I would recommend using a whey protein shake for a meal replacement. It's much better for you than a slimfast or anything similar to a slimfast shake because those drinks have a lot of sugar in them. I use ON Gold Standard 100% Whey Protein. It only has 1 gram of fat, 30 mg of cholesterol, 60 mg of sodium, 3g of carbs, 1g of sugar and 24g of protein. Oh yeah, 120 calories per serving. Compare it to slimfast. You can mix it with milk or water but I use water. I bought mine from bodybuilding.com (this will not bulk you up). They have a lot of different flavors to chose from also. I was pleasantly surprised by the taste when I used with skim milk for the first time. Now as for water, the taste isn't horrible, but it did take me a few times to adjust to the taste. Eventually I look at it as I'm drinking/eating to fuel my body and look foward to the results I will get from the product than the taste....that's just my two cents though. Hope this helps!