A new study into the global effects of obesity has found that it costs the world economy a massive $2 trillion, that is 2.8 percent of the value of the whole world's economic output.

The report by the McKinsey Global Institute says that obesity does more damage to economies than either drug use or alcohol.

2.1 billion people are either overweight or obese, that is almost 30 percent of the world's population, and two and a half times the amount of undernourished children and adults in the world. The report also suggests that half of world could be overweight or obese by the year 2030.

Ireland upholds the global trend - it is estimated that two out of every three adults, and one in four children are overweight or obese.

In the UK obesity costs the economy more than war and terrorism, the figure is the equivalent of 3 percent of its GDP.

The report cites a number of reasons for the spike in obesity including, "the sedentary nature of modern post-industrial life," as well as the availability of cheap food, and other factors like excessive stress and poor nutritional education.

It also says that there has not been enough research into the topic to formulate a plan to reverse the global trend.

The solution will be dependent on the combination of a number of approaches. The study points out that policies to improve unhealthy lifestyles are highly cost-effective when you compare the cost of implementing them to the current burden that obesity is putting on the global economy.