From the Journals

A new weight loss threshold for T2d remission after bariatric surgery?



Patients with type 2 diabetes who underwent bariatric surgery commonly experienced remission, but there was little increase in rates of remission above a threshold of 20% total weight loss (TWL), according to a retrospective analysis of 5,928 patients with diabetes in an integrated health care system in Southern California.

Karen Coleman, PhD, professor of health systems science at Kaiser Permanente Southern California

Dr. Karen Coleman

The findings should reassure physicians and patients that surgery will be beneficial, according to lead author Karen Coleman, PhD, professor of health systems science at Kaiser Permanente Southern California.

Dr. Coleman has heard from many physicians saying they recommend against bariatric surgery because of concerns that patients gain weight back and therefore won’t get a long-term benefit, but this is not supported by the literature. “Hundreds of articles at this point show that this simply is not true. In addition, providers seem to think about bariatric surgery as an ‘all or none’ treatment. Gaining any weight back means that patients ‘fail.’ Weight regain is a normal part of massive weight loss; however, maintaining a certain amount of weight loss still provides benefits for patients, especially those with cardiovascular conditions like diabetes,” said Dr. Coleman.

Most patients lose 20%-30% of their body weight after bariatric surgery, but they don’t have to lose that much to see an improvement in type 2 diabetes (T2D). In addition, if patients lose that much or more, and then gain some weight back, it doesn’t eliminate benefit. “Although we did not measure weight regain, a corollary statement is that patients can regain some of the weight they lose, but if they stay around 20% of their total weight lost, then their diabetes still remits,” said Dr. Coleman.

In the past, some standards to treat severe weight loss and metabolic disease called for 50% or more TWL. More recent standards target a 30% threshold. “We want physicians to understand that they need to have more reasonable expectations of weight loss with surgery and that these reasonable expectations still result in profound improvements in cardiovascular risk, death, and quality of life. A 20% TWL threshold is easier for these patients to get to, and like other patients, they still get the benefit. So even if these patients may not have as much weight loss they can still benefit from the surgery for their diabetes,” Dr. Coleman added.

Physicians have long assumed that the effect of bariatric surgery on T2D remission is tied to weight loss, but this has been tested only recently. Previous studies found a link and suggested that 25% TWL may be the needed threshold, but more data are needed, especially for sleeve gastrectomy.

In the current study, published in Diabetes Care, 73% of patients were female. Mean age was 49.8 years, and mean body mass index was 43.8 kg/m2. Fifty-seven percent underwent Roux-en-Y gastric bypass (RYGB). Follow-up averaged 5.9 years. Overall, 71% of patients had an initial remission of their diabetes (72% RYGB, 70% sleeve). The average time to remission was 1.0 years. The researchers categorized participants by percentage TWL. Compared with the 0%-5% group, each 5% increase in TWL was linked with a greater likelihood of achieving remission: 5%-10%, hazard ratio 1.22 (P = .23); 10%-15%, HR 1.97 (95% confidence interval, 1.47-2.64); 15%-20%, HR 2.33 (95% CI, 1.74-3.11); 20%-25%, HR 2.81 (95% CI, 2.11-3.75); 25%-30%, HR 2.88 (95% CI, 2.16-3.83); >30%, HR, 2.92 (95% CI, 2.19-3.88). Categories above 25% TWL had remission rates similar to those of the 20%-25% group. Those in the over 20% TWL group who were taking insulin at the time of surgery had better odds of T2D remission than did those in the 0%-5% TWL group who were not taking insulin (HR, 2.18; 95% CI, 1.64-2.88).

The study is a useful addition to the literature on the topic, according to W. Timothy Garvey, MD, director of the diabetes research center at the University of Alabama at Birmingham. “This tends to quantify it a little bit more than people might have had before,” he said.

W. Timothy Garvey, MD, director of the diabetes research center at University of Alabama at Birmingham MDedge News

Dr. W. Timothy Garvey

Dr. Garvey noted that there were wide error bars in the outcomes grouped by TWL, and suggested that individual results of surgery may vary widely. “There are plenty of individuals in each of those bins that will require more weight loss for remission or less weight loss. That’s just the average of people in that weight loss category. So if a clinician is going to use this information, they need to take it with a grain of salt and realize that, just because they reach that 20% weight loss threshold, it doesn’t mean that their patient is going to go into remission. As a loose guide, as something to shoot for, I think this is valuable,” he added.

Dr. Coleman recommended that physicians not wait too long to suggest bariatric surgery, since patients are likely to have better outcomes if they are healthier going in. “Bariatric surgery is by far the most effective long-term treatment we have for severe obesity and we should be treating it as a secondary prevention strategy, not a last resort to save people’s lives. Bariatric surgery cannot regrow the cells in the pancreas that make insulin. So if we wait until patients with type 2 diabetes are insulin dependent to offer bariatric surgery, we are compromising the great effect surgery can have for them,” said Dr. Coleman.

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