As more doctors and patients turn to the latest weight-loss drugs, researchers are trying to figure out which drug is right for which patient—and at what point in their weight-loss journey.Key to making those decisions is how effective the drugs are and which side effects people might experience while taking them.

The first head-to-head trial of two blockbuster weight-loss drugs has shown Mounjaro is more effective than rival Wegovy. Both drugs led to substantial weight loss, but Mounjaro's 20% weight reduction, after 72 weeks of treatment, exceeded the 14% from Wegovy, according to the trial's findings.

A new study shows that people Zepbound lost about 50% more weight than those using Wegovy. It was the first head-to-head trial of the blockbuster weight-loss medications.