Something to consider regarding artificial sweeteners: your digestive tract has the same sweet-taste receptors as the taste buds on your tongue. It uses these to decide when to activate sugar metabolizing/storage pathways. Since artificial sweeteners activate the receptors on your tongue, it is reasonable to assume that they also activate the ones in your digestive tract, thus misleading your body about how much sugar it has consumed and causing it to respond inappropriately, probably causing something like a sugar crash as your body releases insulin to combat an influx of sugar that never arrives.
I can only speak for myself, but this is exactly what happens when I consume artificial sweeteners. I get tired, cranky, and hungry about 30 minutes afterwards. I switched from the 'milkshake' style protein drinks after workouts to pure whey isolate and my late night food cravings stopped completely. Too bad the whey isolate tastes, well, awful isn't strong enough of a word.
