Three hours before lunch, 40 people drank a 330-calorie shake that was high in either protein, fat, or carbohydrates. The participants were no less hungry, and they ate no less (or more) at lunch—or later in the day—after the high-protein shake than after the high-carb or high-fat shake.

What to do

Don’t expect a protein shake to help you feel more full than any shake with equal calories.