Wegovy does not work like a stimulant, like a fat blocker, or like insulin. It works by mimicking a hormone your gut already makes. Understanding the mechanism helps make sense of both the effects and the side effects.

The Hormone: GLP-1

When you eat, your gut releases a set of signalling hormones called incretins. The most well studied is GLP-1, short for glucagon-like peptide-1. It is released by special cells in the small intestine in response to food, particularly carbohydrates and fats.

GLP-1 has several jobs:

  • Tells the pancreas to release insulin (only when blood glucose is up)
  • Tells the pancreas to release less glucagon (a hormone that raises blood sugar)
  • Slows down the stomach so food sits there longer, releasing slowly into the small intestine
  • Acts on the brain (specifically the hypothalamus) to reduce appetite
  • May have effects on the brain's reward centres, reducing food cravings

In people with obesity or type 2 diabetes, the response to GLP-1 is often blunted. The signal is there but the body does not act on it as strongly. Semaglutide essentially turns the volume back up.

What Semaglutide Does

Semaglutide is a synthetic molecule built to look like GLP-1 to the body's receptors. It binds to the GLP-1 receptor and triggers the same chain of effects. Because of its design, it sticks around far longer than natural GLP-1, which is broken down within minutes. Semaglutide's half life is roughly seven days, which is what makes weekly dosing possible.

Practical effects most people notice:

Reduced appetite

This is the effect most people notice first. The medication acts on the appetite centres in the brain, reducing the urge to eat and shortening the duration of cravings. People often describe it as 'food noise going quiet' or just being less interested in food.

Increased satiety

You feel full sooner and stay full longer after a meal. Combined with the slowed gastric emptying, portion sizes naturally drop without conscious effort.

Reduced cravings

Many people report changes in what they want to eat. Highly palatable food (sugary, salty, fatty) often becomes less appealing. This is thought to involve GLP-1's effect on brain reward circuits, though the mechanism is still being studied.

Improved blood sugar control

Insulin is released in a more matched way when food arrives, and the post meal glucose spike is blunted. This is the original use of semaglutide (Ozempic) for type 2 diabetes.

Cardiovascular benefit

Beyond weight loss, the SELECT trial showed semaglutide reduces the risk of heart attack, stroke, and cardiovascular death in people with established cardiovascular disease and excess weight. The mechanism is multifactorial: weight loss, blood pressure reduction, improved blood sugar, and possibly direct effects on blood vessels and inflammation. More on this.

Talk To A Doctor About Whether It Fits You

An online consultation reviews your medical history and decides whether Wegovy is appropriate, and what dose to start at.

Start Consultation

Why It Takes Time

Wegovy starts at 0.25 mg weekly, well below the therapeutic dose, and steps up over four months. The slow titration is because of the gut effects. Your stomach is being asked to empty more slowly than it is used to. That feels uncomfortable in the early weeks, often as nausea, and the body needs time to adapt.

The titration also lets you find your tolerated dose. Not everyone needs to reach the full 2.4 mg. Many people respond well at 1 mg or 1.7 mg and stay there.

What The Medication Cannot Do

  • It cannot replace food choices. Most appetite reduction is mathematical, eating less. The medication makes eating less easier. It does not make poor food choices healthy.
  • It cannot replace movement. Muscle is at risk during weight loss. Resistance training and protein intake during treatment matter. More on this.
  • It cannot fix the cause of obesity if there are specific drivers (medication side effects, untreated sleep apnoea, hormonal conditions). A consultation looks for these.

How Long It Lasts In The Body

Semaglutide's half life is around seven days. After injection, the level peaks at around 24 to 72 hours and stays elevated for the rest of the week. By the next injection, much of the previous dose is still active. This is why missing one dose is not catastrophic.

It also means that stopping the medication is gradual rather than sudden. Levels decline over five to seven weeks after the last dose, with appetite signalling returning toward baseline over that period.

Why Different People Respond Differently

Individual response to semaglutide varies more than you might expect. Some people see strong appetite reduction immediately. Others take weeks. Some respond well at lower doses, others need the full 2.4 mg. A minority of people respond poorly even at maximum dose.

Reasons for variation include genetics (some GLP-1 receptor variants respond differently), starting metabolic profile, what other medications you take, and habit patterns around eating. There is no reliable way to predict in advance how strongly any given person will respond. Treatment is partly trial and adjustment.

Related Reading

Frequently Asked

Not directly. It reduces appetite and slows gastric emptying so you eat less. The energy deficit then leads to fat loss. There are also small effects on how the body uses glucose and fat that contribute.

The body needs time to adapt to the slowed gastric emptying and altered hormone signalling. Starting at 0.25 mg and titrating up gives the gut time to adjust and reduces nausea.

Indirectly. By reducing food intake and improving glucose handling, the medication shifts how the body uses energy. There is no evidence it directly increases metabolic rate like a stimulant would.

Semaglutide has a half life of about seven days. After your last injection, levels gradually drop over five to seven weeks before the medication is essentially cleared.