GLP-1 Weight Loss With Type 2 Diabetes: Why Outcomes Can Differ

If you have type 2 diabetes and your weight loss on a GLP-1 looks smaller than the numbers in the headlines, you're not imagining the gap. In the big trials, people with type 2 diabetes have tended to lose less weight on average than people without diabetes taking the same medicine. That pattern still doesn't tell you what any one person will experience.

What the trials show

The same medicines have been tested in separate trials for people with and without diabetes:

• Semaglutide 2.4 mg (Wegovy's dose): about 14.9% average weight loss at 68 weeks in adults without diabetes (STEP 1), versus about 9.6% in adults with type 2 diabetes (STEP 2). Placebo groups lost 2.4% and 3.4%.
• Tirzepatide (Zepbound/Mounjaro): up to about 20.9% at 72 weeks at the 15 mg dose in adults without diabetes (SURMOUNT-1), versus about 12.8% (10 mg) and 14.7% (15 mg) in adults with type 2 diabetes (SURMOUNT-2).

These were separate trials with different participants, so the comparison is indirect. But the direction is consistent, and a 2026 systematic review of low weight-loss response also lists diabetes-related factors, such as higher HbA1c and insulin resistance, among those associated with smaller weight loss.

Why diabetes status can matter

Proposed explanations overlap. Type 2 diabetes involves differences in insulin resistance and glucose regulation. Some diabetes treatments, including insulin and sulfonylureas, can promote weight gain. And as blood sugar comes under better control, the body loses fewer calories as glucose in the urine. None of these has been shown to be "the" reason for an individual, and the trials weren't designed to sort that out.

It also matters which trial you're reading. A head-to-head trial like SURMOUNT-5 (tirzepatide vs semaglutide) enrolled people with obesity without diabetes, so its results answer a different question from a diabetes trial comparing medicines for blood-sugar control. Results from different populations aren't interchangeable rankings.

Treatment goals may be broader than weight

For someone with type 2 diabetes, a clinician weighs blood glucose, heart and kidney risks, tolerability and other outcomes alongside weight. Some products have specific approved benefits for defined groups. In the US, for example, Ozempic is approved to lower the risk of major cardiovascular events in adults with type 2 diabetes and established heart disease, and to reduce the risk of sustained kidney-function decline, kidney failure and cardiovascular death in adults with type 2 diabetes and chronic kidney disease. Those claims belong to that product, its label and its country, not to every GLP-1. A weight-only comparison can miss the point of treatment. For a broader look, see what's known about GLP-1 medicines and diabetes complications.

Questions worth asking

Ask which outcome the medicine is meant to improve, how it'll be monitored, whether your other diabetes medicines affect the plan, and what happens if results differ from expectations. Don't adjust insulin or other diabetes medicines on your own because of weight-loss headlines: combining a GLP-1 with insulin or a sulfonylurea can raise the risk of low blood sugar, and your care team may need to adjust doses.

When you read GLP-1 news, check who was studied and what the trial was designed to answer. The fine print often explains why two results that seem to conflict can both be accurate.