It’s world obesity day and it’s come with a pretty grim warning. 

In 8 years from now, obesity will cost the world’s health systems $1.2 trillion. 

$1.2 trillion. Why? Because in eight years a third of the world will be obese. 

The World Obesity Federation has cost in, not just cancer, diabetes and heart disease in that $1.2 trillion, but also the cost of hip, knee and back complications associated with carrying extra weight. 

Here? Well the latest figures we have show that over quarter of a million school children are obese. 

And when you look at the adult statistics, a third of men are obese, and just over a third of women.  The Americans are the worst but we’re just behind them. 

It’s not just that our waistlines are growing, it’s the ‘number’ of our waistlines that are growing. More and more of us are medically obese.

And how do you measure obesity? Well, that's a difficult one. Many use BMI, the body mass index, but that doesn't take into account ethnicity and other factors. If you use BMI, that means your average all black forward is technically obese and so is Valerie Adams and that, of course, not the case.  Kate, my producer is a giant. She's very tall. She's 5.11 or around 180cm and around 78 kgs, and she's a string bean. But based on the BMI she's overweight. 

America's national heart, lung and blood institute uses a fairly non-scientific method of measuring your risk of obesity-related disease. In men, it's when your waist is greater than 102cm or 40 inches, and in women, it's 88cm or 35 inches. But the head of diabetes in the UK once told me that the simplest way to determine if you're obese or not, is to look at your waist. He said if it's bigger than your hips, then technically you’re obese. 

But irrespective of how you measure it, the fact remains, we're getting bigger, not smaller. And every economy in the world is facing a very steep rise in costs and a rise the world obesity federation says it will bankrupt economies. 

What do we do? The federation says government's need to intervene. 

They support a sugar tax, they also believe bariatric surgery is effective, that's when you have a gastric band, or your stomach stapled. They say it's safe and incredibly effective and if the world's health systems upped the number of operations they performed each year, it would dramatically reduce the level of obesity. And it's relatively cheap too. About a third of the cost of a knee replacement.

Surgeons and experts in the UK have urged the NHS to dramatically increase the number of stomach-shrinking operations they carry out each year.  Professor Francesco Rubino, the Head of Meabolic and Bariatric Surgery at Kings College in London, says we have to remove the stigma associated with obesity. Remove the judgement. Don't blame obese people. Instead, he says, we should invest in them. Offer bariatric surgery and it will be offset by the economic and health benefits in future. 

Our health system is under huge strain already. If we don't intervene, our obesity epidemic could cripple it. 

So is gastric banding the answer? It sounds extreme, doesn't it? But think about it. Upping the number of gastric band surgeries would cost taxpayers significantly less than what it would to treat all the health implications down the line.