It is very important to be in a fed state prior to exercise. Eating too much, or having too much sugar or dairy, can make you feel sick. It is extremely important if you work out first thing in the morning in order to have sources of fuel for the workout. Soluble protein and carbohydrates are so important.

That’s one school of thought. They are trying to burn calories. I prefer eating a high GI meal right before to get carbs in my bloodstream with some carbs, fat and protein. Data supports this.

That is old school thinking. It correlated with the not eating before swimming because of the risks of cramping. The more modern theory of exercise is that food before eating is generally helpful. If it is a endurance event, carbohydrates are essential for energy. If it is more of a high intensity training or weight lifting, protein should certainly be part of that preworkout diet.

Should give your food time to digest prior to workout for lots of reasons

At least a small amount, but don't overdo it.

Depends on the type of exercise you are completing. My partner, Dr. Jesse Morse, walks every morning fasted (last meal 8+ hours before), however before strength training a combo of protein + carbohydrates + (small amount of) fat is vital to fuel the workout.

Working out on an empty stomach could cause your blood sugar to drop (i.e., low blood sugar) causing one to be nauseated, lightheaded, or dizzy. I would recommend eating a small portion of protein and carbohydrates 30-45 minutes before a workout and keep hydrated. A large meal should be avoided before a workout. May eat a regular meal 30-60 minutes after your workout.

Mark Burt, M.D.