Discordance between percentage of excess weight loss and body composition outcomes after bariatric surgery: a retrospective observational study.

BACKGROUND: Percentage of excess weight loss (%EWL) is one of the most commonly used criteria for assessing outcomes after bariatric surgery (BS). However, this measure is based on weight and does not provide information on body composition. OBJECTIVE: Our aim was to evaluate the achievement of different anthropometric objectives 12 months after BS, to analyze the concordance between %EWL and fat mass percentage (FM%) and waist-to-height ratio (WHtR) as well as to explore the differences in body composition and biochemical variables between and within groups of %EWL. METHODS: 583 participants (160 males/423 females) who underwent BS (109 sleeve gastrectomy/474 Roux-en-Y gastric bypass) were included in a retrospective observational study. %EWL, FM% and other anthropometric and biochemical variables at 12 months post-surgery were analyzed using chi-square test and one- or two-way ANOVA. RESULTS: 95% of the cohort achieved a %EWL ≥50% while 63% achieved a %EWL ≥75%. However, one-third of patients with %EWL ≥75% had a FM% still corresponding to obesity, and 65% had a WHtR ≥0.50. Patients with "High %EWL and High FM%" had higher body mass index, FM%, waist-to-hip ratio, WHtR, trunk fat percentage, visceral adiposity and relative fat mass than those with "High %EWL and Low FM%" group (P < 0.001). Patients with "High %EWL and Low WHtR" had lower levels of uric acid, blood pressure, and triglyceride-glucose index, as well as higher levels of quantitative insulin sensitivity check index than patients with "High %EWL and High WHtR" (P < 0.05). CONCLUSIONS: Body composition variability within groups remains high with a significant number of patients who, despite reaching the %EWL threshold, still exhibiting a high FM% and WHtR. Complementing the %EWL with body composition measures allows for better characterization of patients as well as identification of those with a more unfavorable metabolic state not only at diagnosis but also at follow-up.