Tirzepatide
Tirzepatide is a dual GIP/GLP-1 receptor agonist originally developed for type 2 diabetes that has demonstrated exceptional weight loss results — up to 22% body weight reduction in clinical trials. It acts on two complementary hormonal pathways to suppress appetite and improve metabolic function.
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Tirzepatide (brand name Mounjaro/Zepbound) is a once-weekly injectable peptide that targets both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptors simultaneously. This dual mechanism sets it apart from earlier GLP-1-only agents.
In the SURMOUNT-1 trial, participants without diabetes achieved an average weight loss of 20.9% of body weight at the highest dose (15 mg/week) over 72 weeks — results previously achievable only through bariatric surgery.
The compound works by slowing gastric emptying, increasing satiety signals, reducing appetite, and improving insulin sensitivity. The GIP component appears to enhance the GLP-1 effects while reducing some side effects like nausea.
Dosing Reference
| Beginner Dose | 2.5 mg/week |
| Standard Dose | 5–10 mg/week |
| Advanced Dose | 12.5–15 mg/week |
| Frequency | Once weekly subcutaneous injection |
| Cycle Duration | 12–72 weeks (ongoing for maintenance) |
Note: Always titrate slowly. Start at 2.5 mg for 4 weeks minimum before increasing. Rapid dose escalation significantly increases nausea and GI side effects.
Mechanism of Action
Tirzepatide activates both GIP and GLP-1 receptors in the pancreas, brain, gut, and adipose tissue. GLP-1 receptor activation suppresses glucagon secretion, slows gastric emptying, and signals satiety in the hypothalamus. GIP receptor activation complements this by enhancing insulin secretion and may improve the tolerability profile.
The combined receptor activation produces greater weight loss than GLP-1 agonism alone, suggesting synergistic effects on energy homeostasis.
Side Effects
| Effect | Severity |
|---|---|
| Nausea | moderate |
| Vomiting | mild |
| Diarrhea | mild |
| Constipation | mild |
| Injection site reactions | mild |
| Hypoglycemia (in non-diabetics) | mild |
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