Eating for Endurance


Don’t put energy on the class waitlist

   From Fitness Trainer May/June

When you have a room full of motivated individuals—who woke up early just to make the online cut for your class and are ready to ‘Sweat. It. Out !’ well, you’ll want to make sure they are fueled for the energy output you’re about to demand of them. Here’s what you want to know about eating for endurance, based on the Joint Position Statement on Nutrition for Athletic Performance from the American College of Sports Medicine, the Academy of Nutrition and Dietietics, and Dietitians of Canada.


1. Eat Enough Calories

Most athletes need ~21 calories per pound (45 cal/kg) of lean body mass (LBM). That means, if you weigh 150 pounds and have 10% body fat, your LBM is 135 pounds and you require about 2,800 calories a day.

That said, energy needs vary from person to person, depending on how fidgety you are, how much you sit in front of a computer, how much muscle you have, etc.. Hence, your body is actually your best calorie counter—more accurate than any formula or app!

If a fitness participant eats intuitively—that is, they eat when they feel hunger and stop when they feel content, they are likely eating enough. But if they stop eating just because they think they should, if they are feeling hungry all the time and are losing weight, they want to eat larger portions. Under fueling is a needless way to hurt performance.

If they can’t tell when enough food is enough, suggest they wait 10 to 20 minutes after eating and then, mindfully ask themselves “Does my body need more fuel?” Those who routinely stop eating just because they have finished their packet of oatmeal (or other pre-portioned allotment) can easily be under-fueled. Even dieting fitness enthusiasts want to surround their workouts with fuel. Their plan should be to eat enough during the day to fuel-up and refuel from workouts, and then eat just a little bit less at the end of the day, to lose weight when they are sleeping.

2. Eat Enough Carbohydrates

According to the Position Statement on Nutrition for Athletic Performance, the optimal amount of carbohydrate on a day with one hour of training is 5 to 7 grams carb/kg. On high volume days, you need about 6 to 12 g carb/kg body weight. For a 150-pound (68 kg) athlete, this comes to about 350 to 800 grams carb a day—the equivalent of about

one to two (1-lb) boxes of uncooked pasta (1,400 to 3,200 calories). That’s more than many of today’s (carb-phobic) athletes consume. You want to make grains the foundation of each meal: choose more oatmeal for breakfast; more sandwiches at lunch; and more rice at dinner to get three times more calories from carbs than from protein. Otherwise, you set the stage for needless fatigue. 

3. Eat Adequate—

but not Excess—


Protein needs for athletes range from 1.4 g/kg (for mature athletes) to 2.0 g protein/kg (for athletes building muscle or dieting to lose fat). For a 150-pound (68 kg) athlete, protein needs come to about 95 to 135 grams protein per day, or 25 to 35 grams protein four times a day. That means 3 eggs at breakfast (with the bowl of oatmeal), a hearty sandwich at lunch, portion of lean meat/fish/chicken at dinner, and cottage cheese (with fruit) for an afternoon or bedtime snack.

For vegetarians, generous servings of beans, hummus, nuts and tofu at every meal can do the job; a light sprinkling of beans on a lunchtime salad will not. By consuming protein every 3 to 5 hours, you will optimize muscle building and deter muscle breakdown.

4. Fill in the Calorie-gap With Fat

Include in each meal and snack some health-promoting, anti-inflammatory fat: nuts, salmon, peanut butter, avocado, olive oil, etc.. Fat adds flavor, offers satiety, and is a source of fuel for endurance exercise. Training your muscles to burn more fat for fuel happens when you do long, steady “fat burning” exercise. By burning more fat, you burn less of the limited carbohydrate (muscle glycogen, blood glucose) stores.

5. Drink Enough Fluids

A simple way to determine if you are drinking enough fluid is to monitor your urine. You should be voiding dilute, light colored urine every 2 to 4 hours. (Exception: athletes who take vitamin supplements tend to have dark colored urine.) Clients and fitness participants will want to learn their sweat rate, so they can strategize how to prevent dehydration. They can weigh themselves nude before and after one hour of intense-pace exercise, during which they drink nothing.

A one-pound drop pre- to post-exercise equates to 16 ounces of sweat loss. Losing two pounds of sweat in an hour equates to 32 ounces (1 quart). To prevent that loss, they should target drinking 8 ounces of water or sports drink every 15 minutes. Participants who pre-plan their fluid intake tend to hydrate better than those who “wing it.”

6. Consume Enough Calories During Extended Exercise

If the participant will be exercising for longer than 60 to 90 minutes, they want to target 40 to 80 calories (10 to 20 g) of carbohydrate every 20 minutes (120 to 240 calories per hour), starting after the first hour (which gets fueled by your pre-exercise food).


The Bottom Line:

If a client is going to train, they might as well get the most out of their workouts. Performance improves with a good fueling plan!

Nancy Clark

Sports nutritionist Nancy Clark MS RD CSSD has a private practice in the Boston-area (Newton; 617-795-1875), where she helps both fitness exercisers and competitive athletes create winning food plans. Her best-selling Sports Nutrition Guidebook, and food guides for marathoners, cyclists and soccer are available at

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