Having authored a book on obesity and another more recent book that touches on the high cost of cheap food I read with interest "Beating Obesity," Marc Ambinder's article in this month's issue. The piece, built around his own battle with weight, was enlightening and balanced, but dealt mostly with the supply side of the issue -- the easy availability of palatable food. No question that food plays a critical role, but there's another equally important side to the obesity pandemic that is sometimes obscured in the furor over school lunches, soda, and bake sales: personal computers.
The food system hasn't changed all that much over the past decade as the obesity problem has soared. What has changed is how much and how often most Americans move. The scientific literature linking computer use with obesity and adioposity (fat levels) is enormous...and should be no surprise to anyone who considers how little need most of us have to actually get up from our chairs these days.
Some argue that walking and other low level exertions expend relatively few calories, but this is misleading. To begin, low level exercise -- walking and even standing rather than sitting -- can burn hundreds of extra calories over a day, thousands over a week. Equally important, calorie "burn" is just part of the picture -- exercise also helps modulate hormonal levels that influence eating behavior. Individuals vary, of course, but most of us are not wired biologically to live sedentary lives. And when we do, we are more likely to overshoot -- that is, to overeat relative to our calorie expenditure. This explains why exercise is so critical in preventing weight gain.
In a study published last September, laboratory rats fattened on a high fat diet and then slimmed through calorie reduction maintained their lower weight while eating what they liked if they also ran on a treadmill. Without the treadmill, the rats stayed fat. It seems a regular workout reoriented metabolic pathways, thereby limiting the rats' natural drive to replace the lost body fat. This is the way it works in humans, too, explaining why active people -- like mail delivers and hair stylists -- actually have an easier time maintaining their weight then do those of us who work at a desk all day.
Now that computers have made it possible -- and in some cases even expected -- to sit for hours at a time, it's particularly critical that we encourage activity, at least in our leisure time, and especially for our kids.