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Pre-operative factors

Pre-operative factors and weight loss post-RYGB

The researchers found that preoperative insulin use, history of smoking, and use of 12 or more medications before surgery were associated with greater long-term postoperative %WL

A study of patients who underwent gastric bypass surgery found that those who used insulin prior to surgery, had a history of smoking, or took 12 or more medications maintained the greatest weight loss seven to 12 years after the surgery. The study was published by JAMA Surgery.

In the paper, ‘Evaluation of the Association Between Preoperative Clinical Factors and Long-term Weight Loss After Roux-en-Y Gastric Bypass’, by Dr Michelle R Lent, a Geisinger Obesity Institute researcher, and colleagues, evaluated the association between preoperative clinical factors and long-term weight loss after Roux-en-Y gastric bypass (RYGB).

“While bariatric surgery is the most effective long term treatment for obesity, some patients do better than others when it comes to weight loss,” said Lent. “If we can identify those patients who may be at risk for losing less weight, we can tailor their treatment to help them lose as much weight as possible.”

Michelle R Lent

Bariatric surgery patients are expected to lose 30 percent to 40 percent of their body weight and up to 67 percent 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. Preoperative clinical factors associated with long-term suboptimal outcomes are not well understood.

For this study, the researchers followed up 726 RYGB patients before surgery to seven to 12 years after surgery and determined percentage weight loss (%WL) and examined preoperative clinical factors (>200) extracted from the electronic medical record, which included medications, comorbidities, laboratory test results, demographics, and others.

Among the study participants, 83 percent were female and 97 percent were of white race, with an average preoperative BMI47.5. From the time of surgery to long-term follow-up (median, 9.3 postoperative years), the average %WL was 22.5 percent.

The researchers found that preoperative insulin use, history of smoking, and use of 12 or more medications before surgery were associated with greater long-term postoperative %WL (7 percent, 3 percent, and 3 percent, respectively). Preoperative hyperlipidemia, older age, and higher body mass index were associated with poorer long-term postoperative %WL (-3 percent, -9 percent, and -4 percent, respectively).

The authors write that possible explanations for the finding that participants taking the most medications before surgery had better weight loss outcomes are their greater interaction with health care professionals needed to manage multiple conditions or perhaps unintentional weight loss related to health conditions.

Similarly, regarding the finding that preoperative insulin users had greater %WL, "it is possible that insulin use necessitates greater interaction with the health care system, leading to better adherence and ultimately better weight loss."

The authors believe the study is the first to find that patients with diabetes and using insulin demonstrated the greatest long-term weight loss after gastric bypass surgery. Those patients lost seven percent more weight than average.

“Patients using insulin ended up being the slow, steady weight loss winners, which we did not expect,” said Lent said. “We theorise that may be because these patients are typically advised to watch their diets closely to manage their diabetes. Perhaps the dietary recommendations associated with insulin use help them lose more weight when compared with other patients.”

Smoking was a surprise since it is generally associated with worsening health outcomes. But Lent says because those patients had to quit smoking in order to have the surgery, they may have already demonstrated a history of changing their behavior to improve upon their health and are therefore also able to change their eating behaviors.

Those on the most medications also may have had the most to gain from the weight loss surgery.

“They could possibly be sicker, so they may be the most motivated to change their behavior,” said Lent. “Or those who are taking that many medications may already have more touch points within the health system, so they may be seeing doctors more frequently.”

"Overall, few preoperative clinical factors were associated with weight change in the long-term postoperative course. Future studies are needed to replicate these findings, particularly surrounding insulin use. Comprehensive investigations of potential preoperative psychosocial and behavioral factors or other modifiable preoperative or early postoperative factors that may influence weight in the long term could also help to identify patients at risk for suboptimal outcomes. These results can help to guide clinical care and improve patient-directed informed consent discussions about bariatric surgery," the researchers conclude.

In an accompanying commentary, ‘The Difficulty of Predicting Long-term Weight Loss after Gastric Bypass’, Dr Amy Neville of the Ottawa Hospital, Ottawa, Canada, noted:

"The statistical findings of this study challenge our current understanding and the current literature regarding risk factors for weight regain. As a novel (and contradictory) finding, this must be interpreted with caution until additional studies can further investigate. This study and the preoperative factors it analysed are of academic interest and may guide patient counselling and expectations, but future work must focus on behavioral predictors and other potentially modifiable risk factors if we are to best serve our patients…The results of this study appear to suggest that some of the sickest patients have the best outcomes after surgical procedures, a finding that would be new to the literature.”

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