How much weight can you lose with GLP-1 treatment?

The numbers people usually see online

One of the most quoted semaglutide trials is STEP 1. Adults with overweight or obesity without diabetes received semaglutide 2.4 mg or placebo alongside lifestyle intervention for 68 weeks. Average body-weight change was about -14.9% with semaglutide versus -2.4% with placebo.

In the 72-week SURMOUNT-5 head-to-head obesity trial, average weight change was about -20.2% with tirzepatide and -13.7% with semaglutide. These are group averages measured under trial conditions.

Why your result may be different

A patient does not enter treatment as an 'average'. Starting weight, metabolic disease, medication tolerance, dose reached, nutrition, physical activity, sleep and adherence all influence the trajectory.

Some people respond earlier or more strongly; some lose weight more gradually; and some do not achieve enough benefit to justify continuing a particular treatment.

Time matters

Headline percentages are usually measured after many months, often more than a year. Comparing your first eight or twelve weeks with a 68- or 72-week trial result creates unrealistic expectations.

Early treatment also includes dose escalation. The aim is not to rush to the maximum dose but to build a tolerable and clinically appropriate plan.

Do not judge progress by kilograms alone

Body weight is important, but it is only one outcome. Waist circumference, glycaemic control, blood pressure, lipids, physical function and how sustainable the patient's eating and activity patterns are may also matter.

That broader view is particularly relevant when the reason for treatment is metabolic health rather than appearance.

A better benchmark

Instead of asking, 'Will I lose 20%?', ask: Is the treatment producing clinically meaningful progress for me? Am I tolerating it? Are my health markers moving in the right direction? And is the plan sustainable?

Those questions turn a headline statistic into an individual medical decision.

References

• Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. 2021. PubMed

• Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. 2025. PubMed

• Lincoff AM, et al. Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial. Nature Medicine. 2024.

Written and clinically reviewed by: Dr Saran Seker, MBBS (Aus), Chief Medical Officer

Last reviewed: September 2026