Children who grow up without siblings have a more than 50 percent higher risk of being overweight or obese than children with siblings, according to a new study.

This finding is based on the study of 12,700 children in eight European countries, including Sweden.

The University of Gothenburg, Sweden, was one of the participating universities in the study.

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 9 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 playtime.

"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 bedroom," said Monica Hunsberger, a researcher at the Sahlgrenska Academy, University of Gothenburg, who contributed to the study.

"But even when we take these factors into account, the correlation between singleton status and overweight is strong. Being an only child appears to be a risk factor for overweight independent of the factors we thought might explain the difference," she added.

Lauren Lissner, a researcher at the Sahlgrenska Academy, University of Gothenburg continued, "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."

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.