GLP-1 Agonists Guide
Complete resource for understanding and using GLP-1 receptor agonists for weight management
Download PeptideFox on the App StoreWhat Are GLP-1 Agonists?
GLP-1 (glucagon-like peptide-1) agonists are a class of medications that mimic a natural gut hormone released after eating. They work through multiple mechanisms: slowing stomach emptying so you feel full longer, reducing appetite signals in the brain, and improving how your body handles blood sugar.
Originally developed for type 2 diabetes, these medications have become the most effective pharmaceutical option for weight loss, with clinical trials showing sustained weight loss of 15-25% of body weight over 12-18 months. The three main compounds available today differ in how many hormone receptors they activate and their resulting effects.
GLP-1 Compounds at a Glance
| Compound | Brand Names | Mechanism | Avg. Weight Loss | Status |
|---|---|---|---|---|
| Semaglutide | Ozempic, Wegovy | GLP-1 Receptor Activation | 12–15% | 🟢 FDA Approved |
| Tirzepatide | Mounjaro, Zepbound | Dual GIP/GLP-1 Receptor Activation | 18–21% | 🟢 FDA Approved |
| Retatrutide | Investigational (Phase 2) | Triple Agonist: GLP-1 / GIP / Glucagon | 22–24% | 🟡 Phase 3 Ongoing |
Explore GLP-1 Tools & Guides
Compare Compounds
Side-by-side comparison of semaglutide, tirzepatide, and retatrutide with trial data and dosing protocols.
ExploreDose Frequency & Titration Optimizer
Interactive tool to simulate dose escalation schedules and visualize plasma curves.
CalculateBuild Protocol
Step-by-step wizard to create a personalized GLP-1 protocol with support stack.
StartSupport Stacks for GLP-1s
How to preserve lean mass during GLP-1 therapy with targeted peptide and nutrition support.
Read guideRetatrutide: Advanced Stack
Dual-axis protocol to protect lean mass while maximizing fat loss on retatrutide.
Read guideExplore All GLP-1 Content
Deep dives, practical protocols, and clinical guidance across all GLP-1 topics.
Browse allFrequently Asked Questions
What are GLP-1 agonists and how do they work?
GLP-1 (glucagon-like peptide-1) agonists mimic a gut hormone that regulates appetite and blood sugar. They slow gastric emptying, reduce hunger signals to the brain, and improve insulin sensitivity. This leads to reduced calorie intake and weight loss of 15-25% of body weight in clinical trials.
What is the difference between semaglutide, tirzepatide, and retatrutide?
Semaglutide (Ozempic/Wegovy) is a GLP-1 single agonist, the most studied with ~15% weight loss. Tirzepatide (Mounjaro/Zepbound) is a dual GIP/GLP-1 agonist achieving ~21% weight loss. Retatrutide is a triple agonist (GLP-1/GIP/glucagon) currently in Phase 3 trials showing up to 24% weight loss.
Which GLP-1 medication causes the most weight loss?
In clinical trials, retatrutide showed the highest weight loss at 24% at 48 weeks, followed by tirzepatide at 21% (SURMOUNT-1) and semaglutide at 15% (STEP-1). However, retatrutide is still investigational while semaglutide and tirzepatide are FDA-approved.
How long does it take to see results from GLP-1 medications?
Most people notice reduced appetite within the first week. Weight loss typically begins in weeks 2-4. By week 8-12, users commonly see 5-10% weight loss. Maximum effects usually occur at 16-20 weeks on maintenance dose, with continued gradual loss through 68-72 weeks.
What are common side effects of GLP-1 agonists?
The most common side effects are gastrointestinal: nausea (affects 20-40%), vomiting, diarrhea, and constipation. These typically decrease after the first few weeks as the body adjusts. Slow dose escalation reduces side effect severity. Serious but rare risks include pancreatitis and gallbladder issues.
Can I take GLP-1 medications if I have type 2 diabetes?
Yes. GLP-1 agonists were originally developed for type 2 diabetes. Semaglutide (Ozempic) and tirzepatide (Mounjaro) are FDA-approved for diabetes management. They improve HbA1c levels by 1-2% while also promoting weight loss, making them particularly effective for diabetic patients with obesity.
How do I prevent muscle loss while taking GLP-1 medications?
The key is combining GLP-1 therapy with resistance training 2-4x weekly and high protein intake (1.6-2.2g per kg body weight). Studies show 30-40% of weight lost on GLP-1s can be lean mass without exercise. With proper training and nutrition, users maintain most muscle while losing primarily fat.
Medical Disclaimer
The content in this GLP-1 guide is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before beginning any new protocol, supplement, or medication.