Leaner is better

Your body composition -- or body fat ratio -- should be your main concern, not your weight.
According to the National Institutes for Health, more than a third of American women and nearly a quarter of men are on some kind of weight-loss diet at any given time. Among runners the figure is perhaps a little lower, but probably not by much.

The most popular means of pursuing weight loss are branded diet programs such as the South Beach diet and Weight Watchers. The various popular diets seem quite different on the surface, each claiming its own special reason for being more effective than the others, but beneath the surface they are all essentially the same thing: low-calories diets.

I believe that weight loss is not a worthy goal for most runners to pursue. Nor is dieting (severe calorie restriction) the best way to pursue the proper substitute for the goal of weight loss, which is optimizing body composition. Research has shown that our health is affected not so much by how much we weigh, but rather by how lean we are -- that is, by the ratio of fat-free mass to fat mass in our bodies (commonly measured as body fat percentage).

Men and women who have a high body fat percentage tend to be unhealthy, regardless of whether they're heavy or light. By contrast, individuals who have a low body fat percentage tend to be healthy, again regardless of whether they are heavy or light.

The healthiest men and women have good muscle tone and just enough body fat to perform the functions that body fat is responsible for (e.g. supplying energy).

A lean body composition is also ideal for athletic performance, because muscle is capable of performing work, whereas excess body fat just increases the load the muscles must carry. For these reasons, your weight is not the thing to be concerned about. It's your body composition that's important, with respect to both your overall health and your running.

Optimizing body composition

Optimizing body composition is different from simply losing weight. You can lose weight by losing fat, muscle, water or even bone mass. In order to improve your body composition you must either lose fat, gain muscle or do both. Many athletes feel they would perform better (not to mention look better) if they lost weight. But if you lose muscle (or water) instead of fat, your performance and health will suffer. And the method people most often use to lose weight -- general calorie restriction, or dieting -- is sure to result in some muscle loss, and not necessarily much fat loss.

Severe calorie restriction not only doesn't optimize body composition, but it also compromises running performance by failing to provide adequate energy for workouts and recovery.

Another problem with severe calorie restriction is that it's hard for people to sustain because it causes persistent hunger and requires followers to practice inhuman levels of self-denial of their favorite high-calorie foods. In a Tufts University study that investigated the effectiveness of four popular diets, more than half of the subjects dropped out before the one-year study period was completed.

Feed your muscles, starve your fat

A much better way to optimize your body composition, especially as a runner, is to eat (and exercise) according to the following motto: Feed your muscles, starve your fat.

Feeding your muscles means eating enough calories to preserve your existing muscle tissue and fueling optimal workouts and fast post-workout recovery. It also means working out in ways that ensure most of the calories you eat are used to provide immediate energy or to repair and build muscle tissue. Starving your fat means controlling the amount, types, and timing of the calories you eat to minimize fat storage, and working out in ways that burn off excess fat stores.

There are many simple ways to achieve these effects, which I share in my book, The Cutting-Edge Runner. One example of a way to starve your fat is to trim the waste from your diet. A few key substitutions can easily trim enough calories from your diet to turn a slight caloric surplus into the slight caloric deficit you need to become leaner.

For instance, replace full-fat dairy foods with low-fat alternatives, replace soft drinks and fruit juices with water, and replace that big bowl of ice cream for dessert with a single chocolate candy.

One way to feed your muscles is to strength train. Strength training develops lean muscle tissue, which improves your body composition directly and also indirectly, by increasing your rate of fat burning at rest. Strength training also reduces injuries and enhances running performance. Consuming carbs and protein immediately after your strength workouts will enhance their positive effects on your body composition.

Lean by the numbers

There's a saying among health and fitness experts: "What gets measured gets managed." By measuring your body fat percentage often, you'll naturally make an effort to make that number shrink.

New devices that measure body fat percentage accurately using bioelectrical impedance make monitoring your own body composition as easy as stepping on a scale. Body fat scales made by companies such as Tanita and Omron are available for as little as $40 at pharmacies, department stores and exercise equipment retailers. I recommend taking a body fat measurement at least once every other week.

Get in shape by joining a fitness class near you.

This article was adapted by the author from The Cutting-Edge Runner: How to Use the Latest Science and Technology to Run Longer, Stronger, and Faster (Rodale, $15.95). Click here to purchase a copy.

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