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Blacks lose less weight after gastric bypass, but diabetes may offset the difference

NEW YORK (Reuters Health) – Two separate long-term studies show that blacks, men, and older people may lose less weight after gastric bypass surgery.

Black women with type 2 diabetes do tend to lose the usual amount of weight, according to one of the reports.

“This was a very surprising finding because we know from past studies that adding diabetes is a bad factor for weight loss, essentially they lose less,” said lead investigator Dr. Alfonso Torquati, director of the Duke Center for Metabolic and Weight Loss Surgery at Duke University in Durham, North Carolina, in an interview.

In the female Caucasian group, those with diabetes did worse, but the female African-Americans lose weight similarly to the Caucasian women without diabetes, Dr. Torquati said.

Dr. Torquati presented his research June 20th at the annual meeting of the American Society for Metabolic & Bariatric Surgery in San Diego, California.

His team studied 78 black women who underwent laparoscopic Roux-en-Y gastric bypass surgery in a nested, case-controlled study, matching them to 204 white female patients with similar ages, body mass index (BMI), and prevalences of hypertension and sleep apnea.

At every point in the three-year study period, the black women overall had significantly less weight loss than the white women (p<0.001).

“Three years out, we saw close to 8% difference between the two groups,” Dr. Torquati said.

On multivariate analysis, diabetes appeared to predict greater weight loss among black patients — and less among white patients. No other variable tested had a significant effect.

The researchers are not sure why, however.

“We have a few hypotheses. We’re now looking at some genetic factors that could play a role in this,” Dr. Torquati says.

The second study, also presented at the San Diego conference, appears to confirm that black race may predict less weight loss, as can older age and male gender.

Dr. Ramsey Dallal, at Einstein Healthcare Network in Philadelphia, followed 1,096 gastric bypass patients for an average of two years.

On average, the African American patients in the study lost 63.2% of their excess weight, while Caucasians lost 71.9%. Men lost 63% and women lost 71%.

Race, sex and age were independent predictors of weight loss.

The researchers calculated the odds that a patient would be one of the 232 individuals in the lower 25th percentile of weight loss, i.e., having lost no more than 57.4% of their excess weight.

Logistic regression showed that the patients more likely to be in that least successful group were black (odds ratio: 2.8, p=0.001), older (OR: 0.967, p=0.001), male (OR: 0.302, p<0.0005), and heavier at baseline (OR: 0.861 p<0.0005).

The results do not suggest that black people or older men will not benefit from gastric bypass, Dr. Dallal said. In fact, all of the patients lost weight. The new findings do help predict how much weight a patient is likely to lose, however, according to Dr. Dallal.

Experts who commented on the studies agreed that generally, the findings of both studies can help doctors inform their patients.

“We know that obesity affects minorities unequally, so shedding more light and getting more data on people in those groups, and using that to manage their expectations is very important,” said Dr. Robin Blackstone, director of Scottsdale Bariatric Center in Scottsdale, Arizona and President of the American Society for Metabolic & Bariatric Surgery.

“It also tells us that there may be something about obesity in those populations that is different,” Dr. Blackstone said.

“That’s what’s interesting about what we do,” Dr. Dallal said, “You answer some questions and you’re left with other questions to answer.”