When the pancreas gets fatty, especially in people whose blood sugar is already high, it doesn’t make enough insulin — like a factory that’s clogged with grease and can’t produce its product properly.

After eating mostly fat for three days, the pancreas of healthy young men released less insulin right after they drank sugar water, even though their blood sugar went higher.

When male rats eat a lot of sugar and fat, their bodies produce less of certain proteins that help control insulin and blood sugar, which might make it harder for them to manage energy properly.