Engines of Our Ingenuity

No. 1412
NONEXERCISE ACTIVITY THERMOGENESIS:

by John H. Lienhard

Click here for audio of Episode 1412.

Today, we lose weight. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Just back from a delicious lunch at the University Center -- meat loaf, potatoes, and a cookie. I can usually get away with eating like that; my weight stays pretty stable. Now I'm back in my office reading a Science magazine article. As I read, I swing my leg, flex random muscles, rock in my chair. In short, I fidget.

The article is about the role of NonExercise Activity Thermogenesis. The three authors from the Mayo Clinic give that the acronym N-E-A-T, NEAT. They've done an interesting experiment. They found sixteen volunteers whose weight was normal -- both men and women in their twenties and thirties. Then, for eight weeks, they fed them a thousand calories beyond what they needed each day.

During this time they studied three forms of energy expenditure. One was basal metabolism, the normal generation of heat by a body at rest. The second form was postprandial heat generation. That's energy we burn in digesting, absorbing, and storing food. Neither form varied in any consistent way with weight gain.

The third means for burning energy is, of course, exercise. In this case, the doctors carefully monitored conscious exercise and made sure it stayed at a constant low level. But (and here the fun begins) we exercise in two ways: consciously and unconsciously.

So these doctors measured the overall heat generation from physical activity, then subtracted off that part of it which was conscious exercise. What remained was the NonExercise Activity Thermogenesis, or NEAT, for each person.

Some people in the experiment gained almost no weight, and some gained as much as ten pounds. That weight-gain was independent of basal metabolism and postprandial heat generation. But it correlated almost perfectly with NonExercise Activity Thermogenesis. The greater the NEAT, the less the weight gain.

To a born fidgeter, that seems like wonderfully good news. I sit here in my chair noticing my micro-motions for the first time. I catch myself flexing my legs, bouncing my feet heel-to-toe, shifting my position in the chair -- and savoring my excellent lunch of meat loaf with cheese-sautéed potatoes. My body is dealing subconsciously with that meal.

This study is a small one. I suppose it could be subject to statistical noise. Yet it's convincing because the result is so unsurprising. Fancy studies often tell us what we knew was true all along. Did we really need a Surgeon General to tell us that cigarettes are just a legalized drug or that a lifetime in the coal mines gave miners emphysema?

But this study does point to the possibility of behavioral changes. Perhaps there are ways to evoke the processes of subconscious exercise. You may not want to become a fidgeter, but the study does suggest that we can find ways to exercise -- even while we're doing our ubiquitous couch-potato desk jobs.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Levine, J.A., Eberhardt, N.L., and Jensen, M.D., Role of Nonexercise Activity Thermogenesis in Resistance to Fat Gain in Humans. Science, 8 January 1999, pp. 212-214.




Data from the Levine, Eberhardt, and Jensen paper


The Engines of Our Ingenuity is Copyright © 1988-1999 by John H. Lienhard.