Skip to content
This GLP
← Research
Evidence

BMI thresholds: the cut-off you qualify under is a convention

A trial in China and Taiwan enrolled people at a BMI of 24 to 30, below where the Western trials start. The cut-off you meet or miss is a guideline, not a boundary in a body.

Glenn Torres5 min read
Body mass index at trial entrySTEP 12 entry (China, Taiwan)typical Western trial entry242730

Every intake form in this market asks for a height and a weight, and somewhere behind it sits a number that decides whether you are offered anything at all. That number is not a fact about bodies. It is a guideline, and guidelines differ — which is a different kind of gate from the state lists sellers publish but works the same way.

A trial run at lower numbers

STEP 12 enrolled adults across 19 sites in mainland China and Taiwan using locally defined BMI thresholds: 24 to under 28 with at least one weight-related condition, or 28 to under 30 with or without type 2 diabetes. [1] Of 242 participants, 161 received semaglutide 2.4 mg weekly and 81 placebo, for 44 weeks, alongside lifestyle intervention. Half were women and 19.4% had type 2 diabetes.

Those entry criteria sit below where the well-known trials began. The rationale is not novel and it is not this desk’s: East Asian guidelines set overweight and obesity cut-points lower because cardiometabolic risk rises at lower BMI in these populations. The trial was designed around the local definition rather than the American one.

What it found

Body weight fell 12.1% on semaglutide against 2.2% on placebo — an estimated treatment difference of 9.9 percentage points, 95% CI −11.8 to −8.0, p<0.0001. The proportion reaching at least 5% weight loss was 80.5% against 24.4%, an odds ratio of 14.8, 95% CI 7.4 to 29.6.

Adverse events were reported by 141 of 161 participants on the drug, 87.6%, and 61 of 81 on placebo, 75.3%. Both figures are high, and the difference between them is smaller than the drug figure alone suggests — which is the reason to always ask what the placebo arm reported.

How it compares

The 12.1% reduction is smaller than the headline figures from the large Western trials, and the honest comparison is not straightforward. This cohort started at a lower BMI, so there was less weight available to lose, and the trial ran 44 weeks rather than 68. Weight loss expressed as a percentage behaves differently depending on where you start, which is one reason expected-loss estimates should never be read as a promise.

What does travel is the shape: a large, clearly significant separation from placebo on both co-primary endpoints, consistent with what the wider trial evidence shows. A drug that works only in the populations it was first tested in would be the surprising result, and this is not that.

Why a single trial in one region matters here

Because most readers meet this drug through a corpus of trials conducted largely in the United States and Europe, and the generalization outward is usually assumed rather than demonstrated. Trials like this one are how the assumption gets tested, and they tend to arrive years later and attract a fraction of the attention.

It is also a reminder that the published evidence is narrower than the marketing implies at any given moment — the same gap that separates a famous trial from the literature behind it. The trial was funded by Novo Nordisk, which makes the drug.

Frequently asked

Why did this trial enroll people at a lower BMI?
It used locally defined thresholds. East Asian guidelines set overweight and obesity cut-points lower because cardiometabolic risk rises at lower BMI in these populations, and the trial was designed around that definition.
Does that mean I qualify at a lower BMI?
No. A trial run under one country's guidelines does not change the criteria a prescriber elsewhere works to, and nothing here is a reason to describe yourself differently on an intake form.
Why was the weight loss smaller than in the famous trials?
Participants started at a lower BMI, so there was less weight available to lose, and the trial ran 44 weeks rather than 68. Percentage weight loss is not comparable across different starting points.
Were side effects worse?
Adverse events were reported by 87.6% on semaglutide and 75.3% on placebo. Both are high, and the gap is narrower than the drug figure alone suggests.

Sources

  1. [1] Guo L, et al. (2026). Efficacy and safety of once-weekly semaglutide 2·4 mg in Chinese adults with overweight or obesity (STEP 12): a randomised, double-blind, placebo-controlled, multicentre, phase 3b trial The Lancet Diabetes & Endocrinology. PMID 42575111

Where to get it

Best GLP-1 injections

Every injectable seller we can verify, with the price each one publishes and an honest read of what the trials measured.

Compare providers →

More in Evidence