Ok...ya'll are not getting it. Protein shakes in and of themselves will NOT make you gain weight. If you are taking them in place of another meal, and therefore your calories have remained the same...they will not make you gain anything...you're trading calorie for calorie (and yes, I am aware you may be using a different macronutrient...but let's not even worry about that at the moment). Now if you're taking a shake in ADDITION to your regular meals...I can see adding weight...but this is due to an increase in calories...not because you are drinking a protein shake.