March 5th, 2012

New Insight Into Obesity and Physical Activity in Children

As obesity has increased among children, a clear link has been established between obesity and cardiovascular risk factors including high cholesterol, high blood pressure, and diabetes. However, less is known about whether being more physically active might protect children from developing these risk factors. Among adults, physical activity has been shown to reduce cardiovascular risk and prolong life regardless of whether a person is obese or non-obese. Less is known about how these factors work together in children.

A recent study in JAMA by Ekelund and colleagues is one of the first to directly address this question of whether physically active children have better cardiovascular health compared with less active children. It is a particularly powerful study because it analyzes the combined results of several studies to include over 6,000 children. The key findings are that moderate and vigorous physical activity (MVPA) is strongly linked to lower cardiovascular risk, that time spent sedentary is not directly linked to cardiovascular risk, and that relatively small differences in physical activity levels can have a profound impact on cardiovascular health. The study also found that physical activity and sedentariness interact in an interesting way. Specifically, children who were the most physically active and the least sedentary had lower cardiovascular risk compared with similarly active but more sedentary children.

This means that interventions that attempt to increase physical activity levels and to decrease sedentariness might have a greater effect on cardiovascular health than attempts to change either behavior alone. In addition, the results suggest that increasing children’s MVPA by only 20 minutes might significantly improve their health regardless of its impact on their weight. Thus, this study provides evidence of the urgent need to identify children who are less physically active and invest in large scale public health efforts to increase active play and reduce sedentariness.

2 Responses to “New Insight Into Obesity and Physical Activity in Children”

  1. Karen, nice summary of an interesting topic. As a geneticist, I’m often asked how we can discover the “obesity gene” that is responsible for making children gain weight. But there isn’t one. I believe that the etiology of the “obesity epidemic” is entirely cultural. Our gene pool has not changed much, but the culture of childhood certainly has. When I was growing up in the 1970s, kids were free-ranging outdoor creatures with lots of unstructured time. We all played together and went home when the streetlights came on. It seemed safe at the time, but it really wasn’t. There were accidents, even drownings and deaths by falling. Pedophiles trolled the streets in vans with dark windows. Kids committed violent crimes and damaged property. All that social pathology has declined sharply since I was growing up. Accidents, sexual abuse and child abduction by strangers, and juvenile offenses have all dropped precipitously in frequency over the last several decades. Why? Parents (and schools) got the media message to keep kids under constant surveillance for safety’s sake, and for most kids, safety is tantamount to being under house arrest. Affluent parents have found ways to keep their kids lean – the prep school kids still look like fleets of svelte gazelles on the lacrosse fields. But disadvantaged parents lack the education and resources to follow suit. My hypothesis is that physical fitness has been sacrified for greater safety. To the extent that this hypothesis is true, then the solution will either involve some loss of safety or else the expenditure of social resources on safe physical fitness activities for families that can’t afford them.

  2. Karen Politis, MD says:

    I grew up in the “dangerous” days. playing, riding our bikes, coming home dirty and hungry. Sure, we had accidents, but no one suffered permanent harm. My daughter of the “safe” generation, now 25, has already lost several classmates in traffic accidents. Most safety measures i.e. preventing drownings, can be implemented without keeping children cooped up in the house. Give the children more time and room to play, and – this is the difficult part – get them away from TV and computer screens.