Keeping weight off after GLP-1s: muscle, plateaus and what happens when you stop

I trained in Physical Medicine & Rehabilitation, a specialty that measures success by what people can do: climb stairs, carry groceries, get up off the floor, stay independent. That lens changes how I think about weight loss. A lower number on the scale is useful when it comes with preserved strength and a plan for the years after. It is much less useful when it costs muscle and ends in regain.

I also have a personal stake in this. Over one year I lost roughly 100 pounds, during a weight-loss journey that included GLP-1 therapy. That is my own experience, not a result anyone should expect — but it taught me that the hard questions arrive after the early months, not during them.

Why some of the weight lost is lean mass

Any substantial weight loss — from diet, surgery or medication — removes some lean tissue along with fat. “Lean mass” on a body-composition scan includes muscle, but also water, organs and other non-fat tissue, so it is not a pure measure of muscle lost.

The pivotal trials measured this with DXA scans in subsets of participants. In the STEP 1 semaglutide trial, lean mass accounted for roughly two-fifths of the weight lost in the scanned group.¹ In the SURMOUNT-1 tirzepatide substudy, about three-quarters of the weight lost was fat and about a quarter was lean mass.² These were different trials with different methods, so they should not be read as a head-to-head comparison. Both substudies were of the FDA-approved products, and their findings cannot be assumed to apply to compounded versions. The shared lesson is simple: lean mass needs protecting, and the tools for that are mostly not pharmaceutical.

It matters more for some people than others. If you are older, already have low muscle mass, have joint pain that limits activity, or are losing weight quickly, preserving strength deserves more attention, not less.

Protein when appetite is low

Reduced appetite is the point of these medicines, but it can quietly reduce protein intake along with everything else. A 2025 joint advisory from four obesity and nutrition societies lists adequate protein intake and strength training to preserve lean mass among the core nutritional priorities for people taking GLP-1 medicines, alongside avoiding micronutrient deficiencies.³

In practice that means putting protein first at each meal, spreading it across the day rather than saving it for dinner, and using simple, well-tolerated sources when a full meal is not appealing. The right target depends on your body size, activity, kidney function and diet, so it is set individually rather than copied from the internet. If you have kidney disease, protein targets need particular care.

Resistance training, adapted to your joints

Resistance training is the most effective signal you can send a muscle that it is still needed. The U.S. Physical Activity Guidelines recommend muscle-strengthening activities involving all major muscle groups on two or more days a week, alongside 150 to 300 minutes of moderate aerobic activity.⁴ Many people starting a weight-loss program are nowhere near that, and that is fine; the goal is a starting point you can keep.

This is where a rehabilitation background helps. Knee arthritis, a painful shoulder or low-back pain are reasons to choose different exercises, not reasons to skip strength work. Chair-based and band-based programs, supported machines and water-based exercise all count. When pain is the barrier, it is worth evaluating directly — sometimes through PrimeCell’s pain care, sometimes with a physical therapist.

Why plateaus happen

In both STEP 1 and SURMOUNT-1, average weight loss was fastest in the early months, then slowed and leveled off in the final months of treatment.^5,6 That curve is not the medicine failing. As weight falls, the body needs less energy and appetite-regulating systems push back; at some point intake and expenditure meet at a new, lower set point.

A plateau is a reason to review the whole plan rather than simply raise the dose. At that visit we look at what you are actually eating (including whether protein has slipped), sleep, alcohol, activity and strength, other medicines, side effects and whether the current weight is already a healthy place to hold. Sometimes a dose change makes sense. Sometimes the right move is to shift the goal from losing to maintaining.

What happens when the medication stops

Three trials looked directly at this question, and their answer is consistent.

• STEP 1 extension (semaglutide). After 68 weeks of treatment, participants stopped both the medicine and the trial’s lifestyle program. One year later they had regained about two-thirds of the weight they had lost, and improvements in blood pressure, blood sugar and other cardiometabolic measures moved back toward baseline. On average, they still weighed less than when they started.⁷
• STEP 4 (semaglutide). After a 20-week lead-in in which participants lost an average of about 10.6% of body weight, those randomized to continue lost a further 7.9% over the next 48 weeks, while those switched to placebo regained 6.9%.⁸
• SURMOUNT-4 (tirzepatide). After a 36-week lead-in with average weight loss of about 20.9%, those who continued lost a further 5.5% over the following year, while those switched to placebo regained 14.0%.⁹

These are trial averages from studies of the FDA-approved products, which cannot be assumed to apply to compounded versions,¹⁰ and some individuals held their weight better than others. But the pattern is clear enough to plan around: for many people, obesity behaves like a chronic condition, and the effect of these medicines depends on continuing them.

How a maintenance plan is built

PrimeCell’s GLP-1 program uses compounded GLP-1 medications, prescribed only after a physician evaluation. Compounded drugs are not FDA-approved, and the FDA does not review them for safety, effectiveness or quality. They are not the same as, and should not be assumed equivalent to, Wegovy or Zepbound.

In the PrimeCell GLP-1 program, maintenance is discussed at the first visit and planned in earnest as progress slows. The options are usually some combination of these:

1. Continue at the dose that got you here, with strength and protein habits established. This is the approach with the strongest trial evidence, although that evidence comes from the FDA-approved products.
2. Adjust — for example, a lower dose. This is a common clinical approach, but the evidence for dose-reduction strategies is more limited than for continuation, and we say so.
3. Stop, with structure. Sometimes cost, side effects, pregnancy plans or personal preference make stopping the right choice. Then the plan includes regular weigh-ins, a defined threshold for returning to discuss options, and the habits that make the difference: protein, strength training, sleep and a realistic eating pattern.

Whatever the choice, it is made with you, written down, and revisited. It should never be a surprise. If candidacy is still the open question for you, start with who is a candidate for GLP-1 weight loss; if side effects are the worry, read GLP-1 side effects and monitoring.