What Results to Expect on GLP-1 Medications for Weight Loss

Weight Loss
Written By Chris Lyons

Average weight-loss numbers from clinical trials are useful, but they hide a wide range of individual outcomes. Some patients lose more than 20% of body weight. Others lose a modest amount. A smaller group loses very little. Understanding those ranges, and why they happen, helps set realistic expectations for compounded semaglutide and tirzepatide, the two GLP-1–based medications we offer.

These medicines are not a one-size-fits-all switch. They reduce appetite, slow stomach emptying, and improve metabolic signaling. Tirzepatide also activates the GIP receptor, which is one reason it typically produces more weight loss than semaglutide in head-to-head studies. Results still depend on dose, time on therapy, sex, tolerability, and how consistently the medication is taken.

We prescribe these medications for weight management in appropriate patients who do not have diabetes. The numbers below come from the major obesity trials in that setting.

What the Major Trials Show

Semaglutide 2.4 mg (STEP 1)

 In adults with overweight or obesity and no diabetes, once-weekly semaglutide 2.4 mg produced an average weight loss of 14.9% at 68 weeks, compared with 2.4% with placebo. About 86% lost at least 5%, 69% lost at least 10%, 51% lost at least 15%, and 32% lost at least 20%. Roughly 14% lost less than 5%.

Tirzepatide (SURMOUNT-1)

 At the 15 mg dose, average weight loss in adults without diabetes was about 21% over 72 weeks. A larger share of participants reached higher weight-loss thresholds than in the semaglutide obesity trials.

Head-to-head comparison (SURMOUNT-5)

 This 72-week trial compared maximum tolerated tirzepatide (10 or 15 mg) with maximum tolerated semaglutide (1.7 or 2.4 mg) in adults with obesity and no diabetes. Average weight loss was 20.2% with tirzepatide versus 13.7% with semaglutide. That is about 22.8 kg versus 15.0 kg. Waist circumference fell 18.4 cm versus 13.0 cm. Thresholds favored tirzepatide: at least 10% weight loss in 81.6% versus 60.5%; at least 15% in 64.6% versus 40.1%; at least 20% in 48.4% versus 27.3%; at least 25% in 31.6% versus 16.1%. Gastrointestinal events were the most common side effects with both drugs and were usually mild to moderate during dose increases. Discontinuation for GI symptoms was lower with tirzepatide (2.7%) than with semaglutide (5.6%).

Real-world results are often a bit lower than trial averages because doses, follow-up, and lifestyle support vary. The pattern is still the same: most adherent patients lose a clinically meaningful amount of weight, tirzepatide usually outperforms semaglutide on average, and a minority remain poor responders.

Why Some People Respond More Than Others

1. Which medicine you are on

 Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual GLP-1 and GIP receptor agonist. Dual agonism is the main reason tirzepatide produced more weight loss in SURMOUNT-5. That does not mean semaglutide is weak. Many patients do very well on it, and some tolerate it better. If progress plateaus on semaglutide after a full titration, switching to tirzepatide is a reasonable next step for selected patients. See our post on switching from semaglutide to tirzepatide.

2. Dose and whether you can get there

 These medicines are dose-responsive. Staying at a starter dose because of nausea, skipped weeks, or delayed titration often looks like “non-response” when it is actually underdosing. A slower titration can improve tolerability and allow a higher effective dose. The goal is the highest tolerated dose that still produces progress, not the fastest climb.

3. Early trajectory

 Weight change in the first 12 to 16 weeks is one of the best practical predictors of later results. People who lose very little after reaching a therapeutic dose are less likely to become high responders later on the same regimen. Early strong responders more often finish with larger total losses. A SURMOUNT-5 analysis found that “rapid responders” (at least 15% loss by week 24) were more common with tirzepatide than semaglutide and had greater final weight loss.

4. Sex and starting body size

 Women tend to lose a larger percentage of body weight than men on both medicines. SURMOUNT-5 noted about 6 percentage points less weight loss in men than in women. People with lower starting body weight also tend to lose a higher percentage, even if the number of pounds is smaller.

5. Adherence and GI limits

 Missed doses, stopping during titration, or never reaching a maintenance dose explain a large share of disappointing results. Genetics and biology matter, but so do consistency and side-effect management.

6. Genetics play a role, but they are not the whole story

 Variants in the GLP-1 receptor gene (GLP1R) and the GIP receptor gene (GIPR) can modestly affect weight loss and nausea. Other work has identified PAM variants in a minority of people that may reduce GLP-1 signaling. These findings help explain some of the spread in outcomes. They do not currently justify routine genetic testing before treatment. Drug choice, dose, sex, and time on therapy still explain more of the day-to-day variation.

Why Some People Barely Respond

A non-response is usually defined as less than 5% weight loss after an adequate trial at a therapeutic dose. In obesity trials without diabetes, that group is often around 10% to 15% on semaglutide 2.4 mg and smaller on higher-dose tirzepatide.

Common reasons include:

  • Still on a low dose

  • Frequent missed injections

  • Stopping early because of nausea or other GI effects

  • Unrealistic time frame (full effect often takes many months)

  • Less commonly, true biologic resistance, including genetic differences in incretin pathways

“No response” is not the same as “the medicine is worthless for that person.” Some patients lose only a few percent of body weight but still improve waist size, energy, or other metabolic markers. Others need a switch from semaglutide to tirzepatide, more time at a higher tolerated dose, or tighter support around protein and resistance training.

What a Typical Timeline Looks Like

Months 1 to 3

 Appetite usually falls first. Weight loss is often modest while the dose is still being increased. GI symptoms, if they occur, are most common here.

Months 3 to 6

 This is when many patients see a clearer downward trend if they have reached a working dose. Early responders often separate from slow responders in this window.

Months 6 to 12+

 Loss typically continues, then slows as a new set point approaches. Trial averages around 14% to 21% reflect this later period, not the first few weeks. Stopping the medicine without a maintenance plan commonly leads to regain.

Quality of weight loss matters as much as the number on the scale. Combine therapy with adequate protein and resistance training to protect muscle. See protein during GLP-1 weight loss and our review of muscle changes on GLP-1 medications. For men with testosterone deficiency, optimizing hormones alongside GLP-1 therapy can further support body composition. Details are in benefits of combining GLP-1 medications with testosterone therapy.

How We Use This Information at Affinity Whole Health

We offer compounded semaglutide and tirzepatide. We start with the option that best fits a patient’s goals, medical history, and likely tolerability, then titrate based on response and side effects rather than a rigid calendar. If progress is limited after a fair trial at a therapeutic dose, we reassess adherence, dose, and whether a switch from semaglutide to tirzepatide makes sense.

We also track body composition at our in-person clinics with InBody scans, offered as a free perk, so we can see whether weight change is coming mainly from fat. Nutrition and training support are part of the plan, not an afterthought. More on that approach is in Affinity Whole Health’s ongoing metabolic support.

Expect meaningful fat loss if the medicine is tolerated and continued. Do not expect every patient to match the trial average. Super-responders and modest responders both exist, and both can still gain health if the plan is individualized.

If you are considering starting therapy, already on a GLP-1 medication, or wondering whether your current results are “enough,” we can review your trajectory and decide whether to stay the course, adjust the dose, or consider a switch.

Schedule your consultation today.

This content is for educational purposes only and does not constitute medical advice. Compounded medications are not FDA-approved. Individual results vary. Treatment decisions should be made with a qualified healthcare provider after thorough evaluation.

Key Sources

Chris Lyons
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Liraglutide vs. Semaglutide: Weight Loss, Differences, and How They Work