Fact-check: Stanford Medicine's three minutes on what the science says about GLP-1s

What the video covers

A short Stanford Medicine piece stitches together several faculty voices: obesity was, until recently, a common chronic disease with almost no effective drugs; the first GLP-1 was approved in 2005 so the class has two decades of use; the benefits reach blood sugar, heart, kidneys, liver and sleep apnoea; the common side effects are gastrointestinal; muscle loss is a concern patients raise; and weight bias makes people judge these side effects more harshly than they judge the side effects of drugs for other conditions.

What it gets right

The history is correct: exenatide was approved in April 2005. The list of benefits maps onto real trials and indications. Semaglutide reduced major cardiovascular events in SELECT (PubMed 37952131) and slowed kidney disease progression in FLOW, where the composite kidney outcome was 24 percent less frequent than with placebo (PubMed 38785209). Tirzepatide is approved for moderate to severe obstructive sleep apnoea in adults with obesity on the basis of SURMOUNT-OSA, which reduced the apnoea-hypopnoea index by about 25 to 29 events per hour against 5 to 6 on placebo (PubMed 38912654; Zepbound label). The side-effect list, nausea, diarrhoea, constipation and bloating, is the label's list.

The weight-bias argument is opinion, but it is a well-made one: the tolerance for adverse effects from blood-pressure or cancer drugs is much higher than the tolerance people show for GLP-1 side effects, and the video is explicit that this is a framing rather than a finding.

What it leaves out or overstates

One number needs correcting in the viewer's mind. A speaker says treatment cuts the risk of heart attack or stroke "by 30 or 50 percent depending on the treatment". The GLP-1 outcome trials do not support the upper end of that range. SELECT's hazard ratio for the primary composite was 0.80, a 20 percent relative reduction, and the absolute difference was 1.5 percentage points over about 40 months. SUSTAIN-6 in type 2 diabetes reported 26 percent. Bariatric surgery cohorts show larger relative reductions, and the speaker may have been including surgery, but the sentence as delivered will be heard as a claim about the drugs.

The muscle-loss reassurance ("if you look at their body composition before and after, it's actually improved") is clinical observation. Trial substudies with DXA show that roughly a quarter to a third of weight lost on semaglutide or tirzepatide is lean mass, while the proportion of the body that is lean mass rises. Both statements are true; the video gives only the reassuring half. The liver claim ("good for your liver") rests on MASH trial data for semaglutide that were still being reviewed for a label indication at the time of writing.

Where to go next

The NEJM and Cleveland Clinic clips in the semaglutide playlist give SELECT's actual numbers. The muscle question is covered on Weight Loss on GLP-1s, and the mechanism behind the kidney and heart findings on FormBlends Science. For plain-language outcome-trial digests, FormBlends Research. Compounded GLP-1s, including those FormBlends offers at formblends.com/products/tirzepatide, are not FDA approved and were not the products in these trials.