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MI-BASiC: Non-diabetic patients have greater weight loss after surgery

Diabetes reduces the weight loss effect of bariatric surgery in the first three years after surgery, especially in those undergoing gastric bypass, according to the five-year outcomes from the Michigan Bariatric Surgery Cohort (MI-BASiC). However, at five-years gastric bypass has better overall weight loss compared to sleeve gastrectomy.

The MI-BASiC study included 714 patients; 564 (79%) were females with 380 patients having a gastric bypass and 334 had a sleeve gastrectomy. In the multidisciplinary program, patients undergo a preoperative evaluation and are followed postoperatively with the surgeon and dietitians at two weeks and two months. Subsequent follow-up is with the endocrinologist and dietitian at the Post-Bariatric Endocrine Clinic, where patients are asked to present at six and 12 months postoperatively, and annually thereafter to evaluate and treat long-term care issues.

They found that in patients without diabetes major weight loss outcomes in the two surgery groups lost a higher percentage of EW than patients with diabetes throughout all five years. However, this difference was diminished after three years in the total group, but still completely preserved in the gastric bypass subgroup even after five years. The researchers noted that the presence of diabetes has a greater impact on the ultimate weight loss achieved in patients undergoing gastric bypass. The patients undergoing sleeve gastrectomy also trended in the same direction early on, but the effect was lost during the later years of follow-up. To further corroborate the impact of diabetes on TWL percentage, the researchers also calculated a nadir weight for each individual and compared the nadir weight among groups with or without diabetes which yielded a p=0.0188.

Furthermore, the presence of diabetes at baseline substantially impacted the probability of achieving an outcome, with individuals without diabetes having a 1.5 times higher odds to achieve BMI under 30kg/m2 (OR 1.458, 95% CI: 1.049–2.028, p=0.025) or to achieve 50% or more EWL% (OR 1.531, 95% CI: 1.151–2.037, p=0.004) or to achieve either of these two milestones (OR 1.527, 95% CI: 1.147–2.033, p=0.004).

They then compared two major weight loss outcomes among diabetes groups, percentage of TWL and percentage of EWL between those who were on insulin and those who were not on insulin. There were 45 (30.82%) patients on insulin and 101 (69.18%) patients not on insulin in the gastric bypass group. In comparison, there were 29 (27.62%) patients on insulin and 76 (72.38%) patients not on insulin in the sleeve group. They found there was no significant difference for each procedure (p=0.58). Percentage of TWL in patients with insulin treatment and without insulin treatment was 21.25 ± 12.01% and 21.35 ± 11.43% (p=0.96), respectively. Percentage of EWL in patients with insulin treatment and without insulin treatment was 46.06 ± 26.29% and 47.06 ± 25.54% (p=0.82), respectively.

“While the mechanisms of these observations are not currently understood, our results have important practical implications for setting different expectations in patients with established diabetes versus those without and considering surgical therapies for obesity earlier in the comorbidity progression scale or intensifying treatment strategies in those with established diabetes after surgery,” the researchers concluded.

The findings were reported in the paper, ‘Impact of diabetes on weight loss outcomes after bariatric surgery: Experience from 5-year follow-up of Michigan Bariatric Surgery Cohort’, published in Clinical Endocrinology. To access this paper, please click here


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