I'm not a nutritionist and there's certainly plenty I don't know, but it's my understanding that whey is one of the more easily utilized proteins for your body. I think the caution should be in that you still need to watch your overall calorie consumption. It's also my understanding that when you consume your protein can also make a difference...though this I would recommend researching further. I have heard of people getting a bit "beefy", but I think this is more in the case of taking whey as an addition to their diet as opposed to as a mini-meal.