Nature's Best Isopure Low-Carb is one of the “leanest” Meal Replacement Powders on the market, with an extremely low carb (3 grams) and fat (1 g) content, but an extremely high protein content (50 grams), along with the vitamins and minerals that all good MRP's include in their formula. The protein is 100% whey protein isolate, which is about as pure and easily-absorbed a protein source as you could want and virtually lactose-free. The problem with many Meal Replacement Powder's is that they're formulated for the broadest market appeal possible, and because of that their formulas are full of compromises; too many carbs for this person, not enough protein for that person, too much fat, etc. They might be fine for everyday users but serious athletes and hardcore trainers have different needs. They'll want substantial amounts of high quality protein plus vitamins and minerals, but very low amounts of carbs and fats. There are many customers like this, but not many MRP's that fit the bill. This may account for the widespread popularity of Isopure Low-Carb among experienced trainers. You can also bet that it's a good product when the best-selling size is a 52-serving 7.5 lb tub! This is not to say that Nature's Best hasn't added anything else to the Isopure. Isopure is enriched with muscle-sparing glutamine, which is a key amino acid for muscle growth and development. Isopure also contains a modest amount of fiber (2 grams) and a very favorable 2:1 ratio of potassium to sodium, which helps to maintain electrolyte balance when you're training hard. So if you want more than your protein powder can deliver, but don't want the middle-of-the-road nutritional profile most MRP's have, then all roads lead to Nature's Best Isopure Low-Carb.