Medical Weight Loss With Semaglutide and Tirzepatide: What to Know Before You Start

GLP-1 medications like semaglutide and tirzepatide have changed the landscape of medical weight loss. The clinical data is significant. In the STEP 1 trial published in The New England Journal of Medicine, participants taking semaglutide 2.4 mg achieved an average weight loss of 14.9% of body weight over 68 weeks, with approximately 70% of participants losing at least 10% of their body weight.  (Source: Wilding)

Tirzepatide, which targets two hormone receptors instead of one, has shown even greater results. In the SURMOUNT-5 trial, the first head-to-head comparison of the two medications, tirzepatide produced an average weight loss of 20.2% compared to 13.7% with semaglutide over 72 weeks. Roughly 31.6% of patients on tirzepatide achieved at least 25% body weight loss compared to 16.1% on semaglutide. (Source: Aronne )

These aren't subtle results. They're in the range of what surgical interventions produce, without surgery. The demand for medical weight loss with semaglutide and tirzepatide has surged, and for good reason. But these are prescription medications that require medical supervision, proper dosing, and ongoing monitoring to be safe and effective. Where and how you access them matters.

How Semaglutide and Tirzepatide Work for Weight Loss

Both medications belong to a class of drugs called GLP-1 receptor agonists. They mimic a hormone your gut naturally releases after eating, which signals your brain to reduce appetite and slow digestion. The result is that you eat less, feel full longer, and your body begins to shift how it processes and stores energy.

Semaglutide (the active ingredient in Wegovy and Ozempic) activates GLP-1 receptors. Tirzepatide (the active ingredient in Mounjaro and Zepbound) is a dual agonist that activates both GLP-1 and GIP receptors, which appears to produce even greater effects on appetite regulation, fat metabolism, and blood sugar control. (Source: The SURMOUNT-5)

Both are administered as once-weekly injections with a gradual dose increase over the first several weeks. This slow titration helps minimize side effects and allows your body to adjust.

What to Expect on a Medical Weight Loss Program

Medical weight loss with semaglutide or tirzepatide is not a quick fix or a stand-alone solution. At Skin Fusion Spa, these medications are part of a supervised program that includes regular check-ins, dosage adjustments, and guidance on nutrition and lifestyle to support sustainable results.

Common side effects include nausea, decreased appetite (which is the mechanism working), and some GI adjustment during the first few weeks. In the SURMOUNT-5 trial, gastrointestinal side effects were the most commonly reported adverse events with both medications, and were mostly mild to moderate. Notably, GI-related treatment discontinuation was actually higher with semaglutide (5.6%) than tirzepatide (2.7%). (Source: ACC)

Results are gradual and cumulative. Most clients begin seeing meaningful changes within the first 4 to 8 weeks, with the most significant weight loss occurring over a 6 to 12 month period at therapeutic doses. Longer-term data from the STEP 5 trial showed that semaglutide maintained an average weight loss of 15.2% over 104 weeks, indicating that results are sustainable with continued use. (Source: Garvey WT)

Why Medical Supervision Matters for GLP-1 Weight Loss

The regulatory landscape around GLP-1 medications has shifted significantly. The FDA resolved the drug shortages for both semaglutide (February 2025) and tirzepatide (October 2024), which means the compounding loopholes that existed for the past couple of years have largely closed. The FDA is currently proposing to remove semaglutide and tirzepatide from the 503B bulks list entirely, with a comment period open through late June 2026. (Source: Orrick.)

What that means for consumers is that quality, sourcing, and prescriber oversight are more important than ever. At Skin Fusion, your medication is prescribed and monitored by a licensed medical provider. You're not buying medication from an unvetted online source with no follow-up. You're getting a supervised program with real accountability and medical oversight at every step.

Medical Weight Loss and Aesthetic Skin Concerns

One thing clients don't always anticipate is how rapid weight loss affects the skin. Loss of facial volume (sometimes referred to as "Ozempic face"), skin laxity, and changes in how the face and body look as fat deposits shift are all real considerations.

This is where being at a medspa has a genuine advantage. At Skin Fusion, we can address these aesthetic changes alongside your weight loss journey with treatments like dermal fillers for volume restoration, microneedling for skin tightening, and IV therapy to support nutrition and hydration during the process.

Medical weight loss with semaglutide and tirzepatide works best when it's part of a complete plan that accounts for both the medical and the aesthetic side of the transformation.

Ready to learn if GLP-1 medical weight loss is right for you? Book your consultation at Skin Fusion Spa.

Sources referenced in this post:

1. Wilding JPH, et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." The New England Journal of Medicine, 2021. nejm.org

2. Aronne LJ, et al. "SURMOUNT-5: Greater Loss of Weight, Waist Circumference With Tirzepatide Than Semaglutide." American College of Cardiology, 2025. acc.org

3. "Tirzepatide Demonstrates Superior Weight Loss to Semaglutide in 72-Week Phase IIIb SURMOUNT-5 Trial." Applied Clinical Trials, 2026. appliedclinicaltrialsonline.com

4. Garvey WT, et al. "Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial." Nature Medicine, 2022. ncbi.nlm.nih.gov

5. "FDA Moves to Shut the Door on Large-Scale Compounding of GLP-1 Drugs." Orrick, May 2026. orrick.com