Wegovy (semaglutide) works by mimicking a natural gut hormone called GLP-1 that regulates appetite, blood sugar, and digestion. It acts on multiple systems at once: reducing hunger signals in the brain, slowing how fast food leaves your stomach, and improving how your body handles insulin. In clinical trials, people taking Wegovy for 68 weeks lost significantly more weight than those on placebo, and the drug is now also approved to reduce cardiovascular risk.
How It Reduces Hunger in the Brain
After you eat, your gut naturally releases GLP-1 (glucagon-like peptide-1), a hormone that tells your brain you’re full. The problem is that natural GLP-1 breaks down within minutes. Semaglutide is a modified version of this hormone, engineered to last much longer in your body. With a half-life of roughly 6.5 days, a single weekly injection keeps levels steady enough to continuously influence appetite.
The drug targets appetite-regulating centers in the brain, particularly areas involved in satiety and food reward. One interesting finding: semaglutide appears to change how the brain’s reward system responds to food. In animal studies, it increased dopamine activity during actual food consumption but did not increase dopamine signaling in response to food cues alone. In practical terms, this means the drug may help you feel more satisfied by what you eat while reducing the pull of cravings triggered by seeing or smelling food. People on Wegovy consistently report feeling less preoccupied with food and fuller after smaller meals.
Slowing Digestion to Keep You Full Longer
Wegovy also slows gastric emptying, the rate at which food moves from your stomach into your small intestine. When food sits in your stomach longer, you feel physically full for a longer stretch after eating. This effect is strongest in the first hour after a meal and most pronounced when you first start the medication. Over several weeks, the degree of gastric slowing tends to diminish somewhat, though it doesn’t disappear entirely.
This slower digestion is part of why Wegovy works so well for weight loss, but it’s also the source of its most common side effects. In one analysis, 24% of patients taking semaglutide had residual food in their stomachs during endoscopy procedures, compared to just 5% of patients not on the drug. If you’re scheduled for surgery or a procedure requiring an empty stomach, your care team will likely want you to stop Wegovy well in advance, sometimes up to three weeks beforehand.
Effects on Blood Sugar and Insulin
Semaglutide was originally developed for type 2 diabetes, and its effects on blood sugar are a core part of how it works. The drug stimulates your pancreas to release more insulin when blood sugar rises after a meal, while simultaneously suppressing glucagon, a hormone that raises blood sugar. This dual action helps keep blood sugar levels more stable throughout the day. Even if you don’t have diabetes, these metabolic improvements contribute to the overall shift in how your body processes and stores energy.
What the Clinical Trials Showed
The landmark STEP 1 trial enrolled nearly 2,000 adults with obesity (BMI of 30 or higher) or overweight (BMI of 27 to 29.9) with at least one weight-related health condition. Participants took Wegovy for 68 weeks, roughly 16 months, alongside a reduced-calorie diet and increased physical activity. The weight loss seen in the semaglutide group was substantially greater than in the placebo group, establishing Wegovy as one of the most effective weight-loss medications available.
Beyond weight, the SELECT trial demonstrated cardiovascular benefits. Among patients with obesity and established heart disease, semaglutide reduced major adverse cardiovascular events (heart attacks, strokes, and cardiovascular death) by roughly 28%. The benefits held for patients with heart failure as well, with reductions in cardiovascular events of about 31 to 35% depending on the type of heart failure.
The Dosing Schedule
Wegovy isn’t started at full strength. You follow a gradual dose escalation over about four months to give your body time to adjust and minimize side effects:
- 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: 1.7 mg or 2.4 mg once weekly (maintenance dose)
Because the drug takes about four to five weeks to reach steady-state levels at each dose, you won’t feel the full effect of a new dose right away. Most people notice appetite changes within the first few weeks, but peak weight loss tends to occur gradually over many months. The injection is given subcutaneously, typically in the abdomen, thigh, or upper arm, and peak absorption occurs about four days after each dose.
Common Side Effects
Gastrointestinal symptoms are by far the most frequent side effects, and they’re a direct consequence of how the drug works. In adult clinical trials, 44% of people on Wegovy experienced nausea compared to 16% on placebo. Diarrhea affected 30% (versus 16% on placebo), and vomiting occurred in 24% (versus 6% on placebo). Rates were similar in adolescents, with vomiting actually higher at 36%.
These side effects are typically worst during the early weeks and during dose increases, which is exactly why the titration schedule exists. Most people find that nausea and other symptoms ease as their body adjusts to each dose level. Eating smaller meals, avoiding high-fat foods, and not lying down immediately after eating can help. For some people, side effects remain bothersome enough that they stay at the 1.7 mg dose rather than moving up to 2.4 mg.
Who Can Take It
Wegovy is FDA-approved for adults with obesity (BMI of 30 or above) and for adults with overweight (BMI of 27 or above) who have at least one weight-related condition such as high blood pressure, type 2 diabetes, or high cholesterol. It’s also approved for adolescents aged 12 and older with obesity. The drug is intended to be used alongside dietary changes and increased physical activity, not as a standalone treatment. It’s a long-term medication: stopping it typically leads to weight regain, as the appetite-suppressing and metabolic effects wear off once the drug clears your system.