The study was conducted under the framework of the European research project Identification and prevention of Dietary and lifestyle-induced health EFfects In Children and infantS (IDEFICS), where researchers from various parts of Europe study diet, lifestyle and obesity and their health effects on children aged 2 to 10 years.
The study shows that only children have a more than 50 percent higher risk of obesity compared to their peers with siblings. The results were controlled for other influential factors, such as gender, birth weight and parental weight.
In the study, the children’s measured BMI was linked to a parental questionnaire that included questions relating to the children’s eating habits, television viewing habits and amount of outdoor play time.
“Our study shows that only children play outside less often, live in households with lower levels of education more often, and are more likely to have televisions in their bedrooms. But even when we take these factors into account, the correlation between siblings and obesity is strong. Indeed, being an only child appears to be a risk factor in and of itself,” says Monica Hunsberger, a researcher at the Sahlgrenska Academy who contributed to the study.
“The fact that only children are more susceptible to obesity may be due to differences in individual family environment and family structure that we were not able to measure in sufficient detail. To better understand the causality, a follow-up study of these families will start next year,” says Lauren Lissner, a researcher at the Sahlgrenska Academy.
Over 22 million children in Europe are estimated to be overweight. The study shows that obesity among children in general is three times more common in southern countries such as Italy, Spain and Cyprus than in Sweden and other northern countries.
The article “Overweight in singletons compared to children with siblings: the IDEFICS study” was published in Nutrition and Diabetes in July.