Tuesday, September 25, 2007

Exercise and Weight Loss

New York Magazine has an article titled The Scientist and the Stairmaster (by Gary Taubes) which pokes holes in the belief that exercise effects weight loss. The premise of the article is that exercise has been overhyped as a weight loss tool, and no definitive evidence exists to support the assertion that it does. While this may be true - that exercise alone will not make you lose weight - I think it overlooks other contributions exercise makes to weight loss.

It seems as no one thing will make you lose weight. Just as no one thing will make you happy. A good diet should be the foundation of a weight loss program. The key word there is program. And maintaining weight loss will require maintaining the program. Cut calorie intake, increase the burning of calories, and weight loss will ensue. A study cited by the author finds that...

"...the dozen best-constructed experimental trials that addressed weight maintenance—that is, successful dieters who were trying to keep off the pounds they had shed—they found that everyone regains weight. And depending on the type of trial, exercise would either decrease the rate of that gain (by 3.2 ounces per month) or increase its rate (by 1.8 ounces). As the [study authors] themselves concluded, with characteristic understatement, the relationship between exercise and weight is “more complex” than they might otherwise have imagined."

Not surprising. People are "more complex" than most studies can give them credit for.

It seems that much of the article relies heavily on this statement: "The one thing that might be said about exercise with certainty is that it tends to make us hungry. Maybe not immediately, but eventually. Burn more calories and the odds are very good that we’ll consume more as well."

True. It makes me more hungry. But what about the differences exercise makes to physiology? Aren't there changes to the body that exercise causes? Other reading I have done point to an increase in metabolism and changes in body composition from more fatty tissue to more lean muscle mass which requires more fuel - even at rest.

Late in the article is this passage:

"Ultimately, the relationship between physical activity and fatness comes down to the question of cause and effect. Is Lance Armstrong excessively lean because he burns off a few thousand calories a day cycling, or is he driven to expend that energy because his body is constitutionally set against storing calories as fat? If his fat tissue is resistant to accumulating calories, his body has little choice but to burn them as quickly as possible: what Rony and his contemporaries called the “activity impulse”—a physiological drive, not a conscious one. His body is telling him to get on his bike and ride, not his mind. Those of us who run to fat would have the opposite problem. Our fat tissue wants to store calories, leaving our muscles with a relative dearth of energy to burn. It’s not willpower we lack, but fuel."

While I agree that we are "programmed" a certain way, I think this particular view overlooks the possibility of re-programming the body. This really is what training is all about. If you do certain things in training, you can improve your endurance, speed, and the distance you are able to run. If you don't do certain things in training, would you expect to be able to run faster? Further?

If you don't exercise, you can't train your body to utilize certain energy stored in your body. If you exercise certain ways, you train your body to utilize different types of fuel. There is a great book, Why We Run by Bernd Heinrich, which really delves into the physiology of running and endurance. It really is a fascinating book and very much worth a read. Or re-read.

Mr. Taubes points to aspects of diet that have a greater effect on weight loss - cutting candy, beer, soda, chips (all the stuff I used to eat in much higher quantities). I agree here too. And I think that diet does have a much more drastic affect on weight loss - it is easier to avoid eating 500 calories than it is to burn off 500 calories.

But how many people really maintain weight loss without exercise? I can't say that my weight would be where it's at without the running I do. At the same time, as is pointed out in the article, I did not get where I am at with exercise alone. I made significant changes to my diet and maintain those changes now. Mainly because it's much more healthy and allows me to do the things I want to do better.

He also says exercise can, and should, be done for other health benefits. Just not alone for the purpose of weight loss. It's an interesting read. Give it a read.

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