Is Childhood Obesity Due to Not Enough Exercise?

As any reader of The Shangri-La Diet knows, I attribute the obesity epidemic to ditto foods — foods that taste exactly the same each time, such as factory food and fast food. We eat a lot more of these foods today than 50 years ago or even 20 years ago.

An alternative explanation of the obesity epidemic that many people believe is too little exercise. People who deal with childhood obesity, in particular, often say the problem is too much TV, too little playground.

If kids are fat due to lack of exercise, more exercise should be a good solution. A new study shows it isn’t. It turns out that giving kids more P.E. doesn’t cause weight loss:

In studies involving nearly 10,000 children, primarily in elementary schools, none demonstrated a reduction in BMI with those who were assigned to the most phys-ed time, compared to those who didn’t have as much.

Via Calorie Lab.

10 Replies to “Is Childhood Obesity Due to Not Enough Exercise?”

  1. I find this result entirely unpersuasive. My recollection of P.E. classes is that they mostly amounted to standing around waiting, with a total of less than ten minutes of movement in any given class period. Such a signal is completely swamped by how far a kid has to walk to the bus stop, never mind whether they ride their bike after school.

  2. Well, it seems obvious that the students did get more activity since the ones who had more physical activity had “improvements to bone mineral density, aerobic capacity, reduced blood pressure and increased flexibility.”

    It would probably be best to look at the details of the actual study to see just how much more activity the students got before dismissing it based on your memory of phys ed classes.

  3. The obesity pandemic is certainly out of hand and children today are being brought into a world of processed foods with little nutrition. With the digital age in full force, and less ‘labor’ being performed, the calorie expenditure has declined tremendously. It’s easy to get more calories into the diet, and easier to expend few calories, and that adds up to trouble for the health of our country now and for the next generation. We may start seeing heart disease and heart attacks in teenagers very soon. It’s not unthinkable that we may be making ourselves extinct considering the course the world is on. It takes moving back to nature – fruits, vegetables, hard work. Science may never be able to duplicate what nature perfected long ago.

  4. I think that there are many factors that contribute to it, and changing just one or two at a time is not enough to reach a tipping point to reverse it.

  5. I believe there is good epidemiological evidence to show that the rather sudden rise of childhood obesity in the US coincided with the recommendations to lower fat consumption and eat more carbs. IIRC this is documented in Taubes’ “Good Calories; Bad Calories.” The reason, as Taubes explains in much more detail, is that the body can only store fat in the presence of insulin and carbs cause a rise in insulin.

    This evidence doesn’t negate the possibility that the “ditto foods” setpoint theory could also account for at least part of the rise.

    High-calorie, high carb foods are especially addictive as well as fattening since the “sugar rush” from the carbs coupled with the high calories increases their addicive power.

  6. BMI is a very poor measure. It does not take into account muscle gained through exercise. It lists bodybuilders with 6% body fat as obese and fat people with little muscle as normal. Heavy kids running around in P.E. are going to gain muscle just due to the weight that they are not used to moving around.

    I know for me that when I exercise that it makes me eat more. This study does not show that exercise does not work; it just shows that it is not sufficient, at least at the intensity level of a P.E. class. Diet is probably the more important factor.

  7. A daily PE requirement (as Florida recently adopted) is a good idea if only for the benefits to mental health (see John Ratey’s new book “Spark”).

    This study reminds me of two from the 90’s that Gina Kolata mentioned in Rethinking Thin– and in in a 2006 NY Times article she wrote (quoted below). Kolata makes the point that since the current worldview (fad, frame, paradigm, whatever you want to call it) is that modifying children’s diet and exercise schedule is the best way to reduce childhood obesity, no one wants to hear about evidence that it doesn’t make a difference in terms of weight loss. A fine example of cognitive dissonance for your Psych students, Seth. :o)

    “In the 1990’s, the National Institutes of Health sponsored two large, rigorous studies asking whether weight gain in children could be prevented by doing everything that obesity fighters say should be done in schools — greatly expand physical education, make cafeteria meals more nutritious and less fattening, teach students about proper nutrition and the need to exercise, and involve the parents. One study, an eight-year, $20 million project sponsored by the National Heart, Lung and Blood Institute, followed 1,704 third graders in 41 elementary schools in the Southwest, where students were mostly Native Americans, a group that is at high risk for obesity. The schools were randomly divided into two groups, one subject to intensive intervention, the other left alone. Researchers determined, beginning at grade five, if the children in the intervention schools were thinner than those in the schools that served as a control group.

    They were not. The students could, however, recite chapter and verse on the importance of activity and proper nutrition. They also ate less fat, going from 34 percent to 27 percent fat in their total diet. Alas, said the study’s principal investigator, Benjamin Caballero, director of the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health, “it was not enough to change body weight”…

    The paper appeared in The American Journal of Clinical Nutrition in 2003 to no acclaim, Dr. Caballero said. No press release, no media coverage, no invitations to speak about the results at scientific meetings. On the journal’s Web page, a search of articles that refer to the study comes up empty. It has not been cited anywhere.

    The second study, of 5,106 children in 96 schools in California, Louisiana, Minnesota and Texas, had a similar design and the same results: all that help made no difference in the children’s weights.”

  8. That’s the sort of valuable information in Rethinking Thin that makes me so very disappointed in Kolata’s shallow, misguided take on Taubes in her NY Times book review, and her response to Taubes’s response to it.

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