They tested how ingesting single meals containing whey, casein (milk protein) and soy protein affected energy expenditure and fat oxidation.
Each test meal contained 459 kcal, with half the calories provided from either whey, casein or soy.
The thermogenic responses from the test meals were compared to a control meal that contained only carbohydrates.
Compared to the carbohydrate meal, all three protein meals resulted in a significantly greater increase in energy expenditure measured for up to five hours later. Whey resulted in a greater increase in thermogenesis over both casein and soy.
Compared to the carbohydrate meal, whey protein resulted in an additional 34 kcal expended over a 5.5 hour period. Fat oxidation was also higher after the whey meal than the other meals.
This study confirms that protein increases energy expenditure more than an equal amount of carbohydrate, and that whey protein provides a higher thermogenic effect than other protein sources.