31 Jul 2014

Childhood Obesity

From Our Changing World, 9:06 pm on 31 July 2014

We hear a lot about rising rates of obesity in adults, but in New Zealand, childhood obesity is an even more worrying issue. Obesity in young children and teenagers is increasingly recognised as a precursor to major adult diseases such as diabetes and heart disease, even if the weight problem itself does not continue into adulthood.

According to Ministry of Health figures, one in every three children in New Zealand is either overweight (22%) or obese (11%), and the rate of childhood obesity has increased from 8% in 2006 to 11% in 2013.

Paul Hofman, a paediatrician at the Liggins Institute, tells Veronika Meduna that he sees some of the worst cases, including teenagers who weigh between 150 and 200kg. As a consequence of their weight, these young people are already pre-diabetic or diabetic and suffer from fatty livers, sleep apnoea and heart problems.

Research at the Liggins Institute has shown that many aspects of a child’s physiology are programmed before birth and influenced by the mother’s diet, and Paul says the same applies to childhood obesity. This is also supported by the statistics of obesity, which show that adults (in the US) were becoming more obese from the 1960s, while American children only started to show weight issues from the late 1980s. “So there’s a delay of about a generation.”

Paul Hofman says research also shows that maternal weight before conception is a major predictor of a baby’s birthweight, suggesting that “somehow the excess nutrition [the babies] get from the mother sets them up to be more likely to become obese”.

‘So you get into this situation of obesity begetting obesity, and it’s not genetic, it’s environmental. If we can break that down, if we can reduce the amount of nutrients getting to the child during pregnancy, perhaps, just perhaps, we can modify that obesity risk and reduce the risk for the next generation.’

Childhood obesity tracks, says Paul Hofman, and an obese youth has a six to seven times higher risk of becoming an obese adult.

In order to break the obesity cycle, his team has been conducting trials that target pregnant women (of normal or access weight) to see if regular, supervised exercise can reduce the birth weight of their children. In one trial, normal-sized pregnant women who exercised up to 40 minutes each day had babies who were 250g lighter on average. These children are now eight years old and the team is in the process of analysing their risk of obesity. In another trial underway at the moment, obese pregnant women are exercising to see if this can modify the outcome for their children in the long term.

Earlier this year, Our Changing World featured an interview with University of Otago neuroscientist Christine Jasoni,  who is investigating how maternal obesity affects the formation of the baby's brain.