A Marathon’s Biggest Surprise

Why prepping for a race gives you a 'weighty' shock

Running a marathon changes your life. That’s the conventional wisdom.

There’s a greater sense of self as you push your body to limits you didn’t think possible. You gain increased focus, a greater sense of empowerment.

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Unfortunately, training for a 26.2-mile mega run may also increase something else in your life. 

When Kathryn Dashiell of Ashburn, Virgina, began casually running in 2009, she had one goal in mind — drop the dreaded pounds from her first pregnancy. But when she upped the ante on her morning miles to train for the 2014 Richmond Marathon, she ran into quite the opposite result.

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“During training for my first marathon, like a first pregnancy, I ate whatever I wanted,” the 42-year-old told LifeZette. “I counted calories, but justified my extra consumption by the fact that I was running so much.”

With her extra miles came increased hunger, and with that, increased weight. “I had gained seven pounds by marathon day.”

“It’s common to see an increase of five to seven pounds when beginning to train for a marathon.”

She recently completed her second marathon — and the weight is back.

“I’ve tried cutting calories, but then my running suffers,” she admits. “I wish I could be five pounds lighter, but I’m not sure how attainable that is.”

“Gaining weight while training for a marathon seems counterintuitive, but it does happen,” said chiropractor Scott Schreiber of Newark, Delaware, admitting he experienced this during his own training for the Rock ‘n’ Roll Philadelphia Half Marathon.

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“I was running 20 to 25 miles a week. I was getting skinner, but gaining weight, about 10 pounds,” he said. “I checked my body fat, and I had put on a considerable amount of fat and lost some muscle mass. At first I was surprised, but due to my nutrition background I quickly realized what had happened.”

Schreiber fell prey to what a lot of first-time runners do — poor math skills.

Consider it a simple case of input vs. output. Eat too many calories that are not burned off, you’ll pack on the pounds. Yes, even when running a dozen miles a day.

“When you start to train, the demand for calories and the need to constantly refuel goes up. As training continues, the body’s metabolism changes and becomes acclimated to the regimen,” Schreiber said.

Your body’s new state of hypermetabolism, or being more efficient at turning food into energy, translates to not needing all that extra fuel. But you didn’t get the memo.

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“We think we still need to fuel our body at the same rate. This ‘over-fueling’ leads to weight gain,” he said.

Carson Robertson, who sees plenty of bewildered newbie runners at his Alpha Chiropractic & Physical Therapy in Chandler, Arizona, said there can be a positive side to this gain when it’s the result of increased muscle mass, stored sugars, and extra water intake — all of which can help with the performance to the finish line.

“It’s very common to see an increase of five to seven pounds when beginning to train for a marathon,” Robertson said. “The body has to go through some ‘machinery changes and upgrades’ in response to exercise.”

Robertson is a frequent marathoner who recently ran the 100-mile Javelina Jundred through the Arizona desert.

“Exercise and training increase lean muscle mass. In the early stages, that lean muscle mass increases faster than body fat decreases,” he said.

When the muscle increases but the fat remains the same — your weight goes up.

It’s also the sugar responsible for the pep in your step that can add pounds, Robertson said.

“Training stimulates the body to build more muscle proteins and fibers. Muscles store more glycogen. Those stored sugars cause extra water to be kept in the muscles, further increasing the lean body mass,” he said.

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And don’t discount those much-needed tugs on the water bottle for hydration. All three of these happenings cause larger numbers on the scale and all the panic that goes along with them.

How to Avoid Gaining?
An extra 10 pounds of body weight is estimated to slow your marathon time by about nine minutes, so Robertson urges runners to be reasonable about their training diets. Just because you logged some miles that day doesn’t mean you get an extra doughnut. A 175-pound man burns approximately 130 calories per mile. When he runs 40 miles per week, he’s on average expending 740 extra calories per day during training. If he’s adding 1,000-plus calories, he’ll gain weight.

To maintain your weight during tough training months, Schreiber suggested mixing weight training with running, and avoiding that giant pasta dinner for a “carbo load.”

“In addition, supplement your diet with plant-based protein,” he said. “Protein burns differently than carbohydrates or fat and will be used to spare muscle while training.”

In the end, keep your eyes on the prize, not on the scale.

“Your body will adapt to training,” Schreiber said. “Just give it time to do so.”

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