How much weight do people with type 2 diabetes lose on a GLP-1? What STEP 2 and SURMOUNT-2 found

The short version

In STEP 2, adults with type 2 diabetes on weekly semaglutide 2.4 mg lost 9.6% of their body weight on average over 68 weeks, vs 3.4% on placebo.¹
In SURMOUNT-2, adults with type 2 diabetes on weekly tirzepatide lost 12.8% (10 mg) or 14.7% (15 mg) over 72 weeks, vs 3.2% on placebo.²
Both results are smaller than in the matching trials of people without diabetes. They are still large compared with placebo.^3,4

Why these trials matter

The trials behind the best-known weight-loss numbers, STEP 1 for semaglutide and SURMOUNT-1 for tirzepatide, did not include people with type 2 diabetes. Yet many people who use these medicines for weight also have diabetes. STEP 2 and SURMOUNT-2 were designed to answer the question for them.

Both trials enrolled adults with a BMI of at least 27 and an HbA1c (a three-month average of blood sugar) between 7% and 10%. Everyone also got lifestyle support, so the placebo group shows what that support did on its own.^1,2

Illustration of two curving lines on a grid.

STEP 2: semaglutide 2.4 mg

STEP 2 enrolled 1,210 adults at 149 clinics in 12 countries. All had been diagnosed with type 2 diabetes at least 180 days before. They were split evenly into three groups for 68 weeks: semaglutide 2.4 mg, semaglutide 1.0 mg (the dose already used for diabetes), or placebo, all once a week.¹

−9.6%average weight change on semaglutide 2.4 mg at week 68

−3.4%average weight change on placebo

68.8%on 2.4 mg lost at least 5% of their weight, vs 28.5% on placebo

The gap between semaglutide 2.4 mg and placebo was 6.2 percentage points. The trial was built to compare 2.4 mg with placebo, and that is the main result reported.

SURMOUNT-2: tirzepatide 10 mg and 15 mg

SURMOUNT-2 enrolled 938 adults in seven countries. Their average age was 54, about half were women, the average starting weight was 100.7 kg, the average BMI was 36.1 and the average HbA1c was 8.0%. They were split evenly into tirzepatide 10 mg, tirzepatide 15 mg or placebo, once a week for 72 weeks.²

Tirzepatide 15 mg−14.7%

Tirzepatide 10 mg−12.8%

Placebo−3.2%

Compared with placebo, the difference was 9.6 percentage points with 10 mg and 11.6 with 15 mg. Between 79% and 83% of people on tirzepatide lost at least 5% of their weight, vs 32% on placebo.²

Compared with trials in people without diabetes

The same medicines led to more weight loss in people without diabetes. The table puts the numbers next to each other.

Average percent change in body weight on the medicine. Sources: STEP 1, STEP 2, SURMOUNT-1, SURMOUNT-2.^3,1,4,2
Medicine	Without diabetes	With type 2 diabetes
Semaglutide 2.4 mg	−14.9% (STEP 1, 68 weeks)	−9.6% (STEP 2, 68 weeks)
Tirzepatide 10 mg	−19.5% (SURMOUNT-1, 72 weeks)	−12.8% (SURMOUNT-2, 72 weeks)
Tirzepatide 15 mg	−20.9% (SURMOUNT-1, 72 weeks)	−14.7% (SURMOUNT-2, 72 weeks)

The trials were not built to explain the gap, so this article does not try to. What the numbers do suggest is practical: if you have type 2 diabetes, the average results from STEP 1 or SURMOUNT-1 may set expectations a little too high.

These are separate trials, so the comparison is a rough guide. STEP 2 and SURMOUNT-2 also did not test semaglutide and tirzepatide against each other. For a head-to-head trial, see semaglutide vs tirzepatide.

Side effects

In both trials, the most common side effects were in the stomach and gut, such as nausea, diarrhea and vomiting, and most were mild to moderate.^1,2

Share of participants reporting at least one event. Source: STEP 2.¹
STEP 2	Semaglutide 2.4 mg	Semaglutide 1.0 mg	Placebo
Any gastrointestinal side effect	63.5%	57.5%	34.3%
Any side effect	87.6%	81.8%	76.9%

In SURMOUNT-2, fewer than 5% of people stopped tirzepatide because of side effects. Serious side effects were reported by 7% of all participants across the three groups.² For more on what tends to help, see GLP-1 nausea and stomach side effects.

Reading these results

Who was studied. Adults with type 2 diabetes, a BMI of 27 or more and an HbA1c of 7–10%. The results may not apply to people with type 1 diabetes or with very high or very well-controlled blood sugar.
Other diabetes medicines. STEP 2 grouped participants by the diabetes medicines they already took. If you take other diabetes medicines, ask your care team how adding a GLP-1 may affect them.
Averages hide a wide range. In STEP 2, about 3 in 10 people on semaglutide 2.4 mg did not reach 5% weight loss, while others lost far more than the average.
Long-term use. These were 68- and 72-week trials. For what happens over two to three years, see long-term GLP-1 results.

Which medicine, which dose and whether it fits alongside your current treatment are decisions to make with your prescriber.

Sources

Davies M, Færch L, Jeppesen OK, et al. Semaglutide 2·4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2): a randomised, double-blind, double-dummy, placebo-controlled, phase 3 trial. Lancet. 2021;397:971-984. PubMed · doi:10.1016/S0140-6736(21)00213-0
Garvey WT, Frias JP, Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2): a double-blind, randomised, multicentre, placebo-controlled, phase 3 trial. Lancet. 2023;402:613-626. PubMed · doi:10.1016/S0140-6736(23)01200-X
Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384:989-1002. PubMed
Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387:205-216. PubMed

This article summarises published research for general information. It is not medical advice and does not replace advice from your own care team. Never change a medication or dose without talking to your prescriber.