A study published in the Bulletin of the World Health Organization (WHO) says that more than a third of the world's population - 37% of men and 38% of women - is overweight.
Between 1980 and 2013, the proportion of adults globally who were overweight -- those with a body mass index (BMI) of 25 kg/m2 or more -- increased from 28.8% to 36.9% in men, and from 29.8% to 38% in women, the results said.
A person with a BMI of 30 or more is considered obese. The researchers found that the number of overweight and obese people is increasing globally in step with increases in consumption of energy dense or high-calorie foods such as processed foods.
"We know that other factors have also changed over these decades such as increased urbanization, car dependence and sedentary occupations, which are also contributing to the global obesity epidemic," said lead author Stefanie Vandevijvere, senior research fellow in global health and food policy at the University of Auckland, New Zealand.
"However, the study shows that oversupply of available calories is a likely driver of overconsumption of those calories and can readily explain the weight gain seen in most countries," she said.
The study analyzed increases in the food energy supply and obesity in 69 countries (24 high, 27 middle and 18 low-income) and found that both body weight and food energy supply had increased in 56 of them between 1971 and 2010.
In 45 countries, the increase in available calories was enough or more than enough to explain the concurrent increase in body weight, the study said.
"Much of the increase in available calories over the decades has come from ultra-processed food products, which are highly palatable, relatively inexpensive and widely advertised, making overconsumption of calories very easy," Vandevijvere said.
The study is important because it provides more evidence that governments need to implement policies to make the food supply healthier and, in turn, reduce obesity, which is a risk factor for many health problems, including diabetes, heart disease, stroke and some cancers.