I admit my confirmation bias has exercise being a very minor contributor to a person's overall weight - at least in terms of a direct effect.
There's no doubt that exercise plays a major role in weight management, but I feel that it's primary role is to support a healthy living attitude. Anyone who's ever trained hard for anything knows it's a great deal easier to think about healthy eating and healthy habits when you actually feel health than when you don't, and exercise certainly confers a sense of health.
Of course not everyone shares my views and there are many folks who think I'm dead wrong and that exercise is the bomb for weight. Some of these folks have been pointing for a few days to a study published last month in the Journal of Epidemiology and Community Health as proof of their assertion.
The study looked at 12,227 men and women between the ages of 20-64 between the years 1999 and 2006 and compared their weights to their degree of leisure time physical activity.
The results?
Not exactly a slam dunk. They found what they called a "crude graded inverse
dose‑response relationship" between leisure time physical activity in women, but not men. Oh, and not all women, only white women.
Crude indeed.
So really, if anything, the study demonstrated that exercise correlated with decreased rates of obesity in white women and absolutely nobody else.
Of course even with white women, correlation does not imply causation.
Amazingly the authors didn't bother to control for the major variable of weight - diet.
Could it simply be that the white women who exercised the most also ate the best?
Sure sounds possible to me.
Could it simply be that lighter white women enjoyed exercise more simply because they were lighter and that the heavier a woman was, the less they enjoyed leisure time exercise and therefore the less they did of it?
Maybe.
And what happened with men? Or with black and Hispanic women? If exercise truly impacted on weight certainly you'd expect to see across the board significance, yet here, it's just white women.
Sorry Oprah.
Ultimately this study adds absolutely nothing to either side of the argument of exercise's role in weight management and its publication serves only to appease the confirmation biases of those folks who are exercise's true believers and to further shake my faith in peer review.
No doubt exercise is great for your health, no doubt exercise is crucial in maintaining weight loss, lots and lots of doubt that exercise alone in real world experiments does much to help lower or maintain weight, and this study doesn't do anything to dispel any of it.
Seo, D., & Li, K. (2010). Leisure-time physical activity dose-response effects on obesity among US adults: results from the 1999-2006 National Health and Nutrition Examination Survey Journal of Epidemiology & Community Health, 64 (5), 426-431 DOI: 10.1136/jech.2009.089680
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Right. Weight control management includes both physical activity and healthy eating through global healthy lifestyle. And I am agree that controling for food intake could make disappear the effect of exercise on wieght level in white women. Many studies have also demonstrated that obese people exercise less for many reasons. One of them is that even if they lose weight, they are still doing less exercise than lean people, putting them at high risk for weight regain. My point here in this article, is that white women who exercise have succeeded to prevent gain weight over the years as a life style, which is different to do exercise to lose weight as a secondary prevention of overweight management.
ReplyDeleteARG! First of all I have not read the study but it already proves inadequate by ignoring caloric intake. What measurements were used for weight? Probably a scale...an ancient method. Exercise has many forms and most people do not perform it effectively. For example, if a person becomes 40 pounds overweight, walking 3 miles a week will not stimulate enough oxygen increase to burn it off. However walking will slow continued growth and likely stimulate positive thoughts and behavior change in eating habits. Did the study include supervised exercise by trained instructors? Just like Opera's fine physique on the cover, fitness and weight management is easily achieved by anyone given the right leadership. The fact that she could sustain the exercise is another email. Even though Hispanic and black people metabolize more efficiently, we take advantage of their increased capacity to process calories during exercise and get amazing results. There a lack of knowledge about exercise and body fat. I have been using waist circumference, BF:Lean tissue and weight. Often patients do not lose much weight in the first phase of exercise due to a series of complicated physical demands to adapt to the increase stress of exercise. This translated into increased production of hemoglobin to muscle tissue, strengthening of the lower extremity joints and tendons, and fluid retention for heat management. The lager a person is, the greater the weight gain during the early phase. However, visceral fat is quickly accessed in this phase, especially when you have a deficit of calories. This is proven when waist circumference is (always) lower within four weeks of training. I saw an interesting study on obesityresearch.org about the exact areas of visceral fat that are both stored and accessed. I am confident that most people who are active and overweight access mostly visceral fat and never exercise efficiently enough or restrict diet long enough to access subcute fat stores. All I need is a scientist from the NIH to biopsy my patients before and after exercise!
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