Once per week for five weeks, researchers had 16 healthy men consume a standardized breakfast (totaling 300 Calories). For lunch, the subjects were given drinks consisting of various amounts of whey protein in random order — 0g (control day), 10g, 20g, 30g or 40g. After 30 minutes, they were offered pizza and asked to eat for 20 more minutes until “comfortably full.” The amount of pizza consumed was measured.
On the control day (0g of whey protein), subjects consumed 1,142 Calories of pizza. The amount of pizza calories consumed was significantly decreased by 153, 159, and 305 Calories when 20g, 30g and 40g of whey protein was consumed before pizza.
Also, the blood glucose response to the pizza meal was significantly reduced by all levels of whey protein, but the greatest effect was seen when 40g of whey protein was ingested before pizza.
These results indicate that consuming whey protein 30 minutes before lunch can suppress appetite and decrease the amount of calories consumed. This effect is associated with less of a spike in blood glucose. Overall, the results point to regular consumption of whey protein to minimize overeating in subsequent meals.