Feeding a growing planet will be harder because people are getting bigger

As the global human population swells to a projected 9 billion-plus by 2050, the physical size of the average human body will also increase, adding an extra challenge when tackling the spread of global hunger and making projections of future food needs.

Researchers at the Norwegian University of Science and Technology say previous forecasts and calculations typically factored in an average adult whose food needs remain consistent over time. ”These assumptions can lead to errors in assessing how much food we’ll actually need to meet future demand,” the researchers say in a statement. “Based on the discovered trends, feeding 9 billion people in 2050 will require significantly more total calories than feeding the same people today.”

In a new study, published in the journal Sustainability, the scientists analyzed changes in the populations of 186 countries between 1975 and 2014, based on United Nation’s data. Overall, their work showed that people got heavier and taller over time, which changed the number of calories the average person needed to sustain themselves. Between those years, the average adult got 14% heavier, 1.3% taller, and required 6.1% more energy, the study shows. In 1975, the average person consumed 2,465 calories per day. By 2014, that number grew to 2,615.

Across that same time span, the average amount of food people ate increased by 129%. The researchers calculated that shear population growth accounted for about 116 of those percentage points, while increases in weight and height tacked on the extra 15 percentage points. An aging population subtracted about two percentage points because older people tend to eat less.

The researchers found an added layer of complexity when looking at populations from individual nations. According to their work, the average person from Tonga weighs 205 pounds (93kg). Meanwhile, the average Vietnamese citizen weights about 114 pounds (52kg). Also, they found that the average person’s weight in some countries is changing more quickly than in others. The disparities suggest that the food needs for each country have been, and will continue to be different.

Consistently, though, across the planet, countries experienced an increase in food energy demand due to the size of the average person. Of course, the researchers’ 39-year snapshot is just that, a snapshot. The work does not reach further back in history to create a more historical charting of human weight and height changes.

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