Hi Sparker--I work out (cardio and weights).. I've always done my workout first thing in the morning--before I eat anything (but AFTER black coffee).. It doesn't bother me at all, on an empty stomach, but I guess there are some who might need to eat first.. Don't know if it's right or wrong--just know that it works for me. I have to get the workout in first thing, or I won't get it done that day..