This one has a reasonably settled answer, so here it is. The mechanism is slowed transit plus reduced intake, and that combination determines which interventions work. Less food means less bulk, slower motility means more water reabsorbed, and the result is a smaller, drier, slower stool. Insoluble fiber adds bulk to a system that is already moving slowly, which is why it frequently makes things worse. Soluble fiber holds water and is the better first choice, and an osmotic agent works with the mechanism rather than against it.

Dr.NutriCornell said:

The mechanism is slowed transit plus reduced intake, and that combination determines which interventions work.

Gastric emptying studies and constipation: semaglutide delays gastric emptying by ~40% at steady state, as measured by acetaminophen absorption testing and scintigraphy[1].

Clinically relevant implications:

• Explains early satiety and nausea
• Affects absorption of co-administered oral medications
• Creates aspiration risk for procedures under anesthesia
• Contributes to constipation via slowed GI transit

Importantly, the gastric emptying delay attenuates with continued use (tachyphylaxis), which correlates with the transient nature of GI side effects.

mia_MS2 said:

Constipation replaced nausea at around week five and has been the more persistent of the two by a wide margin.

Same position here, arrived at the long way round. The escalation order that reflects the mechanism: water and salt first, then soluble fiber, then magnesium or an osmotic agent, then a stimulant only briefly and only if the osmotic has failed. Stimulants first is the commonest error and the one most likely to end in a cycle of dependence.

Adding the clinical framing, because it changes how the question reads.

Sulfur burps on constipation — the most underrated side effect nobody warned me about. 🤢 The smell is absolutely vile and comes on without warning.

What finally helped: taking a digestive enzyme supplement. Also, eating smaller portions and chewing thoroughly reduces the gas production.

If sulfur burps persist beyond 2-3 weeks, talk to your provider — it could indicate gastroparesis that needs medical attention.