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Feeling wiped out or starving after a trip to the gym or a jog in the park?

Take a closer look at what you eat and drink before you exercise, suggests Kelly Pritchett, an assistant professor of nutrition and exercise science at Central Washington University in Ellensburg, Wash.

In fact, healthy eating and effective exercise go hand in hand — and it’s important to make the right food choices both before and after working out.

So what should you have, and when?

Before a workout

Contrary to what you may have heard, it’s fine to have 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.

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,” says Leslie Bonci, a registered dietitian and owner of Active Eating Advice, which offers nutritional counseling to professional athletes and regular folks.

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

If cardio activity is on your workout menu, complex carbs are an ideal energy source. Good options include a small box of raisins, which contains about two tablespoons; a small banana; or one slice of bread with a very thin spread of peanut butter. “These are small and 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 — and save the rest for afterward.

If even these small amounts of food bother your stomach during a workout, consider a liquid pre-exercise snack such as a low-fat smoothie (eight ounces at most) or a glass of milk.

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 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-size snack within an hour after a workout session. Such snacks also start a recovery process. And, says Bonci, “it helps curb your appetite so you’re not ravenous a couple of hours later.”

A small amount of protein, such as a tablespoon of nut butter on apple slices, makes a good after-exercise nosh. Another good option: a 10-ounce bottle of low-fat milk will help satisfy hunger and quench thirst.

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

Part of your challenge is making sure you get enough liquids. Everyone loses some fluids during a workout, after all.

The American College of Sports Medicine recommends drinking 16 to 20 ounces of water or a sports drink at least four hours before working out, and another eight to 12 ounces 10 or 15 minutes after. It also suggests sipping three to eight 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 longer.

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