We’ve known for some time that exercise on its own isn’t the complete answer to getting rid of excess weight.
Now research has an explanation — our bodies adapt to more activity so that extra calories are not burned off even with more exercise.
The results of the study, in the journal Current Biology, are a reminder of the importance of combining diet and exercise to get weight loss.
“Exercise is really important for your health,” says Herman Pontzer of City University of New York.
“That’s the first thing I mention to anyone asking about the implications of this work for exercise. 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.
“What our work adds is that we also need to focus on diet, particularly when it comes to managing our weight and preventing or reversing unhealthy weight gain.”
The study fits with previous research showing the benefits of controlling diet. Exercise requires time and consistent effort, and it takes longer to see its results
People who start exercise programs to lose weight often see a decline, or even a reversal, in weight loss after a few months. Large studies have also shown that people with very active lifestyles have similar daily energy expenditure to people in more sedentary populations.
Pontzer says this hit home for him when he was working among the Hadza, hunter-gatherers in northern Tanzania.
“The Hadza are incredibly active, walking long distances each day and doing a lot of hard physical work as part of their everyday life,” Pontzer says.
“Despite these high activity levels, we found that they had similar daily energy expenditures to people living more sedentary, modernised lifestyles in the United States and Europe. That was a real surprise, and it got me thinking about the link between activity and energy expenditure.”
The researchers say there might be a sweet spot for physical activity — too little is unhealthy but too much and the body makes adjustments to adapt.