Nearly half the world’s population will be overweight by 2050 if current trends continue, new research suggests.

More than 4 billion people could be overweight by 2050, with 1.5 billion of them obese, if we continue eating large amounts of meat and processed foods, according to a study from the Germany-based Potsdam Institute for Climate Impact Research.

Its authors warn of a looming health and environmental crisis of "mind-blowing magnitude" due to the surge in global food demand, pushing the environment past sustainable levels.

Food production already hoovers up three-quarters of the world’s fresh water and a third of its land, and accounts for up to a third of greenhouse gas emissions.

Meanwhile, the gap between those who don’t have enough to eat and those who have too much will persist, the report says.

The researchers analysed changes in global eating habits since 1965 and looked at factors such as demographic changes, food waste and declining physical activity to predict how food demand might change going forwards.

They found that on a "business as usual" model – a continuation of current trends – 45 percent of the world’s population will likely be overweight by 2050, of whom 16 percent would be obese. 

By 2100, the proportion of the population that is overweight could surge to 56 percent.

That compares to 29 percent of the population who were overweight in 2010, including 9 percent who were obese.

In addition, with both food waste and meat consumption rising, "the environmental impact of our agricultural system will spiral out of control," said Benjamin Bodirsky, lead author of the study published in Nature Scientific Reports. 

"Whether greenhouse gasses, nitrogen pollution or deforestation: we are pushing the limits of our planet – and exceeding them."

Despite veganism becoming increasingly popular in recent years, the authors said that eating habits globally are continuing to move away from plant- and starch-based diets to more "affluent diets" that are high in sugar, fat, meat, and processed foods. On current trends, the demand for animal products like meat and milk will approximately double by 2050.

But despite the expected growth in waistbands, inequality and high levels of food waste mean that half a billion people will still be undernourished by 2050, according to the analysis.

The researchers explained that producing animal-based foods requires more land than producing plant-based foods and releases more greenhouse gas emissions. The consequence is that if meat production increases, there is less plant-based food for other people to eat. People in wealthy countries and communities also throw away too much food.

"There is enough food in the world – the problem is that the poorest people on our planet have simply not the income to purchase it," said co-author Prajal Pradhan. "And in rich countries, people don’t feel the economic and environmental consequences of wasting food."

Rising weights will also burden health systems, leading to higher levels of diabetes, heart disease and cancer. 

Already, the World Health Organization describes obesity as having reached "epidemic proportions", with at least 2.8 million people dying each year as a result of being overweight or obese.

The researchers called for urgent political measures to promote healthy eating, including limits on the marketing of unhealthy foods and a stronger focus on nutrition education in schools.