GLP-1 before and after: what the numbers actually show at 40+

Search "GLP-1 before and after" and you get two extremes. There are dramatic photos with no context, and forum posts saying the drug did nothing. The trial data sits in between. It is duller, more specific and more useful for judging your own progress.

How much weight do people lose on a GLP-1?

The clearest numbers come from the large randomized trials. In STEP 1, adults without diabetes on semaglutide 2.4 mg, the Wegovy dose, lost about 15% of their weight over 68 weeks. People on placebo lost about 2%.

In SURMOUNT-1, tirzepatide, sold as Zepbound, was tested at three doses for 72 weeks. People lost about 15% on 5 mg, about 20% on 10 mg and about 21% on 15 mg. People on placebo lost about 3%.

An average hides a wide spread. In STEP 5, about 3 in 4 people on semaglutide had lost at least 5% of their weight after two years, against about 1 in 3 on placebo. So about 1 in 4 did not reach 5%. If your number is below the headline, you may simply be in a different part of that range.

Which GLP-1 gets better results: semaglutide or tirzepatide?

There is now a head-to-head trial. In SURMOUNT-5, adults with obesity and no diabetes took one drug or the other for 72 weeks. Tirzepatide averaged about 20% weight loss, against about 14% for semaglutide. If a bigger number is what matters most to you, tirzepatide has the stronger case.

Semaglutide has since added a higher dose. In STEP UP, people on the 7.2 mg dose, sold as Wegovy HD since 2026, lost about 19%. People on 2.4 mg lost about 16%, and on placebo about 4%. That narrows the gap without closing it. It comes from a different trial, and no study has tested 7.2 mg against tirzepatide.

A bigger average is not the only thing to weigh. Price, insurance coverage and how you handle side effects matter too, and they differ by drug and dose.

What does a realistic before-and-after timeline look like?

The scale does not move in a straight line. Both drugs start at a low dose and step up, each step after at least four weeks. The GLP-1 dosage chart shows the steps for each drug. The timeline follows the dose, not a fixed calendar.

• First weeks: you are on a starting dose meant to ease side effects. Many people notice appetite changes before the scale moves much.
• Months 2 to 5: the dose keeps climbing. In STEP 1, semaglutide reached its full 2.4 mg dose after 16 weeks. In SURMOUNT-1, tirzepatide took up to 20 weeks to reach the top dose.
• 68 to 72 weeks: this is where the big trials measured their headline results, about 15% for semaglutide and about 15% to 21% for tirzepatide.
• Two years: in STEP 5, people on semaglutide had still lost about 15% at 104 weeks, against about 3% on placebo. The loss held rather than kept growing.

Does a GLP-1 work differently if you're not diabetic?

Yes, and the difference works in your favor. STEP 1 enrolled adults without diabetes, who lost about 15%. STEP 2 gave the same dose for the same 68 weeks to adults with type 2 diabetes. They lost about 10%, against about 3% on placebo.

Why people with diabetes lose less is not fully settled. What matters for you: if you don't have diabetes, the trial group you most resemble lost more.

How do GLP-1 drugs work for weight loss?

GLP-1 is a hormone your gut makes after you eat. These drugs copy it and stay active much longer. They act on appetite centers in the brain, slow how fast the stomach empties, and help the pancreas release insulin when blood sugar is high.

Tirzepatide also acts on a second gut hormone, called GIP. That may help explain its larger average results, though researchers are still sorting out how much. Either way, less hunger and earlier fullness do most of the visible work. For more, see what is a GLP-1 and how does it work.

Why might your results look different in perimenopause?

This has been studied directly. A 2025 analysis in the journal Obesity sorted women in the tirzepatide trials by menopause stage. In SURMOUNT-1, on 15 mg or the highest dose they could tolerate, premenopausal women lost about 26%, against about 2% on placebo. Women in perimenopause and after menopause each lost about 23%, against about 3%.

The authors concluded tirzepatide worked whatever the stage. The few points between groups were not the question the study tested. So the honest read is reassuring: the drug still works well in a body going through the transition.

Hormone therapy is a separate decision. The GLP-1 and menopause guide covers how hormone therapy and a GLP-1 compare and which problem each one solves.

What decides your own results?

Trial averages show the shape of the curve. They don't predict your number. These factors matter most:

• The dose you reach and tolerate. In SURMOUNT-1, people on 5 mg lost about 15% and people on 15 mg about 21%.
• How steadily you take it. Missed or late weekly doses interrupt the steady drug level these medicines rely on.
• Where you start. Starting weight and metabolic health shape how much loss is realistic. That is biology, not a personal failing.
• How long you stay on it. The headline numbers took more than a year to reach.
• Individual variation. Some of the spread between people is still not explained.

Is hitting a plateau normal?

Yes. In STEP 5, average weight loss at two years was about the same as the trials found at 68 weeks. The study calls it sustained. That pattern is the body settling at a new, lower weight once the dose is stable, not the drug failing.

A long plateau on a dose you tolerate well is worth raising with your prescriber, who can check whether a dose change makes sense. Weight climbing back up on an unchanged dose is a different pattern and deserves a closer look.

Does the weight come back if you stop?

For most people, much of it does. In the STEP 1 extension, people stopped semaglutide after 68 weeks, having lost about 17%. A year later they had regained about two-thirds of it, for a net loss of about 6%. Most heart and metabolic gains also faded.

In SURMOUNT-4, people who switched from tirzepatide to placebo after 36 weeks regained about 14% of their weight over the next year. Those who stayed on it lost about 5.5% more. The trials point the same way: these drugs treat an ongoing condition, like blood pressure medicine does.

Does the scale tell the whole story?

Not entirely. Part of the weight lost on these drugs is lean tissue, including muscle, not only fat. In the semaglutide trials, about 4 in every 10 pounds lost were lean mass. In SURMOUNT-1, about a quarter was. That matters more after 40, when falling estrogen already works against muscle.

Our guide to GLP-1 muscle loss in perimenopause covers the body-composition data and how to protect your strength.

What does it cost, and where do you start?

Cost varies by drug, dose, insurance and provider, so one number would mislead. Brand-name drugs have the highest list prices, but the makers now sell them for less to people paying cash. Compounded versions can cost less but are not FDA-approved. Insurance coverage depends on whether your plan covers obesity drugs at all.