If You’re Not Eating Enough You Might Gain Weight

It's counterintuitive, but when you're training hard, not eating can lead to piling on the pounds.

Heidi Mills

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Shannon Scott thought training for a distance triathlon would help her drop the few extra pounds she’d always hoped to shed.

Scott began working out for an hour and a half to two hours each day. When she didn’t lose weight, she cut back her daily calories to 900 a day. Still, she couldn’t get the scale to budge.

She signed up for Ironman Canada, adding even more volume to her training schedule each week. Aware of the physical demands on her body, she raised her daily caloric intake to 1,200 calories a day, but wouldn’t allow herself to eat any more than that. Each week of training, she gained another pound.

“It was so frustrating and counter intuitive,” Scott said.

Scott is just one of many athletes who start training for an endurance event with the expectation of losing weight. While some do indeed drop weight, others feel defeated as they watch the scale move in the opposite direction. On forums of endurance web sites such as, conversation threads show athletes expressing frustration over weight gain during training.

For Scott and other distance athletes, the pounds come on because they aren’t properly fueling their activities. The body then develops a defense mechanism against the perceived threat of starvation, causing athletes to retain or gain weight.

Dr. Emily Cooper, director and founder of Seattle Performance Medicine, sees Scott and many other patients who are perplexed because they’ve gained weight with endurance training. While some never had a weight problem before, far more have struggled with diets for years.

“It is super common in my practice to see people under-fueling exercise and gaining weight,” Cooper said.

Dr. Rick Kattouf, a trainer, author, and CEO of TeamKattouf Inc., also frequently works with athletes who find themselves gaining weight with endurance training. Many of them decided to prepare for a marathon as a way to lose weight, and fear increasing caloric intake with training volume. When examining their nutrition plans, Kattouf often finds they aren’t eating enough before, during, and after exercise.

“The body goes into preservation mode,” Kattouf said. “It’s very frustrating for the athlete because they feel like they’re training more than they ever have before, and their body composition is going in the opposite direction.”

The scientific process that happens with under-fueled sports activity works like this: A workout session increases ghrelin, a hunger hormone that jacks up the appetite, slows the metabolism, and tells the brain the body is hungry. Athletes can mitigate the production of ghrelin by eating before and during exercise.

At the same time that ghrelin rises, the hormone leptin drops. Leptin reassures the brain that body weight is not too low, so without enough, metabolism drops and the body tries to hold on to fat. Endurance training is known to suppress leptin, especially in women.

The rise in ghrelin and drop in leptin becomes pronounced when athletes don’t take in enough food to support their exercise. Sometimes, they’re consciously restricting calories, as was the case with Scott. At one point, she drank only protein shakes because she wanted to be sure she wasn’t consuming any extra calories.

In other situations, exercising without proper fuel is less intentional. Many busy athletes fit in their workouts in the early mornings, and don’t take the extra time to eat a meal beforehand and immediately after. According to Cooper, even if someone takes in sufficient calories throughout the day, they’ll still face hormonal problems if they fail to eat before and after training.

To avoid falling into this imbalance, Cooper suggests making meals around workouts a priority, and not an option. Since exercise endorphins suppress appetite in some people, anyone training for endurance events can’t rely on hunger alone.

“Athletes need to eat mechanically and not by appetite,” Cooper said.

Kattouf also recommends that his clients adjust their lifestyle to compensate for endurance training. He makes sure they aren’t over-training, balances distance workouts with strength sessions, and advises increases in food and sleep.

Some athletes can alter their nutrition and training plans and see immediate results, while others may need longer to recover. For Scott, the metabolic stress of severely under-fueling and overtraining for so long has forced her to back off all endurance exercise. By resting and eating more, she’s finally begun to lose weight, and her metabolic hormones are beginning to rebound to healthy levels. In the last several months, she’s lost 20 pounds.

Scott isn’t sure if her body will ever let her compete in Ironman distance events again, but for now, she’s happy to feel healthy.

“With or without the weight loss, my energy is amazing and I’m not exhausted,” Scott said. “That is priceless.”

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