Regulating the Appetite for Exercise

Athleisure has taken over popular culture. It seems like everyone is working out. Runners are everywhere we turn. People move through their their days ready for yoga with their mats and togs. And yet, we’re also more sedentary than ever. How can this be? Could it be that our appetite for exercise plays a role? Does more intense exercise time lead to more sedentary time? New research in mice raises some fascinating questions.

More Exercise, Less Routine Movement

Daniel Lark and colleagues used innovative methods to measure the activity of mice – both running on their wheels and wandering around their cages. Mice really seem to love running, and that’s pretty easy to measure. But for their routine movements, the researchers needed infrared sensors to measure every move their mice made. These mice also lived in very special homes: metabolic chambers that measure precisely how much energy they’re burning.

By locking the running wheels, Lark could control a mouse’s running time. And they found that more time running meant less time in routine movement. That’s right. By loafing around off the wheel, these mice came very close to canceling out the extra energy they burned on the wheel.

It’s as if they had a very specific appetite for physical activity. More time on the wheel led to less time moving around the cage.

The Importance of All Physical Activity

Of course, this study was all about mice and running wheels. So for humans, this research does nothing more than raise questions. But we have plenty of human data to tell us that routine movement is important throughout our days.

The brand new scientific report of the Physical Activity Guidelines Advisory Committee puts a spotlight on this fact. For the first time, this report says that replacing sedentary behavior with light physical activity has important benefits for health. That’s not to diminish the value of more intensive exercise. But a pattern that mixes too much loafing with a little working out might not be optimal.

We all have some appetite for physical activity. The challenge will be to find the healthiest ways to satisfy it. Workouts are just one part of the picture.

Click here for the study and here for more from the New York Times. For the report of the Physical Activity Guidelines Committee, click here.

Ready to Run, photograph © frankieleon / flickr

Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.

April 16, 2018