The childhood obesity window is closing: Genetic influence of height and weight grows as we get older

April 23, 2014, Medical Daily

By Matthew Mientka

A new study on twins shows the importance of early intervention as America’s childhood obesity rate continues to rise after doubling during the past 30 years, with more than one-third of children overweight and obese.

By comparing data collected on more than 2,500 pairs of twins with genomic analysis, researchers from King’s College London and the University of California, Los Angeles (UCLA), got a pretty good look at the interplay between nature and nurture. They found the influence of genetics on individual differences in body mass index (BMI) rose from 43 percent at age 4 to 82 percent by age 10, suggesting parents and clinicians might intervene with improved diet and lifestyle choices at earlier ages — when the time is ripe.

“Our results demonstrate that genetic predisposition to obesity is increasingly expressed throughout childhood,” UCLA researcher Clare Llewellyn said in a press release. “This underlines the importance of intervening at an early age to try to counteract these genetic effects and reduce childhood obesity.”

The study supports previous work showing a doubling of genetic influence — or heritability — over BMI as children grew through early childhood. Llewellyn and her colleagues say the rising influence of genetics through childhood might be explained by “gene-environment correlation,” a process describing the tendency of children as they grow to seek new environments outside the home to “express their genetic predispositions.”

In the study, the researchers first executed a genome-wide complex trait analysis estimating the combined effects of more than 1.7 million common genetic variants throughout the human genome, finding the influence of these common genes increasing by 50 percent between ages 4 and 10. But since that analysis fails to identify the action of specific genes, they devised a metric from 28 genetic variants known to be linked to heightened risk for obesity, which confirmed their findings.

The import of these studies is enormous for the future health of populations around the globe as children with obesity suffer immediate health concerns such as hypertension and high cholesterol, risk factors for the development of heart disease. As many as 70 percent of children ages 5 to 17 in one population-based survey carried at least one risk factor for heart disease, Llewellyn says.

And as they grow into adolescence, such children are more likely to develop prediabetes, as blood glucose levels rise to put them at future risk. Moreover, heavier kids tend to experience sleep apnea and more bone and joint ailments, aside from the usual social stigmatization and poor self-esteem.

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