Most pre workout supplements recommend use on an empty stomach…Why does this matter?
On a full stomach the body cannot fully absorb everything a pre workout has to offer because it’s working on digesting and absorbing from different sources. The more food digesting in your stomach before supplement consumption the less likely you will feel its full effect.
During exercise blood flow increases by 65-75%. In order to meet this demand less blood is distributed to areas that need less oxygen like the stomach, kidney, liver, and intestines . Extra blood is then directed to the skin and muscles that are in immediate demand. The digestion process uses blood that we want focused at our muscles during exercise. Within 5 minutes of eating a meal blood flow is increased by 60%. By splitting up this focus our muscles don’t receive the optimal amount of oxygen and nutrients.
This does not mean you shouldn’t eat anything all day. It is important to maintain a proper diet and eat as needed. To maximize effectiveness of a stimulating supplement reserve a designated window of time for your body to fully digest before working out.
On the extreme end some pre workouts like NO Xplode recommend use 2 hours after a meal. Most pre workouts recommend not eating an hour before consumption. This is all based on estimates of how long it takes for food to be fully digested. Things like protein shakes that absorb quickly don’t require as long of a wait and are ideal.
Meal Size vs Digestion Time
If you are eating a big meal I would recommend doing so 2 hours before. If it’s a light meal anywhere from an hour to 45 minutes will be enough. For the best protein synthesis with fast absorbing whey protein I recommend a protein shake 20 minutes before a pre workout.