KEY POINTS:
Auckland University research has revealed that short bursts of sprinting do little to protect young children from packing on the weight, but switching off the television - and being a boy - is a big help,
The new research on 591 children aged 7 shows their amount of sedentary behaviour is more important than vigorous activity in shaping their bodies. And importantly, the research, part of a long-term study that began with 871 children born 10 or 11 years ago, confirms that weight patterns are set early in life.
"Our finding that percentage of body fat at 3.5 years is strongly related to percentage of body fat at 7 years provides further evidence that many start on the trajectory to overweight and obesity early in life and that interventions need to start early," says the research paper, published in the Archives of Disease in Childhood.
The study found those born to obese mothers had 4 per cent more body fat than those whose mothers were not obese or overweight.
Those who watched more than three hours of TV daily had 5.2 per cent more body fat than those who switched off within one hour. New Zealand children on average watch two hours 11 minutes of TV a day.
The study found that for every extra hour per day of sedentary activity during waking hours, children had 0.8 per cent more body fat.
Girls had 1.8 per cent more body fat than boys.
"Sedentary behaviour was shown to be a risk for being overweight, whereas we weren't able to show vigorous activity was protective," one of the researchers, Professor Ed Mitchell, said yesterday.
"It's quite striking how little vigorous activity the 7-year-olds do. They don't run for half an hour. Most of their activity is done in tiny, 1-to-2-minute bursts. They spend large chunks of time sitting down."
The children wore "accelerometers" - akin to pedometers - to measure their movement.
Professor Mitchell wonders if vigorous activity will show up as protective in results from checks on the children as 11-year-olds.
Asked the possible reasons for girls' greater fat levels, he said: "We certainly know that after puberty girls have more fat than boys. That's just the way it is. We hadn't really expected it at 7 when they are pre-pubertal."
He said one of the main findings was the strong correlation between being overweight at 3 1/2 and at 7, which was important because it was already known that the problem tended to persist from school years into adulthood.
"Everyone puts it down to 'puppy fat' and thinks it will disappear, but this is clearly not the case," Professor Mitchell said.
Findings on diet will be published later.
