New research shows that a weight loss plateau on GLP-1s isn’t treatment failure — it's biology
- Aug 10
- 5 min read
What can be done to help modify this predictable biological response and support long-term success.
If you've heard of GLP-1 medications, like semaglutide or tirzepatide*, you've likely heard stories of dramatic weight loss. These medications have transformed obesity treatment by helping many people lose significant amounts of weight.
But there's another part of the story that isn't discussed as often: eventually, weight loss slows — or even stops.
For many people, that moment feels discouraging. They may wonder if the medication has stopped working or if they've somehow done something wrong.
But it’s a predictable biological response to long-term weight loss, known as the weight loss plateau.
A mathematical modeling analysis led by researchers from the Medifast Metabolic Health Institute™, Scientific and Clinical Affairs Team, and members of the Medifast Scientific Advisory Board, and published in the Journal of the Academy of Nutrition and Dietetics found that plateaus are a predictable part of how the human body adapts following significant early weight loss.
What the researchers found.
Researchers used a validated mathematical model based on data from a major clinical trial (SURMOUNT-1) to examine how body weight changes during more than three years of treatment with tirzepatide.
The model followed a representative participant — a 48-year-old sedentary woman with obesity receiving weekly tirzepatide injections — and tracked changes in body weight, calorie intake, and energy expenditure over time.
The results revealed several important patterns.
Weight loss is greatest early in treatment
During the first phase of treatment, participants experience substantial weight loss.
The model predicted approximately 24% body weight loss by about 96 weeks (1.8 years) — roughly 57 pounds for the representative individual.
Though it’s not clear where the participant’s weight loss came from (healthy, quality weight loss comes from fat, especially visceral fat, while preserving muscle), that's a remarkable improvement and one of the reasons GLP-1 medications have changed the landscape of obesity care.
Then the plateau arrives.
After nearly two years, weight loss largely stabilizes, even though treatment with the medication continued.
This plateau reflects something fundamental: the body's natural response to weight loss.
Why does weight loss plateau?
To understand the plateau, it helps to think of weight loss as a balance between two factors:
Energy in: the calories you consume
Energy out: the calories your body burns
Early in treatment, GLP-1 medications significantly reduce appetite, leading people to eat about 32% fewer calories.
This creates an energy deficit, allowing weight loss to occur.
Over time, however, biology begins to adapt. As body weight decreases:
The body requires fewer calories to function
Daily energy expenditure naturally declines
Appetite gradually begins to increase again
Eventually, calorie intake and calorie expenditure become equal once again.
When that happens, the energy deficit disappears — and so does continued weight loss.
In other words, the plateau isn't a sign that treatment has failed. It's the body's attempt to establish a new balance.
How many weeks is considered a weight loss plateau?
There's no universal timeline. Some people may notice a weight loss plateau after several months of treatment, while others continue losing weight for much longer.
In this analysis, weight loss slowed and largely stabilized after approximately a year and a half (96 weeks or 1.8 years) of continuous tirzepatide treatment, illustrating that a plateau is a normal part of the body's long-term adaptation to weight loss.
Obesity is a chronic disease.
Another important finding from the study is that even after losing nearly one-quarter of their body weight, the representative participant still had a predicted BMI that remained within the obesity range.
This highlights an important reality: Weight loss — even significant weight loss — doesn't always "cure" obesity.
Like hypertension or diabetes, obesity is a chronic disease that often requires ongoing treatment and long-term management.
What happens if treatment stops?
The researchers also modeled what happened after discontinuing the medication. Within approximately four months:
Appetite rose above baseline levels
Calorie intake exceeded calorie expenditure
About 5% of body weight was regained
This reinforces findings from previous clinical studies showing that biological drivers of obesity don’t simply disappear after weight loss.
Without continued treatment — or other effective long-term strategies — the body often pushes back toward its previous weight.
Why medication alone isn't the complete solution.
GLP-1 medications are powerful tools because they help reduce hunger. But appetite is only one piece of the puzzle.
These medications don't automatically ensure:
Adequate protein intake
Preservation of lean muscle mass
Regular physical activity
Healthy sleep habits
Effective stress management
Sustainable behavior change
Those factors become increasingly important as weight loss progresses, especially once the plateau arrives.
How to get over a weight loss plateau.
Rather than viewing the plateau as the end of progress, it can be treated as the beginning of a new phase.
This is where comprehensive nutrition and lifestyle support becomes especially valuable. A structured, comprehensive approach can help people:
Preserve lean muscle while losing fat
Support metabolic health through adequate nutrition and high-quality protein
Maintain strength with regular physical activity
Build sustainable habits around eating, movement, sleep, and stress management
Reduce the risk of future weight regain
Continue improving health — even when the scale isn't changing dramatically
Success during this phase is often measured by more than weight alone. Improvements in body composition, strength, metabolic health, energy, and quality of life all matter.
The bottom line.
A weight-loss plateau on a GLP-1 medication isn't a sign that you've failed or that the medication has stopped working.
It's a predictable biological response as your body adapts to carrying less weight. And even obesity medications haven’t (at least not yet) found a workaround for overriding that piece of biology.
Understanding this can help you set realistic expectations and shift the focus from chasing continued rapid weight loss to building lifelong habits that support metabolic health.
Obesity medications can be an incredibly effective foundation for treatment. But long-term success is most likely when they're paired with comprehensive nutrition, physical activity, and other lifestyle changes that help people preserve muscle, create and maintain healthy habits, and continue improving their health for years to come.
That's why Trilivy’s metabolic health system is built around more than weight loss. It combines science-backed nutrition, coach and community support, and healthy habit creation to help people navigate every stage of their health journey — from reversing metabolic dysfunction* through healthy, quality weight loss to health optimization. Because lasting health isn't about overcoming biology — it's about working with it.
Ready to build a healthier future? Get started with Trilivy’s three-phase metabolic health system today and take the next step toward lasting metabolic health.
*Medical advice, treatment, prescriptions, and the overall practice of medicine must be provided by a licensed healthcare professional. Trilivy™ and its coaches do not engage in or provide any medical services.
**In a clinical study, 98% of lean mass was retained on the Reset 5 & 1 Plan at 16 weeks. In a clinical study, individuals on the Reset 5 & 1 Plan experienced a reduction of 14% visceral adiposity [bad fat] at 16 weeks. Arterburn LM, 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.
Reference:
Hubert PA, Coleman C, Grosicki GJ, Kiel J, Shepherd M, Lofton HF, Heymsfield SB, Thomas JG, Dhurandhar NV, Jonnalagadda SS. Mind the Plateau: A Mathematical Modeling Analysis of Long-Term GLP-1 Receptor Agonist Treatment. J Acad Nutr Diet. 2026 Aug;126(8):156366. doi: 10.1016/j.jand.2026.156366.
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