University of Pennsylvania Engineering Publishes Nature Health AI Analysis of 400,000+ Reddit Posts from GLP-1 Users; Flags Menstrual, Temperature, and Fatigue Side Effects Underreported in Clinical Trials
A University of Pennsylvania School of Engineering and Applied Science team led by Neil K.R. Sehgal, Sharath Chandra Guntuku, Lyle Ungar, and Jena Shaw Tronieri published in Nature Health (Vol. 1, Issue 8, page 806; DOI 10.1038/s44360-026-00108-y) an AI-driven analysis of 410,198 Reddit posts from 67,008 users self-reporting use of semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound) between May 2019 and June 2025. Gastrointestinal side effects dominated as expected (nausea 36.9%, fatigue 16.7%, vomiting 16.3%, constipation 15.3%, diarrhea 12.6%), and 43.5% of users reported at least one side effect. Two categories emerged as underreported in trials and worth investigation: reproductive symptoms including menstrual cycle changes and heavy bleeding (~4%), and thermoregulation symptoms (chills, hot flashes). The authors caution that Reddit users skew younger, male, and U.S.-based and note the analysis cannot establish causation. The hypothalamus regulates hunger, hormones, reproduction, and body temperature — a plausible biological substrate. Coverage syndicated Saturday September 12, 2026 (ScienceDaily and other outlets) after the Sept 13 journal publication date.