% of class 1 patients, respectively, but were much less common in classes 3 and 4.

Patients in classes 2 and 3 three benefited more from bariatric surgery than patients in classes 1 and 4.

Men and women with disordered eating (class 2) lost the most weight, at an average of 28.5% and 33.3% of presurgery weight, respectively.

Among those in class 4, men weighed an average of 25% less than baseline after 3 years; women weighed 30.3% less. Weight loss in class 1 was not significantly different from that in class 4.

Research is needed to understand whether the greater weight loss in the subgroup with disordered eating "reflects becoming less sensitive to external cues, changes in appetite, or other changes in appetitive behaviors," the researchers note in their article.

And although those in class 1 (diabetes with low HDL) did not lose as much weight as those in classes 2 and 3, this group might benefit most from the reductions in diabetes that have been consistently observed with bariatric surgery, they observe.

Mattar commented, "These findings will add to our basic knowledge. I think the message is that bariatric/metabolic surgery can positively affect all patients, but to varying degrees."

Field and her colleagues are now developing a mobile app to measure what influences individuals' eating behaviors in real time. Field hopes the app can eventually be used to provide tailored interventions. She has a beta version of the app, and hopes to move forward in fully developing and testing it.

The study was funded by the National Institute of Diabetes, Digestive, and Kidney Diseases.

Obesity Week 2018. Presented November 15, 2018.

Obesity. Published online November 13, 2018. Full text

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