We’re learning more about what weight-loss drugs do to the body

We know they can suppress appetite, lower blood sugar, and lead to dramatic weight loss. We also know that they come with side effects, which can include nausea, diarrhea, and vomiting. But we are still learning about some of their other effects.

On the one hand, these seemingly miraculous drugs appear to improve health in other ways, helping to protect against heart failure, kidney disease, and potentially even substance-use disorders, neurodegenerative diseases, and cancer.

But on the other, they appear to be harmful to some people. Their use has been linked to serious conditions, pregnancy complications, and even some deaths. This week let’s take a look at what weight-loss drugs can do.

Ozempic, Wegovy, and other similar drugs are known as GLP-1 agonists; they mimic a chemical made in the intestine, GLP-1, that increases insulin and lowers blood levels of glucose. Originally developed to treat diabetes, they are now known to be phenomenal at suppressing appetite. One key trial, published in 2015, found that over the course of around a year, people who took one particular drug lost between around 4.7% and 6% of their body weight, depending on the dose they took.

Newer versions of that drug were shown to have even bigger effects. A 2021 trial of semaglutide—the active ingredient in both Ozempic and Wegovy—found that people who took it for 68 weeks lost around 15% of their body weight—equivalent to around 15 kilograms.

But there appear to be other benefits, too. In 2024, an enormous study that included 17,604 people in 41 countries found that semaglutide appeared to reduce heart failure in people who were overweight or obese and had cardiovascular disease. That same year, the US approved Wegovy to “reduce the risk of cardiovascular death, heart attack, and stroke in [overweight] adults with cardiovascular disease.” This year, Ozempic was approved to reduce the risk of kidney disease.

And it doesn’t end there. The many users of GLP-1 agonists have been reporting some unexpected positive side effects. Not only are they less interested in food, but they are less interested in alcohol, tobacco, opioids, and other addictive substances.