GLP-1 Agonists: How Incretins Reduce Weight

GLP-1 is a hormone your gut releases after eating. It tells the pancreas to release insulin, slows the stomach, and signals the brain "stop eating." Synthetic analogs do the same thing, but stronger and longer. Here's how it works at the biology level.

Where GLP-1 comes from

L-cells in the small intestine release GLP-1 in response to food. Natural GLP-1 has a half-life of about 2 minutes since DPP-4 enzyme destroys it almost instantly. Synthetic analogs are modified so DPP-4 can't break them down, extending action to days.

Three weight loss mechanisms

Stomach slowing. GLP-1 delays gastric emptying. Food stays in the stomach longer, you feel full longer. Mechanical effect.

Brain signaling. GLP-1 receptors exist in the hypothalamus and brainstem. Activation reduces eating motivation, decreases food reward, suppresses cravings.

Insulin and glucagon. GLP-1 enhances glucose-dependent insulin secretion and suppresses glucagon. Result: better sugar control, fewer insulin spikes, less fat storage.

Evolution: one receptor to three

Semaglutide: GLP-1 only. [[Tirzepatide|10]]: GLP-1 + GIP (dual agonist, Phase III, 22.5% weight loss). [[Retatrutide|11]]: GLP-1 + GIP + glucagon (triple, Phase II, 24% weight loss). Each generation adds a new receptor and mechanism.

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This article is for educational purposes. Peptides are intended for research use. Consult a healthcare professional before starting any protocol.