“You don’t have to adhere to a rigid schedule and there are no hard-fast rules,” said Riska Platt, M.S., R.D., a nutrition consultant for the Cardiac Rehabilitation Center at Mount Sinai Medical Center in New York. “But there are some things you should do before, during and after you work out.”

Here is what Ms. Platt recommends:

Before: Fuel Up!

Not fueling up before you work out is like “driving a car on empty,” said Platt, an American Heart Association volunteer. You also won’t have enough energy to maximize your workout and you limit your ability to burn calories. 

Ideally, fuel up two hours before you exercise by:

• Hydrating with water.
• Eating healthy carbohydrates such as whole-grain cereals (with low-fat or skim milk), whole-wheat toast, low-fat or fat-free yogurt, whole grain pasta, brown rice, fruits and vegetables.
• Avoiding saturated fats and even a lot of healthy protein — because these types of fuels digest slower in your stomach and take away oxygen and energy-delivering blood from your muscles. 

If you only have 5-10 minutes before you exercise, eat a piece of fruit such as an apple or banana.

“The key is to consume easily digested carbohydrates, so you don’t feel sluggish,” Platt said.

During: Make a Pit Stop.

Whether you’re a professional athlete who trains for several hours or you have a low to moderate routine, keep your body hydrated with small, frequent sips of water.

Platt notes that you don’t need to eat during a workout that’s an hour or less. But, for longer, high intensity vigorous workouts, she recommends eating 50-100 calories every half hour of carbohydrates such as low-fat yogurt, raisins, or banana.

After: Refuel Your Tank.

After your workout, Ms. Platt recommends refueling with:

• Fluids. Drink water, of course. Blend your water with 100% juice such as orange juice which provides fluids, carbohydrates.
• Carbohydrates. You burn a lot of carbohydrates — the main fuel for your muscles — when you exercise. In the 20-60 minutes after your workout, your muscles can store carbohydrates and protein as energy and help in recovery.
• Protein. Eat things with protein to help repair and grow your muscles. It’s important to realize that these are general guidelines. We have different digestive systems and “a lot depends on what kind of workout you’re doing,” Platt said.
  So do what works best for you. Know that what you put in your body (nutrition) is as important as you what you do with your body (exercise). Both are crucial to keeping your engine performing at its best.