A new study of 188 countries shows that nearly 30% of the global population - or 2.1 billion people - are either overweight or obese. The research has been published in The Lancet medical journal.
It reveals that not a single country has lowered its obesity rate since 1980.
In 2010, it found that overweight and obesity were estimated to cause 3.4 million deaths, or 3·9% of lives lost that year.
It says comparable, up-to-date information about levels and trends is essential to quantify population health effects and to prioritise action.
"We estimate the global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013" it says.
Worldwide, the proportion of adults with a body-mass index (BMI) of 25 kilogrammes per metre squared or greater increased between 1980 and 2013 from 28.8% to 36.9% in men, and from 29.8% to 38.% in women.
It found that the prevalence has increased substantially in children and adolescents in developed countries.
It says 23.8% of boys and 22.6% of girls were overweight or obese last year.
"Because of the established health risks and substantial increases in prevalence, obesity has become a major global health challenge" the report says.
"Not only is obesity increasing, but no national success stories have been reported in the past 33 years. Urgent global action and leadership is needed to help countries to more effectively intervene" it adds.
It found the highest level of obesity was at about age 55 for women with a rate of 14·4%, and about 45 years for men with a rate of 8.1%.
In Ireland, it found that 26.6% of boys under 20 were overweight and obese, while 66.4% of men over the age of 20 fitted into this category.
The number in Irish woman was slightly less, with 26.5% of women under 20 and 50.9% of those over 20 classified as overweight and obese.
The United States was among the top 15 countries in terms of increases in obesity for both men and women; while other countries with large gains include Australia and the UK.
