Genetic test can identify kids likely to become obese

By Stephen Beech

Children likely to become obese in adulthood can be identified by a new genetic test.

Scientists say the test, based on data from more than five million people, can be performed on youngsters before their genetic risk starts to determine their weight.

The World Obesity Federation expects more than half the global population to be overweight or clinically obese by 2035.

An international team of researchers created the genetic test - called a polygenic risk score (PGS) - that predicts adulthood obesity in early childhood.

They say their findings, published in the journal Nature Medicine, could help to identify children and teenagers at higher genetic risk of becoming obese, who could benefit from targeted preventative strategies - such as lifestyle changes - at a younger age.

Assistant Dr. Roelof Smit, from the NNF Centre for Basic Metabolic Research (CBMR) at the University of Copenhagen, Denmark, was the study lead author.

He said: “What makes the score so powerful is its ability to predict, before the age of five, whether a child is likely to develop obesity in adulthood, well before other risk factors start to shape their weight later in childhood.

"Intervening at this point can have a huge impact.”

The study arises from the Genetic Investigation of Anthropometric Traits (GIANT) Consortium, an international collaboration of human genetics researchers dedicated to studying the genetic architecture of traits such as human height and body mass index (BMI).

The research involved a collaboration with the consumer genetics and research company 23andMe, inc., and the contributions of more than 600 scientists from 500 institutions around the world.

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The team explained that subtle variations in our genomes can greatly impact health and well-being.

Thousands of genetic variants have been identified that increase the risk of obesity, including variants that act in the brain and influence our appetite.

Dr. Smit says a PGS is like a calculator that combines the effects of the different risk variants that a person carries and provides an overall score.

To create their PGS, the research team drew on the genetic data of more than five million people – the largest and most diverse genetic dataset ever.

The researchers then tested their new PGS for obesity on datasets of the physical and genetic characteristics of more than 500,000 people.

They found that their new PGS was twice as effective as the previous best test at predicting a person’s risk of developing obesity.

Dr. Ruth Loos, also from CBMR at the University of Copenhagen, said: "This new polygenic score is a dramatic improvement in predictive power and a leap forward in the genetic prediction of obesity risk, which brings us much closer to clinically useful genetic testing."

The research team also investigated the relationship between a person’s genetic risk of obesity and the impact of lifestyle weight loss interventions, such as diet and exercise.

They discovered that people with a higher genetic risk of obesity were more responsive to interventions, but also regained weight more quickly when the interventions ended.

But the research team said the new PGS has limitations.

Despite drawing on the genomes of a broader, more globally representative population, the team found it was far better at predicting obesity in people with European-like ancestry than in people with African ancestry.