I don't know why you would have heard that. All I can say is I've suggested it for about every possible use a person can think of and with a few exceptions (like I said, not for everyone), it's done the job very well. I use it post-workout. Then I eat like an hour after that a full meal. I train at least 3 hours per day usually and work, bye the time I get to work I'm almost never tired from my workout earlier in the day. Clients of mine use it any time, first thing upon waking, post workout, some use it pre or even during (I don't know how they can drink a shake during though, I'd hork), and last thing before bed.