STEP 3: semaglutide added to intensive behavioural therapy

Why this study matters

Most weight-management trials give people a modest amount of lifestyle support. STEP 3 asked a different question: what happens when semaglutide (Wegovy, Ozempic) is added to a much more intensive program of counselling and diet? This matters for Canadian readers because it shows two things at once. It shows how much weight people lost with intensive behavioural support alone, and how much more they lost when the medicine was added.

Who was in the study

The trial enrolled 611 adults at 41 sites in the United States, between August 2018 and April 2020. No one had diabetes. Everyone had either overweight with a body mass index (BMI) of 27 or higher plus at least one weight-related condition, or obesity with a BMI of 30 or higher. BMI is a number that compares weight with height.

Most participants were women (495 people, or 81.0%). The average age was 46 years. Average body weight at the start was 105.8 kg, and average BMI was 38.0. The trial ran for 68 weeks.

What the researchers did

This was a randomized, double-blind, parallel-group trial. Randomized means chance decided who got which treatment. Double-blind means neither the participants nor the study staff knew who got the medicine. A placebo is an injection that looks the same but contains no active medicine.

For every two people assigned to semaglutide, one was assigned to placebo. In total, 407 people received semaglutide 2.4 mg once a week by injection under the skin, and 204 received placebo.

Both groups received the same intensive behavioural therapy. This included a low-calorie diet for the first 8 weeks and 30 counselling visits spread across the 68 weeks.

The main results were the percentage change in body weight and the share of people who lost at least 5% of their starting weight by week 68. The trial also looked at losses of at least 10% and at least 15%.

What they found

At week 68, average body weight had changed by -16.0% in the semaglutide group and by -5.7% in the placebo group (R32-C05). The difference was -10.3 percentage points, with a 95% confidence interval of -12.0 to -8.6. A confidence interval is the range in which the true difference is likely to sit. The whole range is below zero, so the added benefit of the medicine was clear.

Note that almost half of the placebo group lost at least 5% of their weight with the behavioural program alone.

Of the 611 people randomized, 567 (92.8%) completed the trial, and 505 (82.7%) were still receiving their assigned treatment at the end.

Side effects and people who stopped

Gastrointestinal (stomach and bowel) side effects were more common with semaglutide, reported by 82.8% of people in that group compared with 63.2% in the placebo group (R32-C06). Treatment was stopped because of these events in 3.4% of people on semaglutide and 0% of people on placebo.

The summary we reviewed does not report the overall rate of stopping for all side effects combined, or the specific types of gastrointestinal events.

What this study does not tell you

• Our summary is based on the abstract and extracted data. Two attempts to retrieve the full paper were unsuccessful.
• Both groups received intensive behavioural therapy, so the results show what semaglutide adds to that program. The trial cannot separate the effect of the diet from the effect of the counselling.
• The 30 counselling visits are far more support than most people receive in routine care, so the placebo group's result may not reflect what usual care achieves.
• All sites were in the United States, and people with diabetes were excluded.
• The trial lasted 68 weeks. The authors say more research is needed to know whether the results last.
• The summary we reviewed does not state who funded the trial or the authors' conflicts of interest.

What it means in Canada

STEP 3 shows that intensive behavioural support led to meaningful weight loss on its own, and that semaglutide added more on top of it. The kind of program used here, with 30 visits and a starting low-calorie diet, is not what most Canadians are offered. For how the medicine is used in Canada, see semaglutide in Canada. For questions about what provincial plans pay for, see public drug coverage by province. To look at care options that include behavioural support, see compare services.

Related reading

Other studies in this library that bear on the same question.

Source