SAT-LB019 Improvement of Visceral Fat and Body Composition Endpoints in Participants on Prescription Thyroid Replacement with a Doctor-Supervised Weight Loss Program

Background: The obesity epidemic in the US is highlighted by CDC estimates that ~40% of the US population is obese (Flegal). Given the complex role of the thyroid in metabolism, it’s relationship to weight regulation, and conflicting evidence of weight gain or loss as a result of prescription thyroid replacement (THR), it is important to understand how THR affects weight loss efforts beyond the standard measures of body weight % and BMI. Methods: We examined differences in body composition improvement in individuals taking and not taking THR over 60 days of a doctor supervised weight loss and metabolic health program (The 20Lighter Program, T20LP). Results: Of 2200 participants completing the T20LP, ~10% reported taking prescription THR. In both groups (THR, non-THR) baseline age, comorbidities, and prescription medications were typical of metabolic syndrome. From initial baseline to 60 days (completion of T20LP), participants from both groups showed statistically significant and clinically meaningful reductions in body weight (12.8±0.30%, 14.0±0.22%), BMI (12.86±0.31%, 13.92±0.24%), body fat % (14.61±0.34%, 15.62±0.39%), visceral fat (24.6±0.64%, 26.3±0.39%), metabolic age (18.47±0.32%, 19.76±0.44%), and increases in body water % (7.86±0.129%, 8.09±0.127%). While small numerical divergence in mean change was found favoring the non-THR group, none held statistical significance. Discussion: The scientific literature examining the relationship between THR and weight loss includes studies and reviews with small data sets and limited endpoints. To our knowledge, our study is the first large scale analysis comparing body composition outcomes beyond weight and BMI specifically in participants who take THR and those who do not. Our endpoints include body fat %, visceral fat (a well-characterized direct marker of CV and metabolic disease risk (DesPres, Goran)), and body water % (a gauge of tissue hydration). Our data show both groups do equally well with respect to % body weight lost, BMI reduction, body fat and visceral fat reduction, and improvement in tissue hydration, and we found no disadvantage in any physiologic or metabolic outcome in participants on THR. Conclusion: Despite contradictory historical evidence, weight loss participants requiring prescription THR are capable of achieving clinically meaningful and statistically significant body composition and metabolic improvements. References: Flegal KM, et al. Trends in Obesity Among Adults in the United States, 2005 to 2014. JAMA 2016;315(21):2284-2291. DesPres JP. Body fat distribution and risk of cardiovascular disease: an update. Circulation 2012; 126:1301-1313. Goran MI, Gower BA. Relation between visceral fat and disease risk in children and adolescents. Am J ClinNutr 1999; 70(1):149S-156S. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.