Lean and Hard

It isn't always fun to learn that something you've heard over and over and accepted as true is actually false. On the other hand, it can be liberating. True information is usually helpful, and so we shouldn't be afraid to have our cherished health and fitness beliefs challenged. Here is a commonly held idea that turns out to be untrue:

Thin people are thin because they have a faster metabolism.

You know how it goes. I know how it goes, because I believed it too. I'd look at someone who was thin and wish I had their amazing, bird-like metabolism. They can eat whatever they want and stay thin as a spike. Along the same lines is the idea that you have a fast metabolism when you're young, but it slows down as you age.

The truth is, people who are thinner will have slower metabolisms than people who are heavier. Not faster. Slower. Why is that? Because it takes more energy, more work, hence more calories to move a heavy body around than a lighter body. Try it yourself with any object. That's why heavier vehicles, other things being equal, get worse gas mileage than lighter vehicles do.So how do thin people stay thin? Only three possible explanations exist: They burn more, consume less, or both. Thinner people find physical activity to be more comfortable. Moving around is easier, so they tend to do it more. The opposite happens when we get older and eat more. We gain weight, move around less, gain even more weight, and on and on it goes.

And why do young people get to eat more without gaining weight? Some of the energy they take in, in the form of calories, will go into growth, yes, but they are usually far more active than older folks and pay more attention to their appearance, and so probably eat less, not more, than older people do. When the older ones get married, there's less reason to care about diet and exercise, since they've already satisfied the evolutionary imperative to find a mate and pass on their genes. When we were young there were also probably some restraints put on our eating. When we get to be adults, the only people who can stop us from having that pie are the ones staring back at us in the mirror. The physical demands of our jobs also tend to become less energy-intensive as we age.

But all these reasons have to do with the same factors: Calories in, and calories out.

Is that discouraging? It shouldn't be! Because it means that you are not subject to the immutable dictates of a mysterious entity called your metabolism. You have the power to change, to transform your body using two tools. Diet, and exercise. And that's great news.

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