If you're asking this question, you're not alone! Many runners, especially those who are training for longer distances, are surprised that their increased mileage doesn't immediately to weight loss despite the fact that they are crushing calories on their training runs. So what gives?
As a health coach who works with quite a few runners, and from my own personal experience as a long distance runner, I've identified the two most likely cause of this phenomenon:
1. Overcompensating by "rewarding" with food
Runners are optimists. They grossly over-estimate the amount of calories they burn and underestimate the calories in the food they consume. I'm not one for counting calories, but we can use the calorie as a piece of date in this simple example:
On Saturday, 130-pound woman runs 10 miles, burning somewhere around 900 calories. She has a carb-rich 350 calorie-breakfast before the run, and during her run, she consumes 250 calories in the form of carbohydrate gels and drinks. Afterward, she rewards herself with a bagel with egg and cheese, about 550 calories. Then she eats a nutritious lunch and dinner--lots of vegetables and lean protein--but she also celebrates her victory with several beers totaling 450 calories, plus a trip to the self-serve frozen yogurt shop, coming in somewhere around 550 calories (it's easy to do once you fill thatcup with a few flavors, top it with cookie dough and brownie bites and add a few candies and a chocolate covered pretzel). At this point, the caloric deficit from that 10-mile run is already been blown.
And the rewards don't stop on Saturday: Sunday morning, our runner acknowledges Saturday's hard work with a pancake breakfast complete with maple syrup and butter.
Our runner would need to seriously cut back on treats and really ramp up the miles over the next few days in order to keep her weight stable or to lose weight if that's her goal, but as additional training runs are conquered, she will "reward" herself all week long.
2. Starting a chain of hunger and binge by not eating the right foods at the right time
Running long distances requires a lot of fuel. Our bodies draw on stores of carbohydrates as well as the carbs that we eat before and during our training runs. At the end of a long run--more than 75 minutes--our bodies need carbohydrates to recover, and will easily store those carbs in our muscles, not as fat.
But some of us, especially my female friends, have gotten the message "Carbs are bad," and instead of nourishing our bodies after a run with a carb-rich snack, we skip it altogether. I understand the rationale that runners try to apply here: "I just ran 10 [or 12 or 18 or 20] miles, and I don't want to blow the caloric deficit I've created by eating."
This thinking is backwards: Right after a tough workout is the one time that you shouldn't skip eating! By skipping the meal or snack after the run, you leave your body under-nourished and unsatisfied, and you're likely to be hit with powerful cravings in the following day or days. Many clients have reported polishing off jars of peanut butter, pounding several granola bars in a row or eating several pieces of buttered bread within a day or two of their long run--and all of them skipped that post-run snack as a habit to try and save calories.
Of course, there can be other factors at play when otherwise healthy runners experience weight gain during training, but I see these two sneaky issues popping up over and over again. The good news is that both causes can be avoided! Plan your meals and snacks carefully, give your body what it needs when it needs it, and consume lots of wholesome foods--vegetables, fruit, raw seeds & nuts, lean protein and whole grains. And of course, if you need support, talk to a professional like me to help get to the bottom of the driving forces that are thwarting your efforts to be your healthiest self!