Malnutrition is the world's worst child health crisis and climate change will only make things more severe, according to Microsoft-co-founder turned philanthropist Bill Gates.

Between now and 2050, 40 million more children will have stunted growth and 28 million more will suffer from wasting, the most extreme and irreversible forms of malnutrition, as a result of climate change, the Bill & Melinda Gates Foundation said in a report on Tuesday.

“Unless you get the right food, broadly, both in utero and in your early years, you can never catch up,” Gates told Reuters in an online interview last week, referring to a child’s physical and mental capacity, both of which are held back by a lack of good nutrition. Children without enough of the right food are also more vulnerable to diseases like measles and malaria, and early death.

"Around 90% of the negative effect of climate change works through the food system. Where you have years where your crops basically fail because of drought or too much rain," he said.

Gates was speaking ahead of the publication of the Bill and Melinda Gates Foundation's annual Goalkeepers report, which tracks progress on the United Nations Sustainable Development Goals (SDGs), around reducing poverty and improving health. The report includes the projections above.

In 2023, the World Health Organization estimated that 148 million children experienced stunting and 45 million experienced wasting.

Gates called for more funding for nutrition, particularly through a new platform led by UNICEF aiming to co-ordinate donor financing, the Child Nutrition Fund, as well as more research. But he said the money should not be taken away from other proven initiatives, like routine childhood vaccinations, for this purpose.

“(Nutrition) was under-researched ... it's eye-opening how important this is,” he added, saying initiatives like food fortification or improving access to prenatal multi-vitamins could be as effective as some vaccines in improving child health in the world’s poorest countries.

The Gates Foundation said in January it plans to spend more on global health this year than ever before - $6.8 billion – as wider funding efforts stall.