November 1, 2026 | GLP-1 medications

Semaglutide vs. tirzepatide: why does one person lose more weight than another?

Two people can start weight-loss treatment around the same time, take medication consistently, and still see very different results. The research helps explain why, but the story is more complicated than simply comparing two numbers.

Imagine two people who start weight-loss treatment around the same time.

Both are taking medication consistently. Both are trying to make healthier food choices. Both are hoping to see meaningful changes.

A few months later, one is excited about the number on the scale. The other is frustrated because the results are not coming as quickly as expected.

They start comparing notes. Same type of medication, perhaps even the same brand. So why are their experiences so different?

It is one of the biggest questions surrounding today's weight-loss medications.

And it leads to another: if tirzepatide produces greater average weight loss than semaglutide, does that automatically make it the better choice?

First, why are these medications different?

Semaglutide and tirzepatide are often discussed together because both influence hormones involved in appetite, digestion, and blood sugar regulation.

But they do not work in exactly the same way.

Semaglutide: one hormone pathway

Semaglutide activates the GLP-1 receptor.

GLP-1 is a hormone naturally released by the gut after eating. It helps regulate appetite, supports blood sugar control, and slows the movement of food through the stomach.

For someone taking semaglutide, this can translate into some noticeable everyday changes:

• Feeling full after eating a smaller portion.
• Not thinking about food as frequently.
• Finding it easier to leave food on the plate.
• Feeling less hungry between meals.

Some people describe the reduction in persistent thoughts about food as a decrease in "food noise."

Semaglutide is the active ingredient in medications such as Wegovy and Ozempic. Although they contain the same active ingredient, their approved uses and dosing instructions are not interchangeable.

Tirzepatide: two hormone pathways

Tirzepatide activates two receptors: GIP and GLP-1.

GIP is another hormone involved in the body's response to food and blood sugar. By targeting both pathways, tirzepatide produces a different hormonal response from semaglutide.

Its effects can include reduced appetite, increased feelings of fullness, and improved blood sugar regulation.

Tirzepatide is marketed as Zepbound for weight management and certain other approved uses, and as Mounjaro for type 2 diabetes in the United States.

The basic difference is straightforward: semaglutide targets one hormone pathway. Tirzepatide targets two.

What happens when researchers compare them directly?

For a long time, people compared weight-loss results from separate clinical trials. The problem is that different trials can involve different participants, doses, treatment periods, and study conditions.

A direct comparison is much more useful.

In 2025, researchers published the results of SURMOUNT-5 in The New England Journal of Medicine. The study included 751 adults with obesity who did not have type 2 diabetes. Participants were randomly assigned to receive either tirzepatide or semaglutide for 72 weeks.

Researchers compared the maximum tolerated doses:

• Tirzepatide: 10 mg or 15 mg weekly.
• Semaglutide: 1.7 mg or 2.4 mg weekly.

Both groups also received guidance on a reduced-calorie diet and increased physical activity.

The difference is significant.

Imagine someone starting at 250 lbs:

• A 20.2% reduction would equal about 50.5 lbs.
• A 13.7% reduction would equal about 34.3 lbs.

That's an average difference of approximately 16.2 lbs.

But there is another result worth noticing. Almost 27% of participants taking semaglutide also lost at least 20% of their starting weight.

In other words, even though tirzepatide produced better average results, some people taking semaglutide achieved substantial weight loss too.

This is an important distinction: a medication can have a higher average result without producing a better result in every individual.

The trial was open-label, meaning participants and researchers knew which medication was being used. It was funded by Eli Lilly, the manufacturer of tirzepatide. These details are worth knowing when interpreting the findings.

Why did tirzepatide produce greater average weight loss?

The obvious question is whether targeting two hormone pathways instead of one explains the difference.

It is a plausible part of the explanation. Tirzepatide's dual GIP and GLP-1 activity produces a different biological response, and the clinical results have been impressive.

However, researchers are still investigating exactly how the two pathways contribute to its greater average weight-loss effect.

The direct comparison establishes that tirzepatide produced greater average weight loss in the study. It does not establish precisely how much of that difference comes from each biological mechanism.

There is also evidence from a separate study involving people with type 2 diabetes. In the 2021 SURPASS-2 trial, researchers compared tirzepatide with semaglutide in 1,879 adults with type 2 diabetes who were taking metformin.

After 40 weeks, average weight reductions were 16.8 lbs with tirzepatide 5 mg, 20.5 lbs with tirzepatide 10 mg, 24.7 lbs with tirzepatide 15 mg, and 12.6 lbs with semaglutide 1 mg.

But there is an important difference between these studies: SURPASS-2 involved people with type 2 diabetes and compared tirzepatide with semaglutide 1 mg. SURMOUNT-5 involved people without type 2 diabetes and compared higher obesity-treatment doses.

The results should not be directly combined or treated as identical comparisons. Still, both studies point in the same general direction: tirzepatide produced greater average weight loss in the populations and at the doses studied.

Why doesn't everyone lose the same amount?

If a medication works by reducing appetite, shouldn't everyone experience a similar effect?

Not necessarily.

Two people can take the same medication and have very different experiences. One might notice a dramatic reduction in hunger. Another might feel only a modest difference. One might lose weight steadily. Another might lose weight initially, plateau, and then see progress again.

