Semaglutide: weight, heart and kidney outcomes

SELECT: adults without diabetes

Semaglutide's SELECT trial enrolled 17,604 adults with established cardiovascular disease and overweight or obesity, without diabetes. Treatment reduced the combined outcome of cardiovascular death, nonfatal heart attack or nonfatal stroke compared with placebo.

I trust SELECT's event comparison to answer a concrete clinical question. It supplies an answer beyond a plausible explanation of how a drug works. Its reach is also concrete: these participants already had cardiovascular disease.

It would be tempting to turn SELECT into a simple tale about weight loss protecting the heart. The trial result establishes the event difference in the tested group; assigning that difference entirely to weight loss asks a further causal question. The finding is compelling enough without that extra claim.

STEP 1

In STEP 1, adults with overweight or obesity and without diabetes had an average body-weight change of -14.9% with semaglutide and -2.4% with placebo at 68 weeks. Both the population and the time point travel with those figures.

The difference is substantial. I want STEP 1's placebo result in the same frame: without the comparison, a treatment-arm percentage loses some of its meaning. Neither average predicts an individual's weight change.

SURMOUNT-5: semaglutide versus tirzepatide

SURMOUNT-5 compared semaglutide with tirzepatide in 751 adults with obesity. At 72 weeks, average body-weight change was -13.7% with semaglutide and -20.2% with tirzepatide.

The semaglutide figure differs from STEP 1's figure because these are separate trials. For the comparison between those two medicines, SURMOUNT-5 carries more weight than assembling percentages from unrelated studies. It still addresses weight change in that trial, leaving the heart and kidney questions to their own studies.

GLP-1 and the FLOW kidney trial

Semaglutide mimics GLP-1. It promotes insulin release when blood sugar is higher, reduces glucagon release, slows stomach emptying and changes appetite. The safety review discusses this pharmacology alongside clinical harms. Tablets and injections contain the same active molecule, while the formulation and route require their own evidence.

FLOW studied 3,533 people with type 2 diabetes and chronic kidney disease. Semaglutide reduced major kidney-disease events compared with placebo. The trial's combined outcome included kidney failure, a substantial decline in kidney filtration, and kidney or cardiovascular death.

That is a different group from SELECT's. Put together, the trials show why I resist reducing semaglutide to its reputation for suppressing appetite: meaningful clinical outcomes have been tested in distinct disease settings.

Digestive effects and patient accounts

The 2021 safety review reported nausea in roughly one-third of patients. Gastrointestinal effects were mostly mild-to-moderate and transient; biliary disease, including gallstones, occurred more often. The review judged the overall benefit-risk profile favourable in type 2 diabetes.

Thyroid C-cell tumours in animal studies underlie the thyroid warning. Human thyroid and pancreatic cancers were too uncommon for the review to draw definitive conclusions. Rapid improvement in blood sugar can also worsen existing diabetes-related eye damage. A good cardiovascular result has to coexist with these safety questions.

People describe quieter food cravings, earlier fullness, reflux, bowel changes, fatigue and hair shedding during weight loss. Those are anecdotal accounts rather than clinical evidence. They give language to experiences; they cannot establish how often semaglutide caused a particular problem.

Approved semaglutide products require a prescription. A familiar compound name on other material cannot establish matching contents or pharmaceutical quality.