Physical Inactivity doesn't Cause Childhood Obesity

More than 12 million children and adolescents are considered obese, according to a report titled F as in Fat: How Obesity Threatens America's Future 2010 released on June 30 by Trust for America's Health and Robert Wood Johnson Foundation.

The 2007-2008 National health and Nutrition Examination Survey also revealed 17 percent of American children and adolescents aged 2 to 19 years are obese.

Childhood obesity is associated with a variety of health conditions such as cardiovascular disease, high blood pressure, high cholesterol, and Type 2 diabetes.

How can we prevent childhood obesity then?

Obesity results from an imbalance between energy intake and energy expenditure. That is, if you eat more than what you need, you gain weight or fat.  Therefore, there are two ways to prevent obesity, lowering energy intake and increasing energy expenditure.  The latter is associated with increased physical activity.

Often times, eating less is not encouraged.  If you and everyone else eat 1% less, the industry will suffer a loss in profit.  So health officials often stress that individuals need to engage in adequate physical activity.

Physical activity can be surely expected to help prevent obesity, but physical inactivity should be blamed for obesity.

That is what Metcalf B.S. and colleagues from Peninsula Medical School in Plymouth, United Kingdom suggested.

Metcalf et al. published their longitudinal study in the June 23, 2010 issue of Archives of Disease in Childhood saying fatness leads to physical inactivity, but inactivity does not necessarily lead to fatness.

In the study, the researchers followed 202 children of whom 25 percent were overweight or obese for 7 to 10 years. 

During the follow-up, the children were asked to wear Actigraph accelerometers for seven days a year to measure their physical activity.  The body weight of each child was measured annually using dual energy x ray absorptiometry.

The researchers found the body fat percentage was predictive of changes in physical activity over the following 3 years, but physical activity levels were not predictive of subsequent changes in body fat percentage over the same follow-up period.

They concluded "Physical inactivity appears to be the result of fatness rather than its cause. This reverse causality may explain why attempts to tackle childhood obesity by promoting physical activity have been largely unsuccessful."

By Jimmy Downs