Why does this weight-loss drug make your brain light up when you eat sweets — even when you eat less?

In male mice that are food-restricted, a single injection of semaglutide reduces behaviors related to seeking sugary rewards while increasing activity in dopamine-producing brain cells during consumption of those rewards.

Medications that activate GLP-1 receptors are associated with lower urges to eat high-calorie foods and reduced persistent thoughts about food in people.

In male mice that are food-restricted, low doses of semaglutide reduce normal food intake but do not change their motivation to seek sugar or alter dopamine activity in a brain region linked to reward processing.

In male mice that are food-restricted, semaglutide increases activity in brain cells involved in reward when they consume sugar, but not when they encounter a signal that predicts sugar will be coming. This suggests the drug affects how the brain responds to actual consumption, not to the expectation of it.

In male mice on a restricted diet, semaglutide increases dopamine activity when they encounter rewards, whether or not they stop seeking those rewards. This suggests the dopamine change occurs independently of the change in motivation.