Environment Shapes Kids' Physical Activity

Home, School Settings May Be a Bigger Influence Than Genes

From the WebMD Archives

Oct. 12, 2005 -- Ever wonder why some kids flock to physical activity -- and how to encourage those habits in other children?

Then you might want to pay attention to the setting in which kids live, learn, and play.

Kids' physical activity level may depend more on their environment than their genes, new research shows.

That is, what kids experience and are encouraged to do may be the bigger influence on physical activity.

The report appears in The American Journal of Clinical Nutrition.

Why It Matters

With childhood obesity on the rise and bringing with it the risk of developing other medical problems early on, it is important to gain as much information as possible so that we can prevent this from happening in our children.

Most health experts agree that it's a good idea for everyone -- young and old -- to be physically active. But a lot of people don't heed that advice.

Why is that? Is it due to our genes or a lazy lifestyle? It's a key question, especially for kids, who may be shaping lifelong patterns.

"Determining why children are becoming physically inactive is important because sedentary behavior is a strong independent risk factor for metabolic diseases such as obesity and diabetes," researcher Paul W. Franks, PhD, tells WebMD.

Habits formed in childhood can be changed, but doing so isn't always easy. "Childhood behaviors track through to adulthood," writes Franks.

He is a member of the Genetics Group at the Elsie Widdowson Laboratory in Cambridge, England. Franks worked on the study while on staff at the U.S. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Twin Study

Franks' study included 100 sets of U.S. twins who were 5 to 10 years old. The group included 38 sets of identical twins and 62 pairs of nonidentical (fraternal) twins.

Identical twins have identical genes. Nonidentical twins have half of their genes in common. Twins are often raised in the same setting. By studying twins, researchers can track genetic and environmental influences.

The kids' physical activity, body composition, and energy burned while at rest were measured with "gold-standard methods," notes Franks. "These features made this study unique from studies published elsewhere."


Genes or Environment?

Genetic factors explained much of the difference in kids' body composition and resting energy expenditure, the study shows.

But genes apparently didn't account for kids' physical activity level.

"The shared environment (e.g., the school and home environment) explained a large proportion of the variance in physical activity," says Franks.

That is, kids' environment was a bigger influence on physical activity than genes.

Learning to Be Active

"This indicates that the tendency of the children in our study to move around and be physically active was not determined by their genetic constitution, but by the influence of the people and the environment to which both twins were exposed," writes Franks.

By the way, "environment" doesn't just mean the physical setting in which kids live. The example and outlook of grown-ups probably also counted.

"This likely includes the attitudes and actions of friends, family members, and school teachers," writes Franks.

Boosting Physical Activity

It should be possible to boost kids' physical activity, says Franks.

"These observations support the view that the trend toward physical inactivity observed in children in the U.S. is modifiable, but that successful preventive strategies may need to focus not only on the children, but also on many aspects of the home and school environment," writes Franks.

In other words, if you want kids to be more active, design their lives to encourage physical activity at home and at school.

Model Behavior

Why not join kids in becoming more physically active? You'd become a role model while tending to your own health.

The CDC recommends that kids and teens get at least 60 minutes of moderate-intensity physical activity on most days of the week (preferably, daily).

The CDC recommends that adults get at least 30 minutes of moderate-intensity physical activity five or more days per week.

Check in with a doctor before starting a new exercise program.

WebMD Health News Reviewed by Louise Chang, MD on October 12, 2005


SOURCES: Franks, P. The American Journal of Clinical Nutrition, October 2005; vol 82: pp 901-908. Paul W. Franks, PhD, Genetics Group, MRC Epidemiology Unit, Elsie Widdowson Laboratory, Cambridge, England. CDC: "Physical Activity for Everyone: Recommendations: Are there special recommendation for young people?" CDC: "Physical Activity for Everyone: Recommendations."

© 2005 WebMD, Inc. All rights reserved.


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