When healthy young adults eat a low-carbohydrate diet that is higher in protein instead of higher in fat, their blood glucose levels after eating are lower two hours later.

When healthy young adults eat a low-carbohydrate diet high in protein for seven days, their blood insulin levels rise more after a meal than when they eat a low-carbohydrate diet high in fat.

In adults with type 2 diabetes, eating a diet with less carbohydrate and more protein for six weeks leads to lower blood glucose levels after meals and throughout the day, even without losing weight.

For overweight people with type 2 diabetes, eating fewer carbs and more protein for 6 weeks makes it more likely their blood sugar will dip low without them feeling it—82% had low readings compared to 70% on a normal diet—but no one passed out or had a medical emergency.

If you're overweight and have type 2 diabetes, eating fewer carbs and more protein for 6 weeks can slightly lower your blood sugar better than the usual diabetes diet—even if you lose the same amount of weight—because your blood sugar stays more stable throughout the day.

If you're overweight and eat a lot of protein—especially from whey—for a month, your blood sugar might go up a bit, but only if you're also eating very little saturated fat. If you eat more saturated fat, that same high-protein diet doesn't seem to affect your blood sugar.