I've been buying Optimum Gold in 10# bags for many years, but that Impact Whey Isolate recced by labdoor looks very good, too. A very important quality, and an individual one, is palatability. To keep the calories down, it actually has to taste good mixed in plain water. My practice is to have 15g whey in ~6 oz. water 1/2 hour before meals. That's only 60 calories and it knocks the appetite back quite a bit. "Spoils your dinner," as my mother would have put it. I'll also usually have some whey in water in a recovery drink after a ride workout, with varying amounts of sugars, depending on the ride or workout, meals, and when the next workout is.