Why some runners end up gaining weight

Weight loss isn’t the only goal to aim for.
Weight loss isn’t the only goal to aim for.
Image: AP Photo/John Minchillo
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We’ve all heard it before: weight loss occurs when we eat fewer calories than we burn.

So you would think that running, which burns about 100 calories per mile, would be a great way to lose weight. But sometimes, runners who are training for longer races end up crossing the finish line heavier than when they started training—and not just because of increased muscle mass.

Why, cruel world?

People often assume that because they are running more, they can eat whatever they want. If only.

“Many people equate marathon training to huge volumes of exercise, but in reality, many training programs are not a lot more rigorous than a person’s usual exercise routine,” Mary Kennedy, a nutritionist and marathon training coach based outside of Boston, told the Boston Globe.

Although this isn’t true for all runners, it’s fairly common among amateurs, especially if they’re newer to long-distance running. Running is a high-impact sport on bones and joints; in order to avoid injury, training programs typically increase mileage no more than 10% a week. (For example, if you started out running 20 miles per week, the most you would increase your mileage is to 22 miles the following week.)

It all comes down to how you replace the calories you burn while training—and avoiding overeating and eating the wrong foods. As you start racking up your weekly milage, naturally you’ll feel hungrier. But it’s important that you give your body the nutrients it needs, as opposed to just energy. As we run, we burn calories, but we also use up a lot of resources such as iron, potassium, proteins, and other vitamins. In order to keep adding mileage efficiently, it’s important to replace all of those nutrients.

“Nutrients make your body go, not calories,” writes Laura Ingalls, a health consultant and personal trainer based outside of Boston. “If you’re eating just to replace calories and not taking care to get protein, vitamins and minerals, you may find yourself in a bad place rather quickly… Your body stops being efficient. It slows down. It packs on weight.”

It’s tempting to reach for baked goods, milk shakes, and other foods with lots of fats and simple sugars to quickly replace calories lost to long runs, but those foods won’t replenish your vitamin stores in a way that allows you to maintain your training schedule. Plus, they are calorie-dense and very tasty, so it’s easy to eat more than you burned.

Additionally, recovering and resting are just as important as training is for building up your running. For the overambitious among us, it can be easy to forget this. But when you fail to get adequate sleep or take days off from running, you risk throwing your hormones off balance, which can make you feel more hungry and less full when you do eat. Even if you’re burning a lot of calories through training, hormones can trick you into thinking you need more energy than you actually do, making it easy to overeat.

For this reason, it’s just as important to watch what you eat while training as when you’re in the off-season. As your appetite increases, treat yourself to more sweet potatoes, lean meats, nuts, and leafy greens—all things that pack a punch with vitamins and minerals, and aren’t as calorie-dense as other foods. You can eat a lot and feel satisfied, but still avoid over-consuming calories.

And remember: Gaining some weight doesn’t make reaching your distance goal—whether it’s running six or 26 miles—any less valid. That’s still an accomplishment to feel proud of. If you focus on replenishing yourself with foods higher in nutritional value, you should be able to get back to your target weight while continuing to run the same distances. And, you’ll likely feel stronger, too.

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