What Does Wegovy Actually Do Inside Your Body?

How does Wegovy actually signal the brain to eat less?

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases naturally after eating. It travels to receptors in the brain's hypothalamus (the region that governs hunger and satiety) and tells it the meal is done. The signal is real, but short-lived under normal conditions. Semaglutide is a synthetic version of GLP-1 that has been chemically modified so it resists the enzyme that normally breaks natural GLP-1 down within minutes. That modification extends its half-life long enough to sustain the effect across a full week from a single injection.

The practical consequence is a persistent reduction in appetite signals. Many people taking Wegovy describe simply not thinking about food between meals in the way they did before, rather than feeling they are actively fighting hunger. That distinction matters: the medicine changes the underlying signal, not just willpower. The full-body effects of semaglutide cover what this means beyond appetite.

Wegovy also activates GLP-1 receptors in the gut wall itself, slowing gastric emptying, the rate at which the stomach releases food into the small intestine. Meals therefore stretch the stomach for longer, and the post-meal fullness signal persists further into the day. These two pathways (central appetite suppression and peripheral gastric slowing) work together, which is why the weight-loss effect is meaningfully larger than lifestyle changes alone.

What does the trial evidence say about how much weight Wegovy can shift?

The most cited figure comes from the STEP 1 trial: on average, adults taking semaglutide 2.4 mg lost roughly 15% of their starting body weight over 68 weeks, versus about 2.4% for placebo. That is not a ceiling, some participants lost considerably more, others less. Whether Wegovy works explores what drives that variation and what realistic expectations look like.

Semaglutide 2.4 mg is the standard maintenance dose reached through a gradual titration schedule, starting at 0.25 mg and stepping up roughly every four weeks. The titration exists to give the gut time to adjust and to reduce early nausea, the most common side effect reported in trials. The doses Wegovy comes in explains the pen options and what the schedule typically looks like in practice.

The MHRA has since approved a 7.2 mg maintenance dose, following trial data showing around 20.7% average weight loss at that level over 72 weeks. The dedicated single-dose 7.2 mg pen was approved on 14 April 2026, for adults with a BMI of 30 or above. Whether a higher dose is appropriate for any individual is a clinical decision. As with all doses, availability is confirmed at consultation, not assumed.

The cost context for Wegovy in the UK is worth reading separately if you are weighing up the private route.

Does Wegovy stop working after a while, and what happens if you stop taking it?

This is probably the question our prescribers hear most consistently. The short answer: weight loss typically slows and then plateaus as the body reaches a new equilibrium, which is not the same as the medicine failing. Sustained weight management at that lower set point is itself the goal.

Stopping Wegovy is a different matter. Clinical evidence shows that much of the weight lost during treatment returns when the medicine is discontinued (often within a year) if diet and activity habits have not changed substantially in parallel. The evidence on whether Wegovy eventually stops working covers this distinction in detail, including what the data says about long-term use.

This is one reason that prescribers and guidelines from NHS England on weight-management injections emphasise that Wegovy works best alongside meaningful dietary and activity changes, not instead of them. The medicine changes the hormonal environment; building sustainable habits consolidates the result. A pause for a holiday or a month when budgets are tight is worth discussing with your prescriber rather than simply stopping.

Who is Wegovy licensed for, and does BMI tell the whole story?

The UK licence covers adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as hypertension, type 2 diabetes, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance, reflecting different metabolic risk profiles at a given BMI. For an overview of the broader treatment landscape, the weight-loss treatment options page maps out where Wegovy sits.

BMI alone never decides the outcome of a clinical assessment. A prescriber looks at your full medical history, any medicines you already take, and conditions that might affect suitability. Pregnancy, breastfeeding, and actively trying to conceive are situations where Wegovy is not recommended; the same applies to anyone under 18. Certain conditions (including a personal or family history of medullary thyroid carcinoma) require particular care.

NICE's appraisal of semaglutide for weight management, TA875, sets out the criteria under which it is recommended on the NHS via specialist services. Private prescribing follows the licensed indications and the prescriber's clinical judgement rather than NICE's commissioning thresholds.