Saying that "food X makes you fat" or "fat makes you fat" neglects far too many variables to be worth much. You could eat a Big Mac every day, with an otherwise decent diet and good training, you'd be able to make pretty lean gains. There are plenty of people who've made good gains with Muscle Milk and love the taste. But that doesn't mean there aren't healthier and cheaper choices. If you want saturated fat, go with coconut oil or red meat. Basically, if you use Muscle Milk for a meal or two, it obviously won't kill you, but there are better ways to get those calories.