There has been a lot of speculation as to what is causing the obesity epidemic in today's youth.

Of course, the obvious junk food is a key factor, the lack of exercise too. But one researcher at the University of Leeds, Professor Benton, says there's a link between global trade and the obesity rate and it all centers around one thing.

That thing? Oil.

Professor Benton says recent trade agreements have made it easier to export and import types of cooking oils, which then makes them more common in the foods we eat. These oils are contributing factors to our collective weight problem.

"The poorest anywhere still struggle to get sufficient calories and are underweight, but in our rich countries, poverty often does not stop people being able to eat (and drink) calories, but it does stop them having a nutrient-rich diet," says Professor Benton.

Professor Corinna Hawkes, director of the Center for Food Policy at University of London, agrees with Professor Benton's theory.

"Because it became much easier and cheaper for the processed food industry to import it there was no disincentive for using it," she says.

Professor Hawkes also notes, however, that trade in fruits and vegetables has also increased, making them more readily available. But that doesn't mean they're affordable.

Dr. Joan Cost-Font has a different theory about the obesity rate, however.

"Our food intake is driven towards meeting the needs of a pre-global [socially speaking] world, where people would have to walk to places, and where there would not be as many energy-saving activities as today. Individuals would have closer personal social contacts, and would cook and spend more time on daily chores," he says.

Basically, Dr. Costa-Font believes our ability to shop, travel, and socialize without hardly moving is the leading cause of obesity. The diets we have been eating are targeted towards active, moving people. If we started to eat less in comparison to how much we move, the obesity problem would fix itself.

What do you think the leading cause of obesity is? Let us know.