Fatigue on semaglutide — caloric deficit vs direct drug effect

Answering the narrow version, because the broad one does not have a single answer. The mechanism that matters here is not stomach emptying, it is central. GLP-1 receptor agonism in the arcuate nucleus stimulates POMC neurons and suppresses AgRP/NPY signalling, which is why the effect is appetite and food salience rather than physical fullness. Delayed gastric emptying largely tachyphylaxes over the first months; the appetite effect does not.

Dr.NateNeph said:

The mechanism that matters here is not stomach emptying, it is central.

That is correct as far as it goes, and here is where it stops going. Albumin binding above 99% is the whole reason weekly dosing works, and it is also why the trough matters more than the peak. People who dose late are not losing a peak, they are letting the trough fall, and the appetite effect tracks the trough.

SleepFixSam said:

Started at 0.25mg with a fairly bad first week, held each step the full four weeks, and I am now at 1mg with no side effects worth naming.

All true, with one condition: that curve is for people who reached the dose on schedule. Anyone who slowed the ladder for tolerability is on a different, flatter curve, and comparing yourself with the published mean will make you feel like a non-responder when you are not.

Clinical perspective, offered as context rather than as advice.

SleepFixSam said:

...but the FDA says semaglutide...

Interesting point. I want to add some regulatory nuance: the FDA labeling reflects the specific clinical trial data submitted for approval. Real-world clinical practice often extends beyond the FDA label based on emerging evidence and clinical judgment.

Example: semaglutide was first approved for diabetes (Ozempic), then obesity (Wegovy). The molecule didn't change — our understanding of its applications expanded. Similarly, semaglutide may evolve as more data accumulates.