"During physical activity, blood is diverted away from the gut and into the working muscles. If you eat a large meal shortly before an intense workout, chances are the food is going to sit undigested in your stomach and cause distress," Natalie explained.
The same can happen if you eat fatty foods before a workout because they take a long time to digest. Natalie suggests choosing easily digestible simple carbs like fruit or starches for pre-workout fuel.