When scientists block a fat-burning enzyme called ATGL with a drug in mice, their hearts don’t get fatty or stop working—unlike when the enzyme is missing from birth, which causes serious heart problems.

A chemical called Atglistatin works really well to block a fat-burning enzyme in mice—by 95%—but it barely does anything to the same enzyme in humans, so it probably won’t work as a weight-loss drug for people.

Giving a special drug to overweight mice on a fatty diet lowers their insulin levels by 71% and helps their bodies use insulin better—without making them lose weight.

When mice eat a lot of fat and are given a special drug that blocks a fat-breaking enzyme, their livers get less inflamed and scarred—like turning down the volume on liver damage.

When scientists blocked a fat-burning enzyme in overweight mice, their belly fat dropped by three-quarters, fat in their blood fell nearly half, and their livers stored way less fat—suggesting that slowing down fat breakdown might help prevent fat from building up in the wrong places and make metabolism healthier.