In a study, researchers from various parts of Europe studied diet, lifestyle and obesity and their health effects on children aged 2 to 10 years.
Researchers found that only children have a more than 50 per cent higher risk of obesity compared to their peers with siblings.
The study including 12,700 children 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).
The results were controlled for other influential factors, such as gender, birth weight and parental weight.
Children's Body Mass Index 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," Monica Hunsberger, a researcher at the Sahlