Immediately Before a Workout
If you haven't eaten in a while, don't skip out on food — even if you're just about to head into the gym, says Heidi. Your body will need the energy to power through whatever vigorous workout you put it through. Restrict this snack to simple carbs (up to 15 grams), and keep it light: seven to nine jellybeans, an eight-ounce sport drink, or one slice of white bread should do the trick. The key is to stick to simple sugars that won't cause digestive discomfort midway through your workout.