"I only exercise so I can eat whatever I want without gaining weight."
You've probably heard someone say this — it might have even been you who said it — but new research has confirmed that, unfortunately, you can't out-exercise a bad diet.
A study of 300 American men and women concluded that our bodies, which are always working to be more efficient at spending energy, don't burn more calories the more we work out. Instead, they adapt to the higher activity levels to hold onto as many calories as possible.
"The most physically active people [in the study] expended the same amount of calories each day as people who were only moderately active," said Herman Pontzer, an associate professor of anthropology at City University of New York, in a statement.
Pontzer was inspired to study the link between activity and energy expenditure after working among the Hadza, a population of traditional hunter-gatherers in northern Tanzania.
Though the Hadza are incredibly active and perform lots of physical labour every day, their daily energy expenditure is similar to people living more sedentary, modernised lifestyles in the United States and Europe.
"That was a real surprise," Pontzer said.
Pontzer said his work shows that those trying to manage their weight or reverse unhealthy weight gain need to focus on their diets to do so.
He added his finding is no excuse to give up your gym membership and loaf on the couch.
"Exercise is really important for your health," Pontzer said. "There is tons of evidence that exercise is important for keeping our bodies and minds healthy, and this work does nothing to change that message."
That sentiment is shared by Dr Krista Scott-Dixon from Precision Nutrition, a Canadian health service that recently teamed up with Virgin Active to offer nutrition coaching.
"We are meant to move as much as possible, in as many ways as possible," she tells 9Coach. "The more you move, the better your body works. The human body is perhaps the only machine that works best when used lots!"
However, she agrees exercise on its own is typically not enough to create the "energy deficit" that leads to weight loss.
She says the key isn't to focus your lifestyle on either diet or exercise, but diet and exercise, and how they work together.
"Think about your diet as a way to fuel the amazing machine that is your body."
"Diet and exercise are like the heart and lungs. Each one benefits from the other," says Dr Scott-Dixon. "Think about your diet as a way to fuel the amazing machine that is your body. Every food choice you make is an opportunity to repair, replenish, take care of, and add value to your body."
It's also important to for everyone to find the balance of exercise and diet that works best for them.
"Some people get hungrier when they move. Some people get less hungry and may need to remind themselves to eat regularly. Some types of movement can suppress appetite for some people; others can increase appetite for some people.
Also, some people prefer to move with a relatively empty stomach, while others do best when they eat consistently every few hours."
"Learn your own unique body cues, and what makes you feel best."