How Many Calories Do You Need?

Monica Reinagel, MS, LD/N, CNS
2-minute read

Q. I am training for my third marathon and need to pay close attention to my nutrition, but I am confused about the calorie intake needed to maintain a healthy weight during training.  How can I figure out how many calories I should be eating during my training?

A.  Running burns a lot of calories.  Running 10 or 20 miles at a time really burns a lot of calories.  Unless you increase your calorie intake to compensate, you'll probably start losing weight.

Estimating Your Calorie Needs

Whether you're an athlete or a couch potato--and whether your goal is to gain, lose, or maintain--in order to know how much you should be eating, you have to figure out how much you're  burning.  There are lots of calculators that will estimate (more on that in a moment) how many calories you burn on a typical day, based on your size, age, and activity level. Here's one.

As a hypothetical example, let's say you're a 30-year-old woman who is 5'4" and weighs 120 pounds. On a typical day, you burn around 1600 calories--before you do any training.   Add a three-hour training run (18 miles at 6 miles per hour) and you burn an additional 1600 calories.  You can plug in other variables for a ball park idea of what your calorie needs are on training and rest days.

But these are only estimates.  Your results may vary.

A lot.

Here's a fail-proof way to tell whether you're eating enough to replace the calories you're burning.  No calculators required. Hop on the scale once or twice a week.   If your weight starts to trend downward, you're not eating enough.  If you're gaining weight, you're eating too much!

See Also:

What to Eat Before, During, and After a Workout (Nutrition pa)
What to Eat Before and After Exercise (Get Fit Guy)
How to Recover After a Workout (Get Fit Guy)

P.S.  You don't necessarily have to replace  calories on the same day you burn them!  For example, if you burn 1600 on a rest day and 3200 calories the following day,  you could eat 2400 calories each day.You can even tote up your calories for an entire week, based on your training schedule, and pide them or less evenly throughout the week.

Woman Eating Waffles image courtesy of Shutterstock

About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.