Exercise alone is no cure for childhood obesity

Our kids are getting fat - so fat that the Education Minister has ordered extra exercise in all schools. Lindy Andrews asks: Will it work? And just why are our kids piling on the kilos?
Ask David how much he weighs and the 15-year-old shifts uncomfortably from one foot to the other, before lowering his head and mumbling an embarrassed reply.
Standing 175cm tall, he tips the scales at 96kg.
To quote Garfield, the cartoon cat, the Tauranga teen is "too short for his weight".
In medical terms, David is simply obese; a young man potentially facing type-2 diabetes, heart disease and joint problems in later life.
David doesn't want his real name used - and that's perfectly understandable.
The Otumoetai College pupil has been ridiculed by his peers most of his life.
At birth, he was the model Plunket baby; entering the world at a chubby, contented 4.1kg.
David was "a hungry baby", his mum Sarah recalls and by two months of age, he had downed his first solids.
The chubby, contented baby grew into a chubby, contented toddler.
Within a few years, that changed.
But the time David was eight, he weighed 7.2kg more than his playmates of a similar height.
Sarah wasn't too worried. Puppy fat, she thought, was something he would soon grow out of.
Meanwhile, David was subjected to cruel playground taunts like "fatso" and "lard-arse". His self esteem plummeted and has never recovered.
Today, he is a reluctant sportsman, skiving off from physical education whenever possible and preferring the company of his PlayStation to more social pursuits.
Now, Sarah wonders if she should, or could, have been more proactive in managing her son's weight.
This week, Education Minister Trevor Mallard unveiled a multi-million dollar plan to pre-empt childhood obesity by topping up schools' existing physical education programme with a full hour of physical activity each week.
The move has been met with unbridled enthusiasm by the National Heart Foundation and clinicians concerned at the country's burgeoning diabetes and heart disease statistics.
Once considered diseases of the elderly, diabetes and dangerously-high cholesterol are fast-growing problems among people in their teens and 20s.
Hardest hit are young Pacific Islanders and Maori. Heart disease and type-2 diabetes have been linked to inactivity, obesity and high-fat, low-fibre diets.
But the reasons for the increase in those diseases among our young people are far more complex than food intake versus physical activity, says Tauranga paediatrician, Hugh Lees.
Obesity is not a problem for most people, he says, but growing numbers of obese children are being referred.
"They are small in number but the degree of obesity is significant."
Convenience and processed foods, television, PlayStations and a generally more sedentary lifestyle can take some of the blame, Lees says, but he doubts an hour's extra exercise each week will resolve what has become an increasingly complex health issue.
"It's well intentioned but the forces driving obesity are complex - is an hour's exercise going to reverse that?"
For example, the bodies of Maori and Pacific Island children, Lees points out, are genetically programmed to make the most of their food intake. In short, they are predisposed to becoming overweight, even when they might eat no more than the average Pakeha child.
Maori and Pacific Islanders - the majority of whose forebears were living a primitive hunter-gatherer lifestyle just 250 years ago - are still programmed to weather famine by storing more body fat when food is plentiful.
Our fast-paced lives also have to take some blame for creating this chubbier, unhealthier new generation.
Obesity - or, for that matter, being dangerously underweight - also has an emotional component.
"Societal change is the corollary of all this," declares Lees, who is also seeing increasing numbers of young anorexics.
"We're getting both ends of the scale."
These days, protective parents quiver at the thought of their kids walking or cycling to school, preferring to taxi them to the school gate.
Lees concedes American figures which show US children get 70 per cent less exercise than their parents or grandparents are probably reflected in New Zealand's young people.
Exercise, he says, needs to become part of Kiwi family culture, with plenty of fresh fruit and vegetables and modest amounts of protein and fats.
Icecream, chocolate and fast food need to take more of a back seat, rather than being a daily occurrence.
Rather than putting obese children on diets, Lees prefers to let them "grow into" their extra weight over one or two years.
Dieting brings its own set of problems, potentially causing malnutrition and future eating disorders.
"Most of the time children have the advantage of growth on their side," he explains. "If a child is 10, they have a lot of height to gain. If their weight remains static, they'll slim down with growth."
But, he warns, anyone who thinks their child is overweight should see a doctor before taking action. Weight gain can sometimes have nothing to do with over-eating or under-exercising.
Girls approaching puberty, for example, gain body fat naturally. It's part of the hormonal changes that create the ultimate, womanly shape.
Paul Hofman, a paediatric endocrinologist at Auckland's Starship Hospital agrees that childhood obesity is an extraordinarily complex issue.
There are two primary reasons why people get fat - food intake versus expenditure. But genetic disposition is another cause, he says. And inactivity.
A study of Japanese children showed a direct correlation between obesity and families that owned two cars. But, Hofman suspects, there may be other causes science hasn't yet fully explored.
Carbohydrates, fat and protein all play a role in our health but while researchers know plenty about the big food picture they're still very much in the dark when it comes to the finer details.
"There is less good evidence about nutrition," Hofman says.
"You can go on about McDonald's and about KFC - there is no question they're not ideal nutrition - but if you look at ourselves and our parents, we ate a huge amount of fat," Hofman says.
And Kiwis remained slender by comparison, despite feasting on such delights as butter, full-fat milk, hefty servings of red meat and bread fried in dripping.
Our increasing preference for time-saving, "low-fat" processed food may also have a role in obesity.
"Changes in the micronutrients like folate and vitamins may have an impact.
"Maori and Pacific Islanders eat more fat. But are they eating more fat than 40 years ago? I'm not sure they are."
It's not unusual for Hofman to see nine or 10-year-olds weighing more than 100kg.
Endocrine or hormonal conditions are rare causes of childhood obesity.
However, big mums and dads often produce big offspring. Within weeks, Hofman and his colleagues will embark on a study to determine whether exercise in pregnancy can make a difference to child health.
"Fat mums may well predispose babies to obesity," he says. "They could be getting too much food in-utero.
"We're going to exercise mums in pregnancy and follow up to see whether we can alter things."
For the most part, however, severe obesity in kids comes back to the same root problem - the amount of food consumed versus physical activity.
Hofman is delighted at Trevor Mallard's initiative. When it comes to obesity, a gram of prevention is worth a few kilos of cure.
"Once you're overweight it's really hard to go back," he says. "It's not rocket science. You need 30 minutes to half an hour of hard exercise a day."
Hofman doesn't want to see kids like David subjected to punishing, over-ambitious exercise regimes. Pushy parents and teachers do more harm than good. "It should be fun - they should find things they enjoy doing," he says.
For most kids, Mr Mallard's added daily workouts will be a bonus.