Recent research presented at ENDO 2026, the Endocrine Society’s annual meeting held in Chicago, Illinois, has unveiled unexpected findings surrounding the use of glucagon-like peptide-1 (GLP-1) receptor agonists in weight loss among adults with obesity. While these medications have been celebrated for their efficacy in reducing body fat, this groundbreaking study reveals a significant unintended consequence: a marked decrease in physical activity. This decline in movement raises concerns about muscle preservation and overall long-term health in individuals undergoing treatment with these drugs.
GLP-1 receptor agonists, including well-known agents such as semaglutide, liraglutide, dulaglutide, and tirzepatide, function not only to reduce adipose tissue but also have an impact on lean muscle mass. This dual effect underscores the essential role that continued physical exercise must play in treatment protocols to prevent muscle weakness and associated complications. Dr. Sajana Maharjan of HSHS St. John’s Hospital in Springfield, Illinois, who led the study, emphasized that physical activity remains a cornerstone in maintaining strength and metabolic health despite pharmacological interventions.
The study utilized a comprehensive retrospective pre–post cohort design drawing on the extensive data repository from the NIH’s All of Us Research Program. This unique dataset integrates electronic health records with objectively measured physical activity data from Fitbit wearable devices, providing a robust framework for evaluating real-world behavioral changes in physical activity tied to GLP-1 receptor agonist initiation. Among nearly two thousand adults diagnosed with obesity who began GLP-1 therapy, data adequacy criteria narrowed the analysis to 753 individuals, predominantly women, with an average age slightly over 52 years.
The investigators concentrated their analysis on two primary parameters of physical activity: daily step counts and minutes engaged in moderate-to-vigorous physical activity (MVPA). These are validated indicators of ambulatory and exercise behavior, respectively, and provide crucial insights into patients’ lifestyle adjustments following GLP-1 medication initiation. The captured data permitted a before-and-after comparison of physical activity levels with high temporal resolution afforded by wearable technology.
Quantitative results demonstrated a worrying trend. Average daily step counts fell from approximately 5,047 steps before starting treatment to 4,487 steps afterwards, indicating an over 10% reduction in ambulatory movement. Similarly, time spent in moderate-to-vigorous activity plummeted from 28 minutes per day to just 22 minutes post-treatment initiation. This diminution in physical activity contradicts the often assumed correlation between weight loss and increased mobility or exercise engagement.
Notably, the greatest decreases in physical activity were observed in male participants and individuals experiencing joint or muscle pain, suggesting that pain may be a significant barrier exacerbated or unmitigated by GLP-1 therapy. Importantly, the study accounted for potential confounders such as age, cardiovascular conditions like heart failure, and previous cerebrovascular events, none of which significantly modified the observed declines in physical activity. This points to the medication regimen and its physiological or psychological sequelae as likely drivers of decreased movement rather than underlying comorbidities.
The research team found no evidence supporting the notion that weight loss facilitated by GLP-1 receptor agonists naturally promotes increased exercise or physical engagement. This challenges prevailing assumptions and highlights a critical gap in obesity treatment paradigms, where pharmacological success may inadvertently contribute to sedentary behavior, impairing muscle maintenance and cardiometabolic fitness.
Dr. Maharjan remarked on the clinical implications of these findings, stressing that exercise must be considered a mandatory adjunct to pharmacological obesity interventions rather than an optional lifestyle component. The need for targeted, multidisciplinary interventions that actively encourage and enable patients to sustain or enhance physical activity alongside medication is paramount. Without such strategies, patients may risk losing lean muscle mass, leading to diminished functional capacity and potentially poorer health outcomes despite weight loss.
This investigation represents the first large-scale analysis that directly leverages data from wearable fitness trackers in the context of GLP-1 receptor agonist usage. The integration of digital health technologies with clinical and pharmaceutical data offers a powerful tool for uncovering real-world patient behaviors and responses. This study sets a precedent for future research exploring the intersections of pharmacotherapy, behavior, and technology in chronic disease management.
Given the widespread clinical adoption of GLP-1 receptor agonists for obesity and related metabolic disorders, these findings have immediate relevance for endocrinologists, primary care physicians, and rehabilitation specialists. They call for a reassessment of patient counseling, follow-up protocols, and interdisciplinary collaboration aimed at promoting holistic health improvements beyond weight metrics alone.
Considering the growing global obesity epidemic and the expanding role of GLP-1 medications, understanding the full spectrum of their effects—including unintended behavioral consequences—is vital for optimizing therapeutic outcomes. This study highlights an urgent need for clinical guidelines that integrate exercise prescription and perhaps novel motivational or physical therapy interventions as routine components of obesity pharmacotherapy.
Moving forward, researchers and clinicians alike must address the mechanisms underlying the reduction in physical activity associated with GLP-1 use—whether they be physiological fatigue, musculoskeletal discomfort, psychological factors, or medication side effects. Designing comprehensive care models that proactively support not only weight loss but also sustained physical activity will likely improve patient quality of life and long-term health trajectories.
In summary, the innovative use of wearable fitness data in this research elucidates a counterintuitive but clinically critical phenomenon: adults with obesity treated with GLP-1 receptor agonists may engage in less physical activity, despite losing weight. This finding underscores the necessity for integrated treatment approaches that prioritize muscle preservation and functional capacity to ensure that pharmacological advances translate into meaningful health benefits.
Subject of Research: Impact of GLP-1 Receptor Agonist Medications on Physical Activity in Adults with Obesity
Article Title: Decreased Physical Activity Among Adults with Obesity Using GLP-1 Receptor Agonists: Insights from Wearable Device Data
News Publication Date: February 17, 2026
Web References: https://www.endocrine.org/news-and-advocacy/news-room
Keywords: GLP-1 receptor agonists, obesity, physical activity, semaglutide, liraglutide, dulaglutide, tirzepatide, wearable fitness trackers, muscle mass, moderate-to-vigorous physical activity, metabolic health, exercise adherence
