The study, published in Public Health Nutrition and covering 140 rural villages in nine provinces, found that some 61m young people faced a dangerous nutritional imbalance.
Led by Nan Zhang, the Manchester University researchers analysed the nutritional intake of 975 children, finding a particular risk to boys who were left behind. Many of them were left in the care of grandparents or a single parent while a mother or father sought work away from home.
Zhang said the greater financial security migrant parents might bring to a family could often be at the expense of child nutrition.
“The Chinese government needs to recognise this growing problem among rural communities, and this research provides some evidence to target health policies on encouraging a balanced diet,” said Zhang.
The study found that “left-behind” boys in particular consumed more fat and less protein than those from complete families, leaving them at increased risk of obesity and stunted growth.
This had important policy implications in a country where “son preferences” were prominent.
Although the findings don’t provide reasons for this change in diet, the researchers speculate that mothers who moved away from home generally earned less.
These lower earnings would act in combination with grandparents’ poorer dietary knowledge or willingness to spend more on food, said Zhang, who has also released a paper exploring the intergenerational differences in beliefs about healthy eating for left-behind children among grandparents and parents in the journal Appetite.
The fact that the prices of protein-based foods including eggs and meat have increased faster than many households’ incomes could also have an impact. Nutrition doesn’t necessarily improve even if money is sent home from one or both parents, Zhang said.
“The process of parental migration is complex and the reasons for problems in boys’ nutrition are not straightforward. However we can see that both parents and grandparents in rural areas need to be educated about good diet,” she said.
“Because raising children can fall on all members of the family, good care-giving practices need to become more widespread.”