It may sound strange to bring such a bold message to a meeting where many of the delegates were from developing countries where a lack of food is often the issue. But Oliver disagrees. "For the first time in history, being overweight is killing more people than being under weight," he says. "What is crazy is that even countries that struggle with hunger or famine are beginning to see the exact opposite situation - families in cities eating themselves to death on processed food."
Each year about 5.8 million people die from a disease called diabetes, which gives sufferers problems with blood sugar levels. In 90per cent of those cases, diabetes is caused by being overweight. We used to think of fatness as a Western problem, but that is no longer the case. Statistics from China and India are just as frightening.
"The US isn't even in the top 10 countries," Oliver says. "It's kids in Egypt and Algeria, in Chile and Argentina, pretty much all of South America. China is right behind the US. These are your kids."
Obesity and diet-related illnesses like diabetes, heart disease and some forms of cancer are the world's big killers. "But the crazy thing is, they're also the most preventable, and nothing is being done about it," he says.
Oliver was forthright and says he needs to speak this way because the world faces a health catastrophe, and few people are paying attention.
One of the biggest causes of obesity and diet-related diseases is sugar, he says. "Traditionally we've used sugar as a treat and put it in things like cakes. But these days it is being laced into so many soft drinks, and even savoury foods, that it's like a secret ingredient."
He says modernisation in China reflects the trend of unhealthy eating. "The move from traditional Chinese food to Western-style fast food is an example of "nutrition transition". This is when countries shift from their traditional diets - the sort of food cooked by grandmothers with love and knowledge - to a diet produced in factories or restaurants with lots of fatty, sugary, processed foods."
He says many newly wealthy countries regard pre-packaged food as a symbol of wealth.
"We need to recognise the way kids from England, Australia, China, Kenya and Japan are growing up liking the same football teams, games, music and foods. These 'globo-kids' are all liking the same flavours and being lured by adverts that tell them to get excited by the taste of burgers, fries, fried chicken, soda and low-quality food," he says.
"This globo-food culture is robbing you of your wonderful food and diets and traditions - many of which have been developed over thousands of years."
Oliver is passionate about people knowing how to cook. In many countries, this is a life skill handed down from parents to children, but in very developed societies, like Hong Kong, few people know how to cook. This puts the responsibility for their food in someone else's hands.
"We all have to eat," Oliver says. "Cooking shouldn't be a mystery."
He suggests focusing on local food, trying to cook with natural and local ingredients and having fun. "I've seen people transform their lives in just 10weeks from learning to cook," he says. "I've seen first-hand that it's a whole package: their health, happiness and self-esteem just skyrocket."
Oliver wants children and parents all over the world to make sure that the food they eat is local, healthy and fresh. The benefits, he says, are a bright future.