Replication and extension of dietary adherence as a predictor of suboptimal weight-loss outcomes in postbariatric patients

Background: Sarwer et al. found that poor dietary adherence at 6 months postoperatively predicted lower weight loss. Objectives: To replicate and extend these findings. Setting: University bariatric clinic. Methods: Fifty-four adults (72% female; age 51.1 +/- 11.3 yr; mean body mass index [BMI] = 43.8 +/- 7.4 kg/m(2); 53.7% = Roux-en-Y gastric bypass, 42.6%=laparoscopic sleeve gastrectomy, and 3.7%=gastric banding) were identified as low or high dietary adherers following the method of Sarwer et al. Patients self-reported dietary adherence with a 9-point Likert scale. Splitting the group at the median, low adherers scored <7 and high dietary adherers >= 7. BMI, percentage excess weight loss (%EWL), and percentage total weight loss (%TWL) were prospectively assessed at 12, 24, and 36 months. Two-tailed independent t tests and Cohen's d effect sizes were used to compare between-group outcomes. Results: BMI did not differ between low (n = 24) and high (n = 30) dietary adherers at 6 months after surgery. At 12 months, the BMI of low (n=17) adheres was significantly higher (34.1 +/- 4.61 versus 30.3 +/- 3.90 kg/m(2), P= .006, d=0.90) than that of high (n =25) adherers, with significantly less %EWL (49.0 +/- 24% versus 70.7 +/- 21.5%; P= .004; d= 0.95) and %TWL (20.7 +/- 11.5% versus 28.9 +/- 10.5, P = .02, d = 0.74). At 24 months, BMI remained significantly higher for low (n=12) versus high (n=10) adherers (33.7 +/- 4.77 versus 29.7 +/- 3.82 kg/m(2), P=.045, d=0.92), but %EWL and %TWL were not significantly different, despite large effect sizes. At 36 months, moderate effects supported continued higher BMIs and lower %EWL and %TWL for low (n=5) versus high (n=8) adherers. Attrition from follow-up was 22.2% (12 mo), 59.3% (24 mo), and 75.9% (36 mo). Post hoc analyses revealed no impact of baseline characteristics on low follow-up rates except younger age (at 1 yr). Conclusions: Findings that 6-month postoperative dietary adherence predicts 12-month BMI, %EWL, and %TWL were replicated. Medium to large effects suggest findings extend to 24 and 36 months, with low follow-up rates likely affecting statistical significance. (C) 2018 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.