Peptides/Weight and appetite
Semaglutide
Also sold as Ozempic, Wegovy, Rybelsus
The weekly injection behind Ozempic and Wegovy. It reduces appetite, and in trials people lost around 15% of their body weight.
At a glance
What people use it for
- Losing a significant amount of weight
- Quietening constant thoughts about food
- Managing type 2 diabetes
- Reducing heart attack and stroke risk
How it is taken
A once-weekly injection into the stomach, thigh or upper arm, using a pre-filled pen. A daily tablet version also exists.
Evidence
Strong human evidence
Good to know
- Nausea, vomiting and constipation, especially in the first weeks and after each dose increase
- Muscle loss alongside fat loss if protein intake and strength training are neglected
- Gallbladder problems and, rarely, inflammation of the pancreas
- Weight usually returns after stopping unless habits have genuinely changed
Semaglutide is the most effective weight loss medicine most people will ever be offered, and it is a peptide. It copies a gut hormone called GLP-1 that your body already makes after a meal, the one that tells your brain you have had enough. The natural version lasts about two minutes. Semaglutide lasts about a week.
What it actually feels like
People describe it as the volume being turned down. The constant background negotiation about snacks quietens. Meals finish earlier because you feel full sooner, and the feeling lasts. Nobody has to white-knuckle their way through the afternoon.
That is the honest mechanism. It is not burning fat or speeding up metabolism. It makes eating less feel normal instead of like a fight.
What the evidence shows
This is the rare part of this site where the answer is straightforward. In the STEP trials, adults on the weight loss dose lost roughly 15% of their body weight over 68 weeks, compared to about 2.4% on placebo. In the SELECT trial, people with existing heart disease had around a 20% lower rate of heart attacks, strokes and cardiovascular death. These were large, randomised, placebo-controlled trials in tens of thousands of people.
For diabetes, it lowers blood sugar reliably and has been prescribed for that purpose since 2017.
What to know before
The side effects are mostly digestive and mostly early. Doses start low and increase slowly for exactly that reason, and rushing that schedule is the most common self-inflicted misery.
Muscle is the thing people forget. Rapid weight loss takes muscle along with fat unless you eat enough protein and do some resistance training. That matters more the older you are.
And it is a long-term medicine, not a course. Trials that stopped it saw most of the weight return within a year. That is not a failure of willpower; appetite regulation simply goes back to how it was.
Last reviewed .