Dizzying Contradictions in Childhood Obesity

Kid's Always Eating Something

We saw how fathers can genetically influence the weight of their children, or at least the weight of their daughters, as shown by an Australian study.

Medical Xpress recently wrote about the work being done at University College London with genome-wide complex trait analysis, or GTCA. This is a technique that “estimates the combined effects of all known common genes across the whole genome, associated with childhood body weight.”

The subjects were 2,269 children aged 8 to 11. The study’s lead author, Clare Llewellyn, of the Health Behaviour Research Centre, is quoted as saying:

These findings are important because they confirm that in children genes play a very important role in determining body weight. At present only a few genetic variants have been discovered, and these explain a very small amount of individual differences in body weight (~2%). These findings suggest there are hundreds of other genetic variants influencing body weight that are yet to be discovered.

The article explains the concept of “missing heritability,” saying:

32 genes have been identified as risk factors for obesity but previous analyses suggest that these genes alone cannot fully explain the high level of heritability in childhood obesity, as together they explain only 2% of individual differences in childhood body weight.

Four genes associated with severe childhood obesity were discovered by a Wellcome Trust Sanger Institute study whose first author is Dr. Eleanor Wheeler, who is quoted by Science Codex:

We’ve known for a long time that changes to our genes can increase our risk of obesity. For example, the gene FTO has been unequivocally associated with BMI, obesity and other obesity-related traits. In our study of severely obese children, we found that variations in or near two of the newly associated genes seem to have a comparable or greater effect on obesity than the FTO gene…

The article also quotes co-lead author, Professor Sadaf Farooqi, of the University of Cambridge:

Some children will be obese because they have severe mutations, but our research indicates that some may have a combination of severe mutations and milder acting variants that in combination contribute to their obesity.

The other co-lead author, Dr. Inȇs Barroso, of the Wellcome Trust Sanger Institute, says:

Our study adds evidence that a range of both rare and common genetic variants are responsible for severe childhood obesity.

But then, other scientists maintain that genetics count for very little, and the obesogenic environment is the main villain, or rather comprises a whole collection of villains — fast food on every corner, technological innovations, hardly anyone cooking at home anymore, cheap junk food, giant sugary drinks, vending machines, etc., etc.

Scientific American writer Tara Haelle says:

New evidence is confirming that the environment kids live in has a greater impact than factors such as genetics, insufficient physical activity or other elements in efforts to control child obesity. Three new studies, published in the April 8 Pediatrics, land on the import of the ‘nurture’ side of the equation and focus on specific circumstances in children’s or teen’s lives that potentially contribute to unhealthy bulk.

Three studies are mentioned here, chosen from a larger number of possible indictments. One study found that the size of the plate on which food is served makes a difference. Going against the theory that obesity is a disease of inactivity, Prof. David Bickham, Harvard Medical School, says that video games and computer screen time have no effect on a child’s body mass index, and television only does if watching it is the main activity and the child isn’t doing something else at the same time. Another study explored sleep, and found that if teenagers would get more of it, they would be less obese.

The writer also quotes Dr. Yoni Freedhoff, the University of Ottowa, who says:

This is a lot more complicated than ‘eat less, exercise more. If weight management or childhood obesity prevention and treatment were intuitive, we’d have a lot of skinny kids running around. If we had a time machine, it would be the world’s best weight-loss program. It’s the world that has changed, not people.

Your responses and feedback are welcome!

Source: “Study finds strong genetic component to childhood obesity,” Medical Xpress, 03/26/13
Source: “Finding genes for childhood obesity,” Science Codex, 04/07/13
Source: “Consumption Junction: Childhood Obesity Determined Largely by Environmental Factors, Not Genes or Sloth,” Scientific American, 04/09/13
Image by Aaron McIntyre.

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