Ozempic, Mounjaro, retatrutide, Wegovy, Saxenda… The market for peptide treatments against obesity is evolving so fast it is hard to keep up. But behind the brand names are really three key molecules: semaglutide, tirzepatide, and retatrutide. These three treatments share the same family of mechanisms, but their differences are significant — and can dramatically change your results.

The Same Family, Different Approaches

All three belong to the category of incretin receptor agonists. They mimic natural hormones produced by your body after meals to regulate appetite, blood sugar, and fat metabolism. The fundamental difference: the number of receptors they activate.

  • Semaglutide: GLP-1 agonist (one receptor)
  • Tirzepatide: GLP-1 + GIP agonist (two receptors)
  • Retatrutide: GLP-1 + GIP + glucagon agonist (three receptors)

Semaglutide: The Well-Established Pioneer

How It Works

Semaglutide mimics GLP-1, reducing appetite by signaling fullness to the brain, slowing stomach emptying, and reducing liver glucose production.

Clinical Results

The STEP 1 trial showed that with 2.4 mg semaglutide per week (Wegovy dose), participants lost an average of 14.9% of body weight over 68 weeks. About 1 in 3 participants lost more than 20%.

Availability in Canada

  • Ozempic (0.5–1 mg) — approved for type 2 diabetes
  • Wegovy (2.4 mg) — approved for obesity (BMI ≥ 30 or ≥ 27 with comorbidity)

Tirzepatide: The Dual Agonist Redefining Standards

How It Works

Tirzepatide, developed by Eli Lilly, combines GLP-1 and GIP actions. The combined effect of these two receptors produces a synergy that exceeds the simple addition of individual effects.

Clinical Results

SURMOUNT-1 trial data: at 15 mg per week, participants lost an average of 20.9% of body weight over 72 weeks. About 1 in 3 lost more than 25%, and nearly 1 in 5 lost more than 30%.

Availability in Canada

Available as Mounjaro, approved for type 2 diabetes. An obesity indication (Zepbound in the US) was under review at Health Canada in 2024–2025.

Retatrutide: The Triple Agonist Game-Changer

How It Works

Retatrutide adds glucagon receptor activation to GLP-1 and GIP. This increases basal energy expenditure and accelerates breakdown of stored fat, especially visceral fat.

Clinical Results

Phase 2 data published in the NEJM in June 2023 were described as “remarkable” by experts. At 12 mg per week, participants lost an average of 24.2% of body weight in just 48 weeks. Some subgroups showed losses of 30–35%.

Availability in Canada

Not yet available. Phase 3 TRIUMPH trials are ongoing. Approval expected around 2026–2027 if results are confirmed.

Full Comparison Table

Criterion Semaglutide Tirzepatide Retatrutide
Mechanism GLP-1 GLP-1 + GIP GLP-1 + GIP + Glucagon
Average weight loss ~15% ~21% ~24% (Ph.2)
Injection frequency Weekly Weekly Weekly
Available in Canada Yes Partial No (Ph.3)
Approved for obesity CA Yes (Wegovy) In review No
Clinical track record Long-term Medium-term Short (Ph.2)

How to Choose?

If you are starting medical treatment

Semaglutide has the most long-term clinical data and is the logical first step, especially if you also have type 2 diabetes or cardiovascular history.

If you want to maximize results available today

Tirzepatide produces superior weight loss compared to semaglutide. If your doctor determines you are a good candidate, it is often the best choice currently on the Canadian market.

Frequently Asked Questions

Can you switch from semaglutide to tirzepatide?

Yes, with medical supervision. No mandatory washout period exists between the two, but your doctor will adjust the protocol based on your tolerance.

Do these treatments work without changing your diet?

Technically yes, but that is not the recommended approach. These treatments work best long-term when integrated with dietary guidance and adapted physical activity. They reduce appetite, making those changes easier — but not replacing them.

Must these medications be taken for life?

Current data shows that stopping treatment generally leads to regaining a portion of lost weight. Since obesity is a chronic disease, long-term treatment — like for hypertension or cholesterol — is often considered.

Our Approach at Clinique Minceur

We evaluate each patient individually before recommending a treatment. What stage are you at? What is your history? Which treatments have you already tried? This — not the latest trend — guides our recommendation. Contact us for a consultation.