Wegovy works by mimicking a natural gut hormone called GLP-1, which your body releases after eating. The active ingredient, semaglutide, activates the same receptors as this hormone but lasts far longer in your system, creating a sustained feeling of fullness that makes it easier to eat less. People taking Wegovy at its full dose typically lose around 15% of their body weight over about 16 months. The drug affects your brain, your digestive system, and your blood sugar regulation simultaneously, which is why it’s more effective than older weight loss medications that targeted only one pathway.
How It Changes Your Appetite in the Brain
The most powerful effect of Wegovy happens in two parts of the brain that control hunger. In the brainstem, it activates neurons that generate the “I’m full” signal you normally feel after a large meal. At the same time, it quiets a group of neurons in the hypothalamus called AgRP neurons, which are your brain’s hunger alarm system. These neurons normally ramp up when you lose weight, essentially screaming at your brain that you need to eat more. Wegovy suppresses that signal.
This dual action is what makes the drug feel different from willpower alone. When you diet without medication, those AgRP neurons become increasingly active as you lose weight, driving intense cravings and hunger that make regain almost inevitable for many people. Wegovy keeps those neurons quiet even as the scale drops, so the biological pressure to overeat stays muted. Many people describe the experience as food simply occupying less mental space: they stop thinking about their next meal, lose interest in snacking, and feel satisfied with smaller portions.
How It Slows Your Digestion
Wegovy also works in the gut itself. It activates GLP-1 receptors on gastric nerve cells, which slows the rate at which food leaves your stomach. When your stomach empties more slowly, you physically feel full for longer after eating. This effect is most noticeable in the first hour after a meal and is strongest when you first start taking the medication.
Over time, the gastric slowing effect does diminish somewhat, which is one reason the early weeks of treatment often bring the most intense feelings of fullness (and the most digestive side effects). But even as the stomach effect tapers, the brain effects continue working, which is why weight loss typically continues well beyond the first few months.
Effects on Blood Sugar and Metabolism
Wegovy also changes how your body handles blood sugar after meals. It increases insulin release, but only when blood glucose is actually elevated, which prevents the dangerous blood sugar drops that some older diabetes drugs caused. At the same time, it suppresses glucagon, a hormone that tells your liver to release stored sugar into the bloodstream. The net result is more stable blood sugar throughout the day, with fewer of the spikes and crashes that can trigger hunger and cravings.
This metabolic effect is particularly meaningful for people who have insulin resistance or prediabetes, conditions that often go hand in hand with excess weight. More stable blood sugar means less of the cycle where a sugar crash triggers overeating, which triggers another spike, and so on.
Cardiovascular Benefits Beyond Weight Loss
In a large trial called SELECT, semaglutide reduced the risk of major cardiovascular events (heart attack, stroke, and cardiovascular death) in people with obesity and existing heart disease. Among participants with heart failure, the risk dropped by roughly 28%. This benefit appears to go beyond what weight loss alone would explain, suggesting the drug has direct protective effects on blood vessels and inflammation, though the exact mechanisms are still being studied.
Who Can Get a Prescription
The FDA has approved Wegovy for adults with a BMI of 30 or higher, or a BMI of 27 to 29.9 if they also have at least one weight-related health condition such as high blood pressure, type 2 diabetes, or high cholesterol. It’s also approved for adolescents aged 12 and older whose BMI falls at or above the 95th percentile for their age and sex. In all cases, it’s intended to be used alongside a reduced-calorie diet and increased physical activity, not as a standalone fix.
How the Dosing Ramps Up
You don’t start at the full dose. Wegovy uses a gradual five-step schedule over about four months to give your body time to adjust:
- Weeks 1 through 4: 0.25 mg once weekly
- Weeks 5 through 8: 0.5 mg once weekly
- Weeks 9 through 12: 1 mg once weekly
- Weeks 13 through 16: 1.7 mg once weekly
- Week 17 onward: 2.4 mg once weekly (maintenance dose)
Each dose is a once-weekly injection. If a particular step causes too many side effects, your prescriber may hold you at that dose for an extra four weeks before moving up. The slow escalation exists specifically to reduce nausea and other gut symptoms, which tend to be worst during increases.
What Side Effects to Expect
Digestive issues are by far the most common side effects, and most people experience at least some. Nausea, diarrhea, vomiting, constipation, and abdominal pain all occur in more than 5% of users. Other common effects include headache, fatigue, dizziness, bloating, acid reflux, and hair loss. About 4.1% of people in clinical trials experienced severe gastrointestinal symptoms, compared to less than 1% on placebo.
Most of these side effects are worst during the dose escalation period and tend to improve once your body adjusts. That said, nausea was the single most common reason people stopped the medication in trials, though only 1.8% actually discontinued for that reason. For the majority, the side effects were manageable and temporary. Eating smaller meals, avoiding fatty or greasy foods, and staying hydrated can help during the adjustment period.
What Happens if You Stop
Wegovy doesn’t permanently reset your body’s weight set point. The appetite-suppressing effects last only as long as the drug is in your system. When people stop taking it, the hunger signals it was suppressing come back, and most people regain a significant portion of the weight they lost. This is why the FDA indication specifically includes the phrase “maintain weight reduction long term,” signaling that the drug is designed for ongoing use rather than a short course. For people considering Wegovy, it helps to think of it less like an antibiotic you take until you’re better and more like a blood pressure medication you stay on to keep the condition managed.