Feeling wiped out or starving after a trip to the gym or a jog in the park? Start by taking a closer look at what you eat and drink before, suggests Kelly Pritchett, Ph.D., R.D., an assistant professor in nutrition and exercise science at Central Washington University in Ellensburg, Wash.

Healthy eating and exercise go hand in hand, and it's important to make the right food choices both before and after. So for healthy eating and exercise, what should you have, and when?

“A lot of people assume they have to eat like Michael Phelps, and for most of us that’s not true,” says Leslie Bonci, R.D., owner of Active Eating Advice, which offers nutritional counseling to professional athletes and regular folks. “But if you’re going to be exercising fairly vigorously for about an hour, and you haven’t eaten for about 4 hours, don’t do it on an empty stomach. And you want a little something post exercise, too.”

Before a Workout

Contrary to what you may have heard, it’s fine to have your breakfast, lunch, or dinner in the hour or two before your workout, though some people find that a large meal can cause digestive upset during physical activity.

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That's why a snack that combines fiber-rich carbs and protein 30 to 60 minutes ahead of a workout is your best bet. Keep it small, between 150 and 200 calories. “There’s no reason for 400 calories of anything before exercise,” Bonci says. She adds that you should think outside the box for pre- or post-workout foods you might not usually consider.

Your snack choice should depend on the kind of exercise you’re planning to do. For strength training, for example, a bit of protein—6 ounces of low-fat Greek yogurt, a 100-calorie package of almonds, or a piece of low-fat string cheese—is sufficient to fuel you through a 30- to 45-minute class or routine.

If cardio activity is on your workout menu, complex carbs are an ideal energy source for healthy eating and exercise. Good options for an hour of brisk walking or cycling include a small box of raisins, which contains about 2 tablespoons; a small banana; or one slice of bread with a very thin spread of peanut butter. “These are small, won’t upset your stomach if you’re jostling it up and down as you do in aerobics, and aren’t calorie hogs either,” Bonci says. If you prefer a protein bar, limit yourself to half—with a max of 150 calories. Save the rest for afterward.

If even these small amounts of food bother your stomach during a workout, consider a pre-exercise liquid snack like a low-fat smoothie (8 ounces at most) or a glass of milk. These are usually easier to digest and leave the stomach faster than solid food.

After a Workout

You may have read that a combination of protein and carbs soon after a workout has special benefits for building muscle and replacing fuel stores inside muscle cells. But for the average exerciser, Pritchett says, “as long as you’re fueling well throughout the day and getting adequate protein throughout the day, the timing of protein intake [for building stronger muscles] is not crucial.” And only athletes who work out twice a day need to focus on protein- and carb-heavy "recovery foods" such as protein shakes.

But it's still smart for recreational exercisers to nibble on an appetizer-sized snack within an hour after a workout session. “It helps curb your appetite so you’re not ravenous a couple of hours later,” Bonci says. Such snacks also start a recovery process—the replenishing of carbohydrate (glycogen) stores and rebuilding muscle that can break down during most kinds of exercise. (The exception is strength training, which builds muscle.)

For healthy eating and exercise, a small amount of protein, like a tablespoon of nut butter spread on apple slices, makes a good after-exercise nosh. The apple’s fiber helps to fill you up and nut butters provide satiating proteins and healthy fats. Another good option: a 10-ounce bottle of low-fat milk will help satisfy hunger and quench thirst. And if you prefer something plant-based, try a 100-calorie container of hummus with a few whole-grain crackers.

If you're trying to cut calories and you're a lunchtime exerciser, you can also eat half of your midday meal before you hit the gym and save the rest for afterward. This way, you're not adding any additional calories to your day.

Don't Forget to Hydrate

Also part of your challenge is making sure you get enough liquids. Everyone loses some fluids during a workout, though the amount depends on the temperature, humidity, intensity of exercise, and individual physiology. Some of us simply sweat more than others.

The American College of Sports Medicine recommends drinking 16 to 20 ounces of water or a sports drink at least 4 hours before working out, and another 8 to 12 ounces 10 or 15 minutes after. It also suggests sipping 3 to 8 ounces of water every 15 minutes during an exercise session that's less than 60 minutes, and using a sports drink if you're working out for a longer period of time. 

One way to calculate your post-activity needs, says Bonci, is to weigh yourself right before and right after a workout. The general rule of thumb is that you need 20 to 24 ounces of nonalcoholic liquid for every pound you lose during exercise. “But that doesn’t mean right away—it’s over the rest of the day,” she notes. Or, to cover your hydration bases in a simpler way, drink 10 ounces of water after each exercise session. If you’re someone who sweats heavily, opt for twice that.