Semaglutide: the science behind GLP-1 weight loss
Semaglutide is the active ingredient behind the prescription medications Ozempic and Wegovy, and it helped define the modern era of weight medicine. In the landmark STEP-1 trial of adults with overweight or obesity, participants on semaglutide lost on average about 15% of their body weight, compared with about 2% on placebo, over 68 weeks. This guide covers what semaglutide is, how it works, what the clinical evidence shows, the side effects to expect, and how a provider prescribes it.
What is semaglutide?
Semaglutide is a once weekly injectable medication in the GLP-1 receptor agonist class. It is FDA approved under the brand names Ozempic (for type 2 diabetes) and Wegovy (for chronic weight management), and as an oral tablet, Rybelsus (for type 2 diabetes).
It works by mimicking GLP-1, a gut hormone your body releases after eating that signals fullness and helps regulate blood sugar. Semaglutide amplifies that signal, which is why appetite and cravings tend to fall.
At Expert Health, semaglutide is prescribed by a US-licensed provider and compounded by an FDA-regulated pharmacy. Compounded medications are not FDA-approved. See the disclaimer below.
How semaglutide works
Semaglutide activates the GLP-1 receptor, one of the body's incretin pathways that govern appetite and how you handle food.
- Quiets appetite, signaling fullness to the brain so you eat less.
- Slows gastric emptying, so food stays in your stomach longer and you feel full for longer.
- Reduces cravings, so the constant "food noise" tends to fade.
- Improves insulin response, which is why the same molecule treats type 2 diabetes.
What the clinical research shows
Semaglutide's weight evidence comes primarily from the STEP trial program. The pivotal trial, STEP-1, was a 68-week study of about 1,960 adults with overweight or obesity (without diabetes), published in The New England Journal of Medicine in 2021.
Participants on semaglutide 2.4 mg lost an average of about 15% of their body weight, compared with about 2% on placebo, and roughly 86% lost at least 5% of their body weight. In a later head-to-head trial (SURMOUNT-5), tirzepatide produced greater average weight loss than semaglutide over 72 weeks (20.2% vs 13.7%).
These results were achieved alongside a reduced-calorie diet and increased activity. Trial averages are not promises, and individual results vary based on dose, adherence, and your biology.
Who it's for, and who it isn't
Semaglutide is a medical treatment, not a lifestyle supplement. A provider confirms it is appropriate before prescribing.
Likely a fit if you…
- Have a meaningful weight goal and want a real medical plan
- Have struggled to lose weight or keep it off with diet and exercise alone
- Want appetite control that is dosed and monitored by a provider
- Are an adult who can complete a quick online consult
Not appropriate if you…
- Have a personal or family history of medullary thyroid carcinoma or MEN 2 (boxed warning)
- Are pregnant, trying to conceive, or breastfeeding
- Have a history of pancreatitis or certain GI conditions (your provider will screen)
- Are looking for an unsupervised source with no medical oversight
Safety and side effects
The most common side effects are gastrointestinal: nausea, diarrhea, constipation, and reduced appetite. They tend to be mild to moderate, peak during dose increases, and ease over the following weeks as your body adjusts. Starting low and titrating slowly, exactly how a provider prescribes it, is the main lever for keeping side effects manageable.
Less common but more serious risks include dehydration from GI effects, gallbladder problems, and pancreatitis. Semaglutide also carries a boxed warning for thyroid C-cell tumors based on rodent studies. This is why provider oversight, screening, and check-ins matter, and why this should never be a gray-market purchase.
How Expert Health prescribes semaglutide
It starts with a free consult. A US-licensed provider reviews your goals and health history and confirms whether semaglutide is appropriate. If it is, you start at a low dose and titrate up over several weeks, the approach shown to minimize side effects.
Your medication is compounded by an FDA-regulated pharmacy and shipped to your door, and provider check-ins every four weeks keep your dose matched to how you respond.
Frequently asked questions
Is semaglutide the same as Ozempic and Wegovy?
Semaglutide or tirzepatide, which is better?
How fast does semaglutide work?
Will I regain the weight if I stop?
How is semaglutide taken?
Sources
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1) · New England Journal of Medicine, 2021
- FDA Approves New Drug Treatment for Chronic Weight Management (Wegovy) · U.S. Food & Drug Administration, 2021
- Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5) · New England Journal of Medicine, 2025
Cost and buying guides
This article is for educational purposes and is not medical advice. Statements have not been evaluated by the FDA, and this treatment is not intended to diagnose, treat, cure, or prevent any disease. Compounded medications are not FDA-approved. Individual results vary. Always consult a licensed provider before starting any treatment.
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