On its surface, the thinking makes total sense. Cutting calories helps you lose weight; exercise helps you lose weight; one of the best ways to exercise is running. So, if you’re cutting calories and exercising by running, you should be at least twice as effective, right?
In this battle, your enemy is one that is typically an ally: Adaptation. The human body is undoubtedly a miracle, filled with all kinds of ways — some known, others still a mystery — that we naturally defend ourselves by unconsciously making physiological changes to combat threats. One good example is the way our bodies increase blood flow to the skin when it’s cold outside — warming us up by opening blood vessels where needed. One bad example are allergies: conditions caused by the immune system overreacting to harmless substances in the environment that are mistakenly perceived as a threat.
On a similar (if not nearly as frightening as allergies can be) note, when you run long distances, your body adapts to a perceived physical stress. Unfortunately, you can’t explain to your body the difference between running 10 miles a day for training vs. running the same distance because you’re being chased by a T-Rex. So, your body adapts to the repetitive nature of the activity, allowing you to burn fewer calories and hold on to more of them so they can be converted into additional energy if needed.
“If your goal is to be leaner, then greater endurance isn’t really to your benefit,” Lou Schuler, author of the book “The New Rules of Lifting for Women,” tells USA Today.
University of Minnesota physician/former president of the American College of Sports Medicine Dr. William Roberts says that the key is to basically make it so that the randomness of your workout outsmarts your body’s ability to adapt. “If I’m looking at a gym and looking at what can I get the most bang for my buck from, it’s whatever I can use that moves and works the most muscle groups at the same time,” he says, admitting that even though he’s a runner, strength training must be added to the upper body — which long-distance running neglects. “If you can build strength and build muscle mass, you’re going to burn more calories, even if you’re idling.”
According to the 2015-2020 edition of the Dietary Guidelines for Americans, active men should consume up to 3000 calories a day, while women should be around 2400 — of course, such guidelines need to be adjusted for height, activity level and other factors. Those calories are processed through metabolism, and turned into the energy we all need.
“When we talk about calorie burning, we are including calories burned for basal metabolic rate—those calories we need just to maintain our temperature and breathing, etc.—plus the extra calories burned in physical activity,” sports medicine specialist/orthopedic surgeon Natasha Trentacosta, M.D., tells Runner’s World. “The extra activities we do in life burn calories beyond the requirement for basal metabolic rate, and to burn these calories, your body first looks toward readily-available sources, and then subsequently stored energy sources.”
If your calories are in deficit, your body turns to glucose in the liver and muscles. “Eventually, longer duration exercise will deplete the readily available glucose and the glycogens stores, requiring the body to get energy from fat or even muscle protein,” Trentacosta explains. “Your body literally breaks down muscle to provide energy for your run, decreasing your overall lean muscle mass.”
This last resort of the body would typically be used as an adaptation to starvation. But — once again —you can’t have a conversation with your body to explain that you aren’t starving, you’re simply trying to lose weight to fit into that bridesmaid’s dress for your cousin’s wedding. If you trigger starvation mode, your thyroid is likely to suffer — and your body will warn you of this, but rather than a “check engine” light in a car, you’ll just feel really terrible.
The body will also suffer in terms of its ability to recover, and you’ll likely begin to feel the effects of the insufficient vitamin and mineral intake triggered by lack of food — hello, weaker, more breakable bones!
It’s not often that you’re told in modern-day life to ignore common sense and work to overcome your body’s god-given tendency to adapt. For many athletes, the key to achieving the body you want is a smart, varied workout regimen complimented by the fuels necessary to make it happen. Rather than going to extremes, go for a gameplan, and then execute it. Because ultimately, your body’s most powerful muscle is always the brain.