Anti-Obesity Medications Reduce Weight Regain After Bariatric Surgery

Nawfal Istfan, MD, PhD

Findings of a retrospective study showed that anti-obesity medications like phentermine and topiramate can significantly reduce weight regain in patients after Roux-en-Y gastric bypass (RYGB) surgery.

“Our study provides evidence that medications can help, especially in situations where the weight gain is occurring at a rapid rate,” study author Nawfal Istfan, MD, PhD, said in a statement.

Istfan and a team of investigators aimed to evaluate the impact of anti-obesity medications on weight regain 2 years after RYGB surgery. The team used electronic health record data of adult patients who underwent bariatric surgery, specifically RYGB, at Boston Medical Center between 2004-2015. Data were extracted and included age at the time of surgery, date of enrollment in the bariatric program, date of the surgery, weight, height, and body mass index (BMI).

The investigators reviewed the data of 1516 patients who underwent surgery during the time period. The study was limited to those who underwent RYGB surgery from the 3 most common racial and ethnic groups in Boston Medical Center’s population (n=1196): African American, Hispanic, and Caucasian. If a patient became pregnant after surgery or underwent surgical revisions, they were excluded.

The primary outcome of the study was to determine the effect of anti-obesity medications on long-term weight regain. A mixed model was used to examine anti-obesity medications, race, sex, time, and presence of comorbid conditions. Covariates included age and pre-surgery BMI.

Weight loss was calculated as the difference between the pre-surgical weight and the nadir weight (lowest weight after RYGB) for each participant (n=760). The team defined weight regain as the difference between weight obtained at each subsequent office visit following the nadir date and the nadir weight.

Of the 760 participants included who achieved nadir weight and were at risk of weight regain, 46.1% were documented users of anti-obesity medications. Among the medication users, 34% were prescribed phentermine alone, 21.2% were prescribed topiramate alone, and 44% were prescribed a combination of both. There were 3 patients (.9%) prescribed lorcaserin and none were prescribed brand-name bupropion/naltrexone.

Istfan and the team found no significant differences in pre-surgery BMI and prevalence of the comorbidities included in the analysis between those who used anti-obesity medications and those who did not. The Hispanic and African American populations were more likely to use anti-obesity medication than Caucasian patients. The ORs for patients to be prescribed anti-obesity medications were 2.42 (1.74-3.36; P <.001) for African American patients and 2.85 (1.85-4.39; P <.001) for Hispanic patients compared to Caucasian patients.

Those who used the medications achieved less weight loss at nadir (P <.0001) than those who did not use such medications after bariatric surgery. Anti-obesity medications were more likely to be prescribed in patients who had sub-optimal weight loss, their effectiveness in mitigating weight regain could not be determined solely from weight trajectory.

The investigators found that anti-obesity medications decreased cumulative weight regain by about 10% relative to nadir weight. The medications also reduced the odds of rapid weight regain occurrence after the surgery.

It is necessary for future research to further explore the full potential of phentermine and topiramate and newer anti-obesity medications. What’s more, guidelines should be established to initiate and monitor the potential long-term use of such medications after bariatric surgery.

The study, “The Mitigating Effect of Phentermine and Topiramate on Weight Regain After Roux-en-y Gastric Bypass Surgery,” was published online in the journal Obesity.