GLP-1 receptor agonists mimic a gut hormone — but more strongly and for much longer than the natural version. The result is coordinated effects on blood sugar, appetite, gastric emptying, and brain reward systems.
The native GLP-1 hormone
When you eat, intestinal cells release GLP-1 within minutes. The natural hormone is broken down by DPP-4 within 1–2 minutes. In that window: pancreatic insulin release (glucose-dependent), glucagon suppression, slowed gastric emptying, and satiety signaling.
What the agonists do
Engineered to resist DPP-4 breakdown. Semaglutide has a half-life of ~7 days, enabling weekly dosing. The signal that GLP-1 would normally send for minutes is now sustained continuously.
The four mechanisms
- Glucose-dependent insulin secretion. Beta-cells release insulin in response to elevated glucose — why GLP-1 alone doesn't cause hypoglycemia.
- Glucagon suppression. Postprandial glucagon (which raises blood sugar) is reduced.
- Slowed gastric emptying. Food moves more slowly — flattening glucose response and increasing satiety.
- Central appetite effects. Hypothalamic and reward-system effects — patients describe 'food noise quieting.'
Downstream cardiometabolic effects
Direct vascular endothelium and myocardium effects (SELECT). Reduced glomerular hyperfiltration (FLOW). Improved insulin sensitivity. Reduced lipogenesis.
What it doesn't do
- Preserve muscle. Resistance training + protein do.
- Repair prior damage. Time and behavior change do.
- Work after stopping. Discontinuation produces regain (STEP-4).