When male mice eat soybean oil, even if they don’t gain weight, their blood sugar control gets worse — suggesting that the type of fat in their food might directly mess with how their body handles sugar.

When male mice eat soybean oil, they develop problems with blood sugar and a brain hormone called oxytocin—but it’s not because of two specific chemicals in the oil (linoleic acid or stigmasterol), since even soybean oil with less of those chemicals causes the same problems, and adding those chemicals to coconut oil doesn’t make the problems happen.

When male mice eat soybean oil instead of coconut oil or a low-fat diet, their brain's hunger and metabolism control center changes which genes are active—and all the soybean oil diets look more alike to each other than they do to the other diets.