What is GLP-1s?
Semaglutide (Ozempic/Wegovy), tirzepatide (Mounjaro/Zepbound), and related peptides.
GLP-1 receptor agonists mimic the incretin hormone GLP-1, which is released after eating. They slow gastric emptying (food stays in stomach longer), reduce appetite at the brain level by acting on hypothalamic hunger centers, and improve insulin sensitivity. Semaglutide users typically report dramatically reduced food noise - the constant thoughts about food disappear. Most people lose 15-20% of body weight over 12-18 months. Tirzepatide (dual GIP/GLP-1 agonist) shows even stronger results in trials, with some users losing 20-25% body weight. These are the most effective weight loss medications ever developed. Common side effects include nausea (usually fades after 4-8 weeks), constipation, and reduced appetite. Rare but serious risks include pancreatitis and gallbladder issues. Muscle loss is a concern - protein intake and resistance training are critical while using these medications.
What the evidence says
The overall evidence grade for GLP-1s is A (strong — consistent, high-quality human evidence (systematic reviews, well-powered RCTs)). FDA approved with extensive Phase 3 trials. STEP and SURMOUNT trials showed 15-22% weight loss.
Specific findings with supporting evidence:
- Average 15-20% body weight loss with semaglutide. Evidence grade A.
- Average 20-25% weight loss with tirzepatide. Evidence grade A.
- Significantly reduces cardiovascular events in at-risk patients. Evidence grade A.
- Reduces food cravings and appetite. Evidence grade A.
Best-supported outcomes:
- Substantial weight loss.
- Improved glycemic control.
- Reduced cardiovascular risk.
- Decreased food preoccupation.
Where marketing outpaces evidence:
- Marketing often overstates: Works without any lifestyle changes.
- Marketing often overstates: No muscle loss concerns.
- Marketing often overstates: Can stop anytime without regain.
Dose and timing
Take it in the morning. Weekly injection; same day each week.
Who it's for, and who should skip it
Most relevant for:
- Those with BMI 30+ or 27+ with comorbidities.
- Type 2 diabetics.
- Those who have failed diet/exercise alone.
Not appropriate for:
- History of medullary thyroid cancer or MEN2.
- History of pancreatitis.
- Pregnant or planning pregnancy.
Safety and cautions
Caution: Muscle loss. High protein intake (1g/lb) and resistance training essential to preserve muscle. GI adaptation. Nausea common first 4-8 weeks; eating slowly and smaller portions helps. Caution: Weight regain. Most regain weight after stopping; may need long-term use.
Common mistakes
- Not eating enough protein.
- Skipping resistance training.
- Titrating up too fast.
- Using compounded versions of unknown quality.
Myths vs reality
A common misconception: GLP-1s are just for lazy people. In reality, they correct biological dysregulation of hunger/satiety signals that diet alone cannot fix. A common misconception: You will lose only fat. In reality, up to 40% of weight loss can be muscle without proper protein and training.
How it interacts with other compounds
- GLP-1s works well alongside retatrutide — next-generation triple agonist in trials.
Questions people ask
What is "food noise"? The constant mental preoccupation with food that many people experience. GLP-1s dramatically reduce or eliminate this.
Will I regain weight if I stop? Studies show most people regain 2/3 of lost weight within a year of stopping. Many need ongoing treatment.
Ozempic vs Wegovy vs Mounjaro? Ozempic and Wegovy are both semaglutide (different doses/indications). Mounjaro (tirzepatide) is a dual agonist with potentially stronger effects.
Editorial note
This guide summarizes the published evidence on GLP-1s. It is educational content, not medical advice. Confirm with your clinician if you take prescription medications or manage a chronic condition.