Chapter 7
GLP-1 Deep Dive
7.1 What GLP-1s Really Are
GLP-1 stands for Glucagon-like Peptide-1. It's a hormone your gut naturally produces in response to food.
What does it do?
- Increases insulin secretion to manage blood sugar
- Slows gastric emptying, keeping you fuller longer
- Suppresses appetite through the brain's hypothalamus
Drugs like Semaglutide are synthetic versions of this hormone — designed to amplify your body's satiety and glucose management systems.
7.2 The Metabolic Code (GLP-1 / GIP / Glucagon)
When your metabolism is healthy, three hormones work together in rhythm:
1. GLP-1
Lowers blood sugar, reduces appetite, slows digestion
2. GIP (Gastric Inhibitory Polypeptide)
Enhances fat storage and insulin sensitivity
3. Glucagon
Maintains blood glucose during fasting and stimulates fat breakdown
| Drug | Receptors Targeted | Key Effects |
|---|---|---|
| Semaglutide | GLP-1 only | Appetite ↓, insulin ↑, digestion slower |
| Tirzepatide | GLP-1 + GIP | + fat metabolism ↑, insulin sensitivity ↑ |
| Retatrutide | GLP-1 + GIP + Glucagon | + metabolic rate ↑, fat burning high |
7.3 The 5 GLP Compounds
1. Tirzepatide
AKA: Mounjaro, LY3298176
Dual GLP-1 + GIP receptor agonist. Enhancing insulin response, slowing gastric emptying, reducing appetite.
Tirzepatide ↗2. Retatrutide
AKA: LY3437943
Triple agonist – GLP-1 + GIP + Glucagon receptors. Increased thermogenesis, improved insulin sensitivity, accelerated body recomposition.
Retatrutide ↗3. Mazdutide
AKA: IBI362
Dual GLP-1 + Glucagon receptor agonist. Liver fat reduction, body weight modulation, improved metabolic markers.
Mazdutide4. Survodutide
Dual GLP-1 + Glucagon receptor agonist. Hepatic fat clearance, weight reduction, appetite signaling.
Survodutide ↗5. Semaglutide
AKA: Ozempic, Wegovy
GLP-1 receptor agonist. Appetite suppression, insulin regulation, glycemic control. Most studied peptide in GLP-1 category.
Semaglutide ↗Featured GLP-1 Research Compounds
Retatrutide
Triple agonist
View ProductTirzepatide
Dual agonist
View ProductSemaglutide
GLP-1 agonist
View ProductTesofensine
Appetite suppressant
7.4 FAQ — GLP-1
What is the difference between semaglutide, tirzepatide and retatrutide?
Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual GLP-1/GIP agonist. Retatrutide is a triple GLP-1/GIP/glucagon agonist. The more targets engaged, the more pronounced the metabolic effects observed in research.
Do GLP-1s only act on appetite?
No. They slow gastric emptying, modulate satiety signaling in the brain and promote glucose-dependent insulin secretion. The effect on appetite is only part of the mechanism.
Why always start at a low dose?
Gradual titration reduces the gastrointestinal effects (nausea, discomfort) common at the start of use. It is a standard practice documented in clinical studies.
Do effects persist after stopping?
Available data show that part of the metabolic effect tends to fade after discontinuation. Durability depends heavily on lifestyle habits maintained afterwards.
Scientific references
- Drucker DJ. Mechanisms of action and therapeutic application of glucagon-like peptide-1. Cell Metabolism. 2018;27(4):740-756. doi:10.1016/j.cmet.2018.03.001 · PMID 29617641
- Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine. 2021;384(11):989-1002. doi:10.1056/NEJMoa2032183 · PMID 33567185
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038 · PMID 35658024