Fueling your body the right way before a workout is something to take seriously. You do want to eat something, but not too much. If you fill up before a workout, your digestive system will kick into high gear, stealing blood away from your muscles at just the time when your muscles need blood to perform optimally. To keep this from happening and provide your body with enough fuel to power your workout, you have two options: Eat a full, balanced meal about 2 hours before your workout, or have a small meal (call it a snack) of 150 to 300 calories a half hour to an hour before you hit the weights. That’ll keep your blood sugar stable and provide enough energy for your muscles to work with.

What to eat? Have a mix of protein and easy-to-digest carbohydrates with very little fat. Fruit paired with string cheese or a hard-cooked egg with some grapes are good choices, but my favorite pre-workout fuel options are half of a protein bar; a smoothie made with whey protein powder, water, berries, and flax oil; or low-fat Greek yogurt with agave nectar.

Eating after your workout is important, too; it provides fuel for muscle repair and recovery. You’ll want to have something within 30 minutes of the end of your workout, the time when your body needs to replenish glycogen (muscle fuel) spent during your workout. So, again, have a mix of carbohydrates and protein. The snack should contain about 20 grams of protein, the building block of muscle tissue. That’s why a protein shake is an ideal post-workout mini meal. It’s easy to consume and provides a jolt of protein.

The best post-workout protein shake appears to be one that contains a blend of soy, whey, and casein proteins, according to a study in the Journal of Nutrition. A test panel of exercisers was given either a protein drink containing all three types of powdered protein or a drink made with only whey protein, and then researchers measured how quickly the participants’ bodies broke down the proteins into amino acids used to build new muscle. It turned out that the protein shakes containing soy, whey, and casein generated longer-lasting prote in synthesis, providing a better cocktail for muscle repair and growth.

Finally, be sure to drink plenty of water before, during, and after your workout, but especially before, when most people don’t think to hydrate. So drink 16 to 20 ounces of cool water 2 hours prior to your workout.