If you've been researching weight loss and came across the terms "semaglutide," "Ozempic," or "GLP-1 therapy" — you're not alone. In the last three years, this class of medications has quietly become the most clinically significant advance in metabolic medicine since bariatric surgery. But for most people, the signal is buried under a wall of marketing, social media misinformation, and impenetrable medical jargon. This guide strips that away.
The short answer
Semaglutide is a medication that mimics a hormone your gut naturally produces after you eat. That hormone — glucagon-like peptide-1, or GLP-1 — signals to your brain that you're full, slows digestion, and regulates blood sugar. Semaglutide is a synthetic version of GLP-1 that stays active in your body far longer than the natural hormone, which allows it to produce sustained effects with a once-weekly injection.
The result: most people on clinical doses of semaglutide lose 15–20% of their body weight over 68 weeks — numbers that, until recently, were only achievable through surgery.
Adults treated with 2.4mg semaglutide once weekly lost an average of 14.9% of body weight over 68 weeks — versus 2.4% in the placebo group. 86% of participants achieved clinically meaningful weight loss (>5%).
How it actually works
Here's the mechanism, explained plainly. When you eat, your gut releases GLP-1. This hormone does three key things:
- Signals satiety to the brain. GLP-1 acts on receptors in the hypothalamus — the brain's hunger control centre — telling it you're full. Semaglutide amplifies and extends this signal dramatically.
- Slows gastric emptying. Food moves through your stomach more slowly, keeping you fuller for longer after meals.
- Regulates insulin and glucagon. It prompts the pancreas to release insulin in response to elevated blood sugar, and suppresses glucagon (a hormone that raises blood sugar). This is why GLP-1 drugs were originally developed to treat type 2 diabetes.
The weight loss comes primarily from the first two effects: people on semaglutide simply eat less — not because they're trying to, but because they genuinely don't feel hungry.
Important distinction: GLP-1 medications don't "burn fat" directly or speed up your metabolism. They work by reducing appetite and caloric intake. The weight loss is real and clinically significant — but it requires the medication to remain active. This is why maintenance planning matters from the very beginning.
Semaglutide vs. other GLP-1 drugs
Semaglutide isn't the only GLP-1 receptor agonist. Here's how it compares to the other major players currently available:
Tirzepatide (the active ingredient in Mounjaro) is a newer "dual agonist" — it activates both GLP-1 and GIP receptors simultaneously, producing larger average weight loss than semaglutide alone. At GetGLP, both semaglutide- and tirzepatide-based programs are available, and your doctor will determine which is most clinically appropriate for your health profile.
Who qualifies?
GLP-1 therapy is not a lifestyle product. It's a medical treatment with specific clinical criteria. Standard prescribing guidelines indicate eligibility if you have:
- BMI ≥ 30 (obesity), or
- BMI ≥ 27 with at least one weight-related condition (type 2 diabetes, hypertension, high cholesterol, obstructive sleep apnoea)
Contraindications include a personal or family history of medullary thyroid carcinoma (MTC), multiple endocrine neoplasia type 2 (MEN2), a history of pancreatitis, or certain gastrointestinal conditions. Pregnancy is also a contraindication. A licensed physician must assess each case individually.
Self-prescribing is not safe. GLP-1 medications require a clinical assessment before prescription. Online platforms that dispense these medications without a proper consultation are operating outside safe prescribing norms. Always work with a licensed physician who has reviewed your full health history.
What results should you expect?
Expectations matter — both too low and too high can undermine a program's success. Here's a realistic picture based on clinical trial data and our own patient cohort:
Most patients see measurable weight loss by weeks 4–6, though the first two weeks are typically used for dose titration — starting on a lower dose to minimise side effects. The rate of loss tends to peak between weeks 12–28, with a natural plateau occurring around weeks 52–68.
Common side effects
The most common side effects of GLP-1 therapy are gastrointestinal: nausea, vomiting, diarrhoea, and constipation. These are most pronounced when starting treatment or increasing the dose, and typically improve within 4–6 weeks as your body adjusts. Eating smaller meals, staying hydrated, and avoiding fatty or spicy foods during the titration phase all help significantly.
Serious adverse events are rare but real: acute pancreatitis, gallbladder disease, and (very rarely) kidney injury from dehydration following prolonged vomiting. This is why ongoing medical supervision throughout your program is non-negotiable — not a formality.
A licensed GetGLP doctor can review your health profile and tell you whether GLP-1 therapy is clinically appropriate for you — no obligation, no cost for the consultation.
Key takeaways
check_circle What to remember from this article
- Semaglutide is a GLP-1 receptor agonist — it mimics a natural gut hormone to reduce appetite and regulate blood sugar.
- Average clinical weight loss is 15–22% over 68 weeks, depending on the molecule and dose.
- It requires a prescription and medical supervision — it is not a supplement or over-the-counter product.
- Tirzepatide (dual GLP-1/GIP agonist) produces greater average weight loss and may be appropriate for certain patients.
- Side effects are common early on but manageable with proper dose titration under medical supervision.
- Weight regain after stopping is common without a structured maintenance plan — this is a treatment program, not a one-time prescription.
References
- Wilding, J.P.H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384, 989–1002.
- Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387, 205–216.
- Wadden, T.A., et al. (2021). Effect of Subcutaneous Semaglutide vs Placebo as an Adjunct to Intensive Behavioral Therapy on Body Weight in Adults With Overweight or Obesity. JAMA, 325(14), 1403–1413.