1. The starting point matters

Two people weighing the same amount do not necessarily have the same health profile. Age, body composition, diabetes status, other medical conditions, and medications can all be relevant.

For example, people with type 2 diabetes may experience different average weight-loss results from people without diabetes. This is one reason the results from SURMOUNT-5 should not automatically be applied to every person taking these medications.

2. Not everyone reaches the same dose

These medications are generally introduced gradually. The dose is increased over time to help the body adjust and improve tolerability.

Some people reach the higher maintenance doses used in clinical trials. Others may remain at lower doses because of side effects or individual treatment considerations.

So when someone says, "I'm taking the same medication, but I'm not losing as much," it is worth asking whether they are actually taking the same dose and have been on treatment for a similar length of time.

The medication name alone does not tell the whole story.

3. Appetite suppression isn't identical for everyone

One person may say they no longer think about food constantly. Another may still experience hunger but find that smaller portions are satisfying.

Someone else may notice that their appetite is reduced at first but becomes more noticeable again over time.

These experiences do not necessarily mean one person's medication is working and another's is not. Appetite, fullness, and food-related thoughts are complex experiences. They do not always change in the same way or at the same pace.

4. Other health and lifestyle factors matter

Sleep, physical activity, eating patterns, other medications, and underlying health conditions can influence weight.

These factors do not explain every difference, and they are not a reason to blame someone for slower progress. They are simply part of a much bigger picture.

Researchers are also studying genetic and biological differences that may help explain why some people respond more strongly to certain medications. We do not yet have a reliable test that can predict exactly how much weight an individual will lose or which medication will work best for them.

What happens when weight loss slows down?

A common experience is losing weight steadily for several months and then suddenly seeing the scale barely move. It is frustrating, particularly when someone feels they are doing everything the same way.

But weight loss is not always a straight downward line.

As body weight decreases, the body generally needs less energy than it did at a higher weight. Appetite and energy-regulation mechanisms can also change during weight loss.

A slower rate of progress does not automatically mean the medication has stopped working.

It is also important to distinguish between a temporary plateau and a longer-term lack of meaningful response. Those are different situations and deserve individual assessment with a healthcare professional.

What about side effects? Does more nausea mean more weight loss?

Both medications can cause gastrointestinal side effects. Commonly reported symptoms include nausea, diarrhea, constipation, vomiting, abdominal discomfort, indigestion, and acid reflux.

These symptoms are often more noticeable when treatment begins or the dose is increased. In SURMOUNT-5, gastrointestinal symptoms were the most common adverse events with both medications, and most were mild to moderate.

But there is a misconception worth addressing: experiencing more nausea does not mean a medication is working better.

Someone can lose substantial weight without experiencing much nausea. Another person may experience unpleasant gastrointestinal symptoms without achieving the weight loss they expected. Side effects are not a reliable way to measure effectiveness.

Both medications also have important safety warnings, including risks involving pancreatitis, gallbladder problems, and kidney injury associated with dehydration.

They carry a boxed warning about thyroid C-cell tumors observed in rodents. Whether this risk applies to humans is unknown. They should not be used by people with a personal or family history of medullary thyroid carcinoma or by people with Multiple Endocrine Neoplasia syndrome type 2 (MEN2).

There are also differences worth knowing about:

• Semaglutide used for weight reduction should be discontinued at least two months before a planned pregnancy.
• Tirzepatide may reduce the effectiveness of oral hormonal contraceptives. Its prescribing information advises using a non-oral contraceptive method or adding a barrier method for four weeks after starting treatment and four weeks after each dose increase.

These are examples of why medication decisions need to consider more than weight-loss results. The full prescribing information should always be reviewed with a healthcare professional.

If one produces more weight loss, why would someone consider the other?

Because weight loss is not the only health outcome that matters.

Both medications have important benefits, but their approved uses are not identical.

For example:

• Wegovy has an FDA-approved indication to reduce certain cardiovascular risks in eligible adults with established cardiovascular disease and overweight or obesity.
• Wegovy also has an accelerated FDA approval for certain adults with noncirrhotic MASH and moderate-to-advanced liver fibrosis.
• Zepbound has an FDA-approved indication for moderate-to-severe obstructive sleep apnea in adults with obesity.

These are specific indications for particular patient groups, not benefits that automatically apply to everyone taking the medication.

A healthcare professional may also consider diabetes status, other health conditions, previous treatment experiences, side-effect tolerance, cost, and insurance coverage.

The medication with the highest average weight-loss result is not automatically the best choice for every person.

What should someone take away from all this?

The research gives us a clear finding: in a direct 72-week comparison involving adults with obesity without type 2 diabetes, tirzepatide produced greater average weight loss than semaglutide.

That is an important difference. But the study also showed that substantial weight loss was possible with both medications.

And outside clinical trials, people bring different health histories, treatment experiences, doses, and biological responses.

So if someone loses 20% of their starting weight while another person loses 8%, the difference does not automatically mean one person succeeded and the other failed.

The numbers tell us what happened across groups of people. They cannot tell us exactly what will happen to any one individual.

Perhaps that is the most important thing to remember when reading about these medications: your progress is not a competition with somebody else's results.

Sources and further reading

1. Aronne LJ et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. Read the study.
2. Frias JP et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. Read the study.
3. FDA prescribing information: Wegovy (semaglutide).
4. FDA prescribing information: Zepbound (tirzepatide).