A researcher's map of the incretin family — semaglutide, tirzepatide, retatrutide and the supporting cast — sorted by mechanism rather than hype, with a clear-eyed note on what the evidence supports.
The weight-loss peptide category is dominated by the incretin family, a group of molecules that share overlapping mechanisms but differ meaningfully in how many receptors they engage. This is a map of that landscape, organized by mechanism, so the differences actually make sense.
The GLP-1 baseline: semaglutide
Semaglutide is the reference point for the whole category. It is a single GLP-1 receptor agonist, and its research established the pattern the rest of the family builds on: influence on appetite signaling and glucose handling, delivered by a long-acting peptide. When people talk about "the shots," this is usually the mechanism they have in mind, even when the specific molecule is newer.
The dual agonists: tirzepatide
Tirzepatide adds a second receptor to the picture — GIP — alongside GLP-1. In clinical research, dual activation tended to produce larger average effects than single-receptor activation, which is why it became such a focal point. It represents the "add a receptor" strategy that defines the current generation of these compounds.
The triple agonist: retatrutide
Retatrutide is the leading triple agonist, engaging GLP-1, GIP, and glucagon. The glucagon component is the new element and is associated in research with energy expenditure rather than appetite alone. Early trial data has been notable, but retatrutide is still investigational — the most important word in this whole section. It is the frontier of the category, not a settled destination.
The supporting cast
Beyond the headline incretins, researchers study several smaller molecules in the fat-loss context. Tesamorelin and AOD-9604 are associated with different mechanisms tied to growth-hormone pathways and lipid metabolism, and MOTS-c is studied for its mitochondrial signaling role. These are not incretins and should not be lumped in with them; they represent separate research stories that happen to share a category label.
What the evidence actually supports
Here is the honest framing. The incretin compounds have the deepest clinical research behind them, and within that group more receptors has generally correlated with larger measured effects — at the cost of a different tolerability profile that researchers monitor closely. The supporting-cast molecules have thinner, more preliminary evidence. None of this is a recommendation, and none of these are approved products on this page; they are research compounds sold for laboratory use only.
How to think about the category
If you are trying to understand this space rather than shop it, sort by mechanism: how many receptors, and which ones. That single lens explains most of the differences between these molecules and cuts through the marketing that treats them all as interchangeable. The science is genuinely interesting on its own terms — it does not need the hype.
FOR LABORATORY RESEARCH USE ONLY — NOT FOR HUMAN OR VETERINARY USE. This content is educational and summarizes research literature; it is not medical advice or a product claim.