GLP-1 & Weight Loss

Mounjaro, Ozempic and Wegovy: What Are GLP-1 Weight-Loss Medicines?

Evidence-checked Published 16 July 2026·2 min read
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The short version

Mounjaro, Ozempic and Wegovy are prescription medicines, not lifestyle products, and they are not all the same drug. They copy a gut hormone that curbs appetite, they have produced substantial weight loss in trials, and they need a doctor's supervision to be used safely.

Three names now dominate every feed and family group chat: Mounjaro, Ozempic and Wegovy. They tend to be talked about as one interchangeable "weight-loss injection," which is where the confusion starts. In fact they are prescription medicines with different active ingredients, different approved uses, and real safety considerations. Mounjaro contains tirzepatide, while Ozempic and Wegovy both contain semaglutide, and they work by imitating a gut hormone your body already uses: after you eat, it signals fullness to your brain, so you feel satisfied sooner, eat less, and your blood sugar steadies.

The trial numbers are genuinely strong, though they are averages rather than a promise for any one person. In a large study of adults with obesity but without diabetes, published in the New England Journal of Medicine, semaglutide with lifestyle support produced an average weight loss of 14.9 percent over 68 weeks, and a 2025 head-to-head trial found tirzepatide produced even more. Some people lose far less, and some cannot tolerate the medicines at all, which is why they are only part of the picture.

That picture matters because these are treatments for a health condition, not a cosmetic shortcut. The World Health Organization's 2025 guideline recommends them for adults living with obesity, and only as part of a comprehensive plan that includes healthy eating, activity and professional support. Common side effects such as nausea, vomiting and constipation are usually worst as the dose rises, and the WHO has warned that soaring demand is fuelling fake and substandard products, so how you get the medicine is as important as whether you take it.

What you can do

Important: Whether these medicines suit you is a clinical decision only a qualified doctor can make after assessing your health. This article is information, not a prescription.

Key message

The receipts: peer-reviewed & official sources

Every claim in this article traces back to these 3 sources.

  1. WHO: GLP-1 questions and answers
  2. Semaglutide trial, NEJM
  3. Tirzepatide vs semaglutide trial, NEJM
This article explains evidence. It does not diagnose, prescribe, or replace a consultation with a qualified clinician. A registered doctor reviews articles before final publication.
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