MS, RD and coach at Brick New York
"You have to be thinking about hydrating throughout the day and not just before or during your workout. Muscles contain a lot of water, and if we don't stay well hydrated they don't function optimally. So instead of being strong and fast, you end up being weak and slow. A lot of pre-workout nutrition is individual, but ideally, about 30 minutes before you work out, you want to have some carbohydrates and protein. Because you don't want the food sitting in your stomach and want the food to be quickly digested, it should be something low in fiber and fat. Fruit and protein powder blended together works well. Egg whites and mashed sweet potato can work too. If you need to have less digestion, 1/2 cup of juice and protein powder might work better. Post workout is the best time to have carbohydrates because your muscles suck those nutrients right up. It's also acceptable to have some fat at this time. Depending on how much you sweat, electrolytes can be more or less important. If you work out like a beast and you sweat like crazy, you need to make sure you get enough sodium and potassium in your diet. I tell my sweaty athletes to salt their food. Great sources of potassium are coconut water, bananas, potatoes, tomatoes and oranges."