Thursday, October 11, 2007

Will Increased Activity Lead To Weight Loss?

"No," says Gary Taubes.

Ruby, RB, Melinda, and others commented about exercise and its role in weight loss. Gary Taubes, author of the recent book, Good Calories, Bad Calories, addressed this in his interview with New York Public Radio a few weeks ago:
"Exercise makes you hungry. It does not make you lean."
- Gary Taubes, WNCY, The Brian Lehrer Show, September 17, 2007
I was aware of a compensatory mechanism for physical activity ... the more we exercise, the hungrier we become, the more we eat. But I was not aware that, as Taubes argues, increased activity would not contribute to weight loss.

RB, in that interview you mentioned, where Taubes, Ornish, and a representative of the American Heart Association (AHA) were discussing variables that lead to obesity, you noted that only the AHA rep., Dr. Howard, brought up physical activity. I noted that too. Since exercise is a part of every weight loss program I've ever come across, I wondered where exactly Ornish, Atkins, and others stood.

(I'm only going to focus on exercise as it relates to weight loss. There are many aspects of health that exercise has been shown to impact.)


Although Dr. Dean Ornish advocates a low-fat diet, that's not the only aspect of his program. His heart studies implemented the "Intensive Lifestyle Changes" program, which included exercise, for heart disease reversal. But here is what he said would constitute a good approach for everyone:
"The diet for preventing illness, losing weight, and just feeling good is much less restrictive. ... I recommend moderate exercise. The more you exercise, the more fit you become, but not necessarily the healthier you become. Just walking 20 or 30 minutes a day and not even all that fast can reduce premature death by 50% or more."
- Dr. Ornish, Heart-Healthy Lifestyle Program


Although Dr. Robert Atkins advocated a reduction in carbohydrates, that was not the only aspect of his program. He also recommended exercise:
"Calling all couch potatoes: If you're not getting regular exercise, you aren't following the Atkins Nutritional Approach. It's that simple."

"Exercise has enormous benefits for your health, and will speed your weight loss!"

"Regular physical activity has been proven to contribute significantly to weight loss, weight maintenance, good health and disease prevention."

"For example: Without changing the way you eat, say you burned an extra 250 calories per day, which a 150-pound person could accomplish by walking for about forty-five minutes at a pace of three miles per hour. If you did this for two weeks, you would create a deficit of 3,500 calories and thereby lose 1 pound of body weight."
- Dr. Atkins' New Diet Revolution

American Heart Association

The American Heart Association advocates the "Therapeutic Lifestyle Changes" diet. This is the program developed by the government's National Heart, Lung, and Blood Association’s National Cholesterol Education Program (NCEP):
"Daily energy expenditure should include at least moderate physical activity (contributing about 200 Kcal a day)."
- AHA, Heart-Healthy Diets
Just to interpret that "200 Kcal/day", here's a link to a tool that will calculate how many calories you might expend walking, based on your weight, how fast you walk, and for how long. (The food they come up with that equals the calories you burned is, well, you'll see.):

AHA recent advice:
"Women who need to lose weight or sustain weight loss should accumulate a minimum of 60 to 90 minutes of moderate-intensity physical activity (eg, brisk walking) on most, and preferably all days of the week."
- Evidence-Based Guidelines for Cardiovascular Disease Prevention in Women: 2007 Update


Gary Taubes questioned the belief that weight gain is caused by inactivity (or by overconsumption). He looked at the research and stated:
"... any increase in energy expenditure will have to induce a compensatory increase in intake, and so hunger has to be a consequence. And any enforced decrease in intake will have to induce a compensatory decrease in expenditure - a slowing of the metabolism and/or a reduction in physical activity."

"... neither eating less nor exercising more will lead to long-term weight loss, as the body naturally compensates."

"Running marathons, however, will not make fat people lean, even if they can get themselves to do it, because their bodies will adjust to the extra expenditure of energy, just as they would adjust to calorie-restricted diets."
He concluded:
"Obesity is a disorder of excess fat accumulation, not overeating, and not sedentary behavior."

"Expending more energy than we consume does not lead to long-term weight loss; it leads to hunger."
- Gary Taubes, Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control and Disease
In sum:
  • Ornish recommends exercise for weight loss.
  • Atkins recommends exercise for weight loss.
  • The AHA recommends exercise for weight loss.
  • Taubes says exercising more will not lead to weight loss.
In fact, Taubes and Atkins are diametrically opposed here. Atkins says that if you hold intake constant and increase activity, weight loss will follow. Taubes says that if you hold intake constant and increase activity, hunger and a slowed metabolism will follow ... which will stymie weight loss.

I agree with Gina Kolata's characterization of Taubes (in her review of his new book) as a "brave and bold science journalist". It certainly is brave to suggest that an increase in physical activity will not encourage weight loss. I think Taubes' assertion is unfortunate, since it may set us down a slippery slope of less, not more, activity. And I believe physical activity is beneficial for health in so many ways.

Update: If you'd like to read more and you don't have his book handy, Gary Taubes published an article in last week's New York magazine that explains his reasoning: "The Scientist And The Stairmaster: Why Most Of Us Believe That Exercise Makes Us Thinner - And Why We're Wrong".

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