Recent analysis explains why weight loss often stalls on GLP-1 medications

October 14, 2026 │ 3 min read

Weight loss plateau during GLP-1 treatment is a predictable biological shift, not treatment failure.

Introduction

Glucagon-like peptide-1 (GLP-1) receptor agonist medications* can lead to substantial weight loss, but weight loss often slows or stops. This analysis examined whether changes in energy intake and expenditure may explain this plateau during long-term treatment.

Research details

  • Research approachSecondary mathematical modeling analysis
  • Data sourceAverage weight-change data from 15 mg tirzepatide group in SURMOUNT-1 trial
  • Modeled profileSedentary 48-year-old female; starting weight 108 kg; BMI of 40
  • Time frame176-week treatment period + 17-week off-treatment follow-up
  • What researchers examinedChanges in body weight, BMI, energy intake, and energy expenditure over time

Main findings

  1. Weight loss peaked at week 96 (-25.9 kg or 24.0%), then plateaued for 78 weeks despite continued obesity medication treatment.
  2. Energy intake dropped by 32.1% during the first 4 weeks but later rose to match energy expenditure by week 98.
  3. Energy expenditure dropped by 9.2% by week 98, then stabilized through the rest of the treatment period.
  4. After obesity medication treatment ended, 5.7 kg body weight was regained in 17 weeks.
  5. Despite substantial weight loss, the final BMI remained in the obesity range (33.4).

What this research means

This mathematical modeling simulation shows that despite significant weight loss on GLP-1 medications, the weight loss slows and eventually plateaus. This analysis offers a physiologic explanation. Early in treatment, decreased energy intake creates the energy deficit needed for weight loss. As body weight drops, the body adapts: energy expenditure decreases while energy intake rises. Once the two become similar, weight stabilizes. Substantial weight loss also does not always resolve obesity. Because this was a mathematical model simulation using average trial data, individual timelines and responses will vary.

Conclusion

Stalled weight loss during GLP-1 treatment should not automatically be viewed as treatment failure. Preparing for a plateau by including nutrition, physical activity, and behavioral support throughout treatment may help people navigate through this stage and maintain progress, especially if medication is discontinued.

Citation

Hubert, P. A., Coleman, C., Grosicki, G. J., Kiel, J., Shepherd, M., Lofton, H. F., Heymsfield, S. B., Thomas, J. G., Dhurandhar, N. V., & Jonnalagadda, S. S. (2026). Mind the plateau: A mathematical modeling analysis of long-term GLP-1 receptor agonist treatment. Journal of the Academy of Nutrition and Dietetics, 126(8), 156366. https://doi.org/10.1016/j.jand.2026.156366

Madelyn Shepherd

Written by

Madelyn Shepherd, MPH, CHES®
Senior Health & Nutrition Educator at Medifast, Inc.

*In a clinical study, individuals on the Trilivy Reset Plans experienced a reduction of 14% visceral fat and 97 to 98% of lean mass was retained at 16 weeks. Arterburn LM, Coleman CD, Kiel J, et al. Randomized controlled trial assessing two commercial weight loss programs in adults with overweight or obesity. Obes Sci Pract. Feb 2019;5(1):3-14. doi:10.1002/osp4.312.

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