Collecting this in one place because it comes up every few weeks and the answer is always assembled from scratch. It is about the glucagon co-agonists, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
The glucagon co-agonists — survodutide, mazdutide, ecnoglutide — are all chasing the same idea: add energy expenditure to appetite suppression. The liver signal is where they look strongest, because hepatic fatty-acid oxidation responds to glucagon directly rather than as a consequence of weight loss.
The condition it depends on
Worth remembering these are at different regulatory stages in different regions, and a phase 2 result in one jurisdiction is being quoted here as if it were a global standard of care.
What I am not sure about
What would genuinely help is knowing whether the liver signal is independent of weight loss or downstream of it, because that determines whether any of this is interesting for someone whose weight is already where they want it. Practical detail welcome, however dull — the duller the better.
gary_naperville said:The glucagon co-agonists — survodutide, mazdutide, ecnoglutide — are all chasing the same idea: add energy expenditure to appetite suppression.
Agreed, and the adaptation point cuts both ways: tachyphylaxis to gastric emptying is why tolerability improves, and it is also why people who were relying on physical fullness feel the effect fade while the appetite effect is still working.
gary_naperville said:The glucagon co-agonists — survodutide, mazdutide, ecnoglutide — are all chasing the same idea: add energy expenditure to appetite suppression.
Glucagon receptor pharmacology in triple agonists (retatrutide), relevant to the glucagon co-agonists: the glucagon component is the most controversial because glucagon traditionally raises blood glucose. So why include it in an anti-obesity drug?
Key insight: glucagon increases energy expenditure (thermogenesis), promotes hepatic lipid oxidation, and reduces appetite through distinct CNS mechanisms. The hyperglycemic effect is counterbalanced by the GLP-1 component's insulin secretagogue action.
Net result: more weight loss through increased expenditure (glucagon) + decreased intake (GLP-1/GIP), with neutral or improved glycemia. An elegant pharmacological balancing act[1].
[1] Day JW, et al. Nat Rev Drug Discov. 2022;21:37-54.
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View ResultsShort answer first, then the reasoning. The mechanism is more central than most summaries suggest. Receptor agonism in the arcuate nucleus activates POMC neurons and inhibits AgRP/NPY signalling, and the downstream MC4R pathway is the same one disrupted in monogenic obesity — convergent genetic evidence that the target is the right one. Peripherally there is glucose-dependent insulin secretion, glucagon suppression and delayed gastric emptying, but the gastric component largely adapts over months while the central effect persists, which is why the durable effect is appetite rather than fullness.
Dr.SportsMedIN said:Agreed, and the adaptation point cuts both ways: tachyphylaxis to gastric emptying is why tolerability improves, and it is also why people who were…
Can confirm. Same sequence, different timescale. I had assumed I was the exception until I read this.