Just when you thought it was safe to retrieve the forks and knives you hid during the “Are white potatoes a nutritious natural food or glycemic index hell tuber?” debate, scientists have given us another research study that brings up more questions than it answers.  And this time it’s about your “activitystat”, questioning whether or not humans have an internal set point for activity like it’s commonly thought we do for weight.

Dr. Terence J. Wilkin, a professor of endocrinology at the Peninsula Medical School in Plymouth, England, designed a study to test this out by going to the source of all (hyper)activity in the universe: children. After outfitting the 70 kidlets with accelerometers to measure their activity over the course of four weeks he set them free to run amok as they wished (no word on if ear-tagging was used). The kids were broken down into three groups based on which school they go to – in a sad commentary on the perils of poverty, the private-schoolers had 9.2 hours of P.E. per week, the village-schoolers had 2.2 and the urban-schoolers only got 1.6. The idea was to see how activity levels during the school day affected activity levels outside of school.

The results may surprise you: “When [Dr. Wilkin] collated the data, the weekly activity levels of the students from all three schools were remarkably similar. Students who exercised more at school were less active afterward. In a study published this month in The International Journal of Obesity, Dr. Wilkin and his co-authors conclude that, at least in these 8- to 10-year-olds, ‘activity at one time is met with less activity at another.’” These findings aligned with a similar study performed on adult women in which half of the subjects spontaneously reduced their incidental activity in response to an increase in their workouts. This, of course, has all kinds of ramifications for fitness guidelines.

At first glance these results made intuitive sense to me. Anyone who’s run 20 miles and then come home and begged off going dancing with the girls later that night so they can crash at 8 p.m. in a puddle of their own drool will know what I’m talking about. But the more I thought about this the more it bothered me because while this may be the case for me in isolated incidents when I do something particularly strenuous, it isn’t true for me overall. And because we all know that me and my anecdotal evidence are the most important factor in all scientific research, I have to question Dr. Wilkin and his band of not-so-feisty fifth-graders.

This may shock you: there was a time in my life where I not only did not exercise but I actively avoided it. Really I’m pretty new to this whole fitness scene as I only jumped in – with both feet until I was in over my head and drowning because that’s how I like to do everything – 7 years ago after the birth of my second son. (You can read my how I found fitness story here if you’re curious but be warned that I talk about my sexual assault.) To make a very long story short, I went from being winded carrying the laundry up the stairs to, well, doing what I do now. And over that 7-year span, while I don’t have the accelerometer data to prove it, I greatly increased my activity levels overall. First was because I had to: kids are relentless, if they think you are even considering resting they will immediately get diarrhea or shove a sock down the toilet. Second, though, was because I had so much more energy that I chose to do more.

There is research to support this side as well. Two different twin studies concluded, “While the children’s fidgetiness and enjoyment of activity were dependent on heredity, their actual levels of movement were almost wholly determined by their environment, and in particular by the actions and attitudes of their teachers and parents.” In addition there is the opposite question of what happens to people if you force them to be more sedentary than usual and the research has shown that they usually do not resume their former levels of activity.

My theory, based on minutes of extensive Internet reading and pondering in the bathroom, is that they’re both right. I think that perhaps our bodies do have a set level of activity that makes us feel good and that we gravitate to. But I think that our environment at large can reset our “activitystat” to lower or higher based on what we do. As for the kids in the first study, I’m wondering if the fact they were “forced” to exercise (because it was part of the school curriculum) and so it wasn’t their choice was a factor in choosing whether or not to be active late. Or… maybe not.

What’s your experience – do you have a general level of activity that you gravitate towards? Or do you think that our activity levels are primarily a function of our environment? And just out of curiousity: white potatoes – eat ‘em or avoid ‘em?? (Please don’t throw a fork at me.)

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