A new study revealed that over 640 million people globally are considered to be obese, now outnumbering people who are considered to be underweight.

The study, published in the journal The Lancet, analyzed population-based studies that had measured the height and weight of adults aged 18 years and older.

The research used 1,698 population-based data sources, with more than 19.2 million adult participants, consisting of 9.9 million men and 9.3 million women, from 186 countries.

The study applied a Bayesian hierarchical model to the data to estimate trends from 1975 to 2014 in mean body mass Index (BMI).

BMI, as per a Reuters report, is an indication of whether a person is of healthy weight. This index is computed by dividing the weight in kilogram and height in meter squared.

A BMI score of over 30 is considered to be obese, while a score above 40 is considered to be morbidly obese.

The researchers discovered that in the past four decades, the number of obese people in the world has increased from 105 million in 1975 to 641 million in 2014.

The study revealed that obesity is found in 11 percent of men, which went up 8 percent from 1975, and in 15 percent of women, which increased by 9 percent compared to 40 years ago.

Over the past four decades, the average age-corrected male BMI increased from 21.7 to 24.2, while female BMI rose from 22.1 to 24.4. This means that the world's population is gaining an average of 1.5 kilogram each decade.

If this trend continues, researchers predicted that by 2025, 18 percent of men and 21 percent of women will be obese.

According to same Reuters report, despite the prevalence of obesity, low body weight is still an issue in many impoverished countries. In the South Asian region, for instance, almost a quarter of their population is underweight.

As per a US News report, the researchers found out that more than 25 percent of obese males and 20 percent of obese females in the world can be found in the United States.

The research also showed that about 55 million adults in the world are considered to be morbidly obese.