High cholesterol, older age and high BMI tied to less weight loss after gastric bypass

Last Updated: 2016-08-16

By Marilynn Larkin

NEW YORK (Reuters Health) - Preoperative hyperlipidemia, older age and a higher body mass index are associated with less weight loss after Roux-en-Y gastric bypass (RYGB), while insulin use is tied to more weight loss, researchers report.

"Bariatric surgery patients are expected to lose 30% to 40% of their body weight and up to 67% of the excess body weight, depending on the type of surgery. However, weight loss trajectories after bariatric surgery are not uniform, and some patients do not achieve or are unable to maintain expected weight losses," write Dr. Michelle Lent of the Geisinger Clinic in Danville, Pennsylvania, and colleagues in JAMA Surgery, online August 10.

To investigate, the team analyzed retrospectively collected data on 726 RYGB patients from before surgery to seven-to-12 years post-surgery. They found that the average percentage weight loss was 22.5%.

After looking at more than 200 preoperative factors, they determined that those significantly associated with greater long-term percentage weight loss were preoperative insulin use (6.8%), a history of smoking (2.8%), and use of 12 or more medications before surgery (3.1%).

Poorer long-term percentage weight loss was associated with preoperative hyperlipidemia (-2.8%), older age (-8.8%), and a higher BMI (-4.1%).

Dr. Lent told Reuters Health by email, "Bariatric surgery patients with high cholesterol, older age and higher body mass lost the least amount of weight after bariatric surgery. If clinicians know before surgery that these patients may be at risk for less weight loss, they can better tailor their treatment and help them lose as much weight as possible after surgery."

"Patients who used insulin, were taking 12 or more medications before surgery or had a history of smoking lost the most weight," she continued. "Perhaps the dietary recommendations associated with diabetes helped patients keep weight off, and perhaps patients taking high numbers of medications were motivated to lose weight to see improvements in their health. Patients must quit smoking in order to have bariatric surgery, so this history of behavior change may have helped patients also change their eating behaviors."

Dr. Lent noted that while the study used clinical data from the electronic medical record to identify patient characteristics, "including patient-reported surveys on psychosocial functioning and health behaviors in future studies would be an important next step in furthering our understanding of which patients are most successful after surgery."

Dr. Amy Neville of the University of Ottawa, author of an accompanying editorial, told Reuters Health by email that while the authors "did an excellent job exploring a number of potential explanations" for their findings, "some potential explanations - for example, that patients on many medications are more health conscious or more motivated to lose weight given their more serious medical history - unfortunately can't be tested with this kind of retrospective study."

"It is very important for us to understand predictors of weight loss after bariatric surgery as these help counsel our patients and help surgeons determine whether the balance of risks and benefits for an individual patient weighs in favor of surgery," she continued. "This study certainly contributes to this knowledge."

She added, "Unfortunately, most of these factors are not modifiable, meaning they cannot be easily changed to improve post-operative results. Hopefully, over time we will continue to identify potentially modifiable predictors of weight loss - including behavioral, psychological, and social factors - that can be acted on prior to surgery in order to improve weight loss success and sustainability long term."

Dr. Charles Billington, chief of the Minneapolis VA Health Care System's Section of Endocrinology and Metabolism, said the findings "suggest that those with greater illness may benefit more. The insulin result is surprising since other studies looking at earlier weight loss after gastric bypass have found worse results when insulin was used."

"More research will be needed on the role of diabetes and insulin on weight loss after bypass," Dr. Billington, who was not involved in the work, told Reuters Health by email.

No commercial funding or conflicts of interest were reported.

SOURCE: http://bit.ly/2bCjhXE and http://bit.ly/2bnEtfK

JAMA Surg 2016.