For triathletes, foodis fuel. So don't fill your tank with sludge. "Poor training days are often due to poor eating days," says Suzanne Eberle, M.S., R.D., author of Endurance Sports Nutrition.

This plan is designed to give you sustained energy for your workouts, help your body recover from training, and to give you peak performance on race day. You'll notice it's different from the advice you may have read elsewhere in Men's Health, and for good reason: This isn't a fat loss or muscle-building diet. Here, we're talking about performance-specifically, your best performance possible.

What to Eat

Triathletes should break their diets into three phases: off season, peak season, and tapering, says Tim Ziegenfuss, Ph.D., CEO of the Center for Applied Health Sciences. The only real difference between the three stages? Carb intake. "Carbohydrates are the most important fuel." People who are training for a triathlon should be eating 2 to 3 grams of carbs per pound of body weight every day.

Recent studies have also shown that pairing carbohydrates and proteins help your muscles recover from training. "Instead of just a bagel or an apple, have it with some peanut butter or nuts," says Ziegenfuss.

Don't get too excited-this doesn't give you free reign to eat all of the pasta you want. "You still have to match your caloric intake to caloric expenditure, or else you'll gain body fat," Ziegenfuss warns. Also, make sure you're making healthy choices-lots of fruits and veggies, making your carbs whole grains-and drinking lots of water all day.

When to Eat

You want to time your nutrition so that you have fuel for longer workouts. Eat a meal of mostly carbs and a bit of protein 2 to 3 hours before a workout. Ziegenfuss recommends eating your post-workout meal of 4:1 ratio carbs to protein 15 minutes post-workout. This is the time your body is most receptive to refueling levels of the stored energy called glycogen in your muscles. But if you can't meet that window, don't sweat it-just refuel as soon as you can.

Staying Hydrated

"Dehydration as little as 2 percent can impair performance," says Ziegenfuss, so make sure you're consistently hydrated throughout the day. Your urine should be a light yellow color most of the time.

Race Fuel: Gels, Sports Drinks, and Bars

Sports drinks and gels are another way of getting key nutrients during training, but figuring out what's right for you is all about experimenting. Mix and match different drinks and gels to see what works best and gives you the best training sessions. Gels are popular, especially during the race, because of the small packaging, but some people will prefer a fluid. Ziegenfuss suggests trying a carb-protein mixture to help meet your energy needs before or after the race. As long as you're eating your pre-workout meal, you shouldn't need additional race nutrition for workouts shorter than 90 minutes.

The Week of the Race

Carbo-loading the week of the race is a thing of the past. Slightly increase your carb intake (Ziegenfuss suggests 3 grams per pound of body weight) one to two days before the race, and leave the rest of your diet untouched. This will help store more energy in the muscle and keep you fueled for race day.

The Day of the Race

The biggest thing to remember the day of the race is to never try anything new. Testing out a new brand of sports gel or eating something different for breakfast is the quickest route toward an upset stomach, which is the last thing you want mid-triathlon. Eberle cautions, "Think about workouts and meals as dress rehearsals for race day."