Children's waist size points to risks

By KATHERINE HOBY

New Zealand children may be even fatter and more prone to future health problems than recent figures indicate.

Results of a British survey, conducted over three decades, suggest that the official way we have been measuring our children may underestimate obesity.

Body mass index (BMI) has been the most commonly used measure of overall obesity in both children and adults for years. The most recent survey, in 2001, showed that 14 per cent of the Auckland children surveyed were obese.

But the British research suggests waist circumference is a far better indicator of obesity, and as a marker for future health problems, including diabetes, heart problems and high cholesterol.

Auckland medical weight consultant Dr Anne-Thea McGill agrees.

"Not only are our kids getting fatter but they're getting fatter in the worst places," she says. "Fat around the waist [means] fat around the heart."

She says waist circumference is a marker for central body fat accumulation. A large waist circumference is linked to an increased risk of metabolic complications.

The research, published in the British Medical Journal in March, surveyed 3784 children aged 11-16 years in 1977, 1987 and 1997. It compared BMI and waist circumference measurements.

It concluded that trends in waist circumference during the past 10 to 20 years have greatly exceeded those in body mass index, particularly in girls. This shows that BMI is a poor indicator of central fatness.

"Body Mass Index has therefore systematically underestimated the prevalence of obesity in young people," it reads.

"Current and future morbidity in British youth may be seriously affected due to accumulation of excess central fat."

Dr McGill says traditional obesity rates depend on BMI only.

"We need to go a bit further and get a bit smarter," she says. "We need to measure the things that really matter. Measuring around the middle is going to tell you far more about who's in for a bad time."

Obesity is an epidemic in New Zealand children and real indicators on numbers are needed, she says.

"We need to know the hard truth. We need to know what we are up against."