The findings are published today as part of the BMJ’s Food for Thought 2023 collection examining the science and politics of nutrition. Dr Sarah Maessen and colleagues examined trends in early childhood body mass index (BMI) from five countries.

The researchers found levels obesity and overweight to be steady or decreasing in young children in four high-income countries; Australia, England, Germany and New Zealand. By contrast, in South Africa, an upper middle income country, they found a substantial rise in early childhood overweight, from 19-20% in 1999-2005 to 38-41% in 2012-18, exceeding the rises predicted by the World Health Organisation.

The authors suggest that possible contributing factors to the decrease in early childhood overweight in high income countries include increasing attention on early obesity prevention, changes in infant feeding, investments in early childhood education and childcare, and reduced levels of maternal smoking. The rise in childhood overweight in South Africa may be due to a combination of factors, including low breastfeeding rates, relatively high smoking among younger women, and cultural norms that encourage a chubbier baby

With levels of early childhood overweight still high in high income countries, they recommend several measures to increase the decline in high income countries, which include regulation of marketing of unhealthy food & drinks to young children, greater support for breastfeeding & healthy infant feeding, investment in built environment to facilitate active children, and ensuring that schools and nurseries play a central role in these interventions.

Professor Ken Ong of the MRC Epidemiology Unit, senior author on the BMJ paper, said:

Our new findings provide encouragement that further interventions are likely to continue and hasten the observed declines in early childhood overweight and obesity in wealthier countries, but also highlight the urgent need for more evidence and interventions to halt the alarming rise in childhood overweight and obesity in middle income countries such as South Africa.”

• Sarah Maessen et al. ‘High but decreasing prevalence of overweight in preschool children: encouragement for further action’ BMJ (2023). DOI: 10.1136/bmj-2023-075736