Rats on a low-carb, high-fat diet have trouble handling sugar—even if they're not eating extra calories—and their insulin seems to be working fine, which is weird because those two things usually go together.

In rats, eating a high-fat, low-carb diet makes their bodies worse at handling sugar—even when calories are the same or higher—but doesn’t change how sensitive they are to insulin. This suggests the sugar problem might not be caused by insulin issues in these animals.

Eating very low-carb, high-fat food for just three days makes blood sugar spike higher after drinking a sugary drink, compared to eating a normal diet.

After eating a high-fat, low-carb diet for three days, the pancreas releases less insulin right after you drink sugar — even though blood sugar goes up.

When overweight mice eat fewer calories, their blood sugar control gets better — but if their diet is very low in carbs, their blood sugar doesn’t improve as much as if they ate more carbs.

After eating just three days of mostly fatty food instead of carbs, healthy young men had higher blood sugar spikes when they drank a sugary drink, meaning their bodies handled sugar less efficiently.