Semaglutide is sold as Ozempic and Wegovy. Tirzepatide is sold as Mounjaro and Zepbound. Beneath four brand names there are only two drugs, and this is what actually separates them.

Mechanism

Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual agonist: it engages GIP as well as GLP-1, a second gut-hormone receptor.

That second receptor is the leading explanation for why it tends to drive more weight loss in trials. It is not a small architectural difference.

Weight loss

Across the trial literature, tirzepatide generally produces more total loss — figures around twenty per cent and above at the top dose, against roughly fifteen for semaglutide.

Those are averages across populations, and individual results vary enormously around them. Both are far beyond anything the previous generation of weight medications managed, which is the more useful comparison for most people.

Side effects

Both share the same gastrointestinal profile — nausea, constipation, fatigue, the sulfur burps — and both are worst during titration.

Neither is clearly gentler for everyone. Which is why logging your own response beats reading forum anecdotes about somebody with a different gut.

What's the same — and what both miss

Both are weekly injections titrated over months. And both carry the same quiet risk: a considerable share of the weight lost can be lean mass if nothing is done about it.

So the protocol is identical either way. Log it, hit the protein, lift. Lean Protocol tracks both drugs and the compounded versions of them — dose, side effects, food tolerance, the trend that flags a stall, and the protein score that decides what the loss was made of. Lose the fat, keep the muscle, on either drug.

Educational, not medical advice — your prescriber chooses the right drug and dose for you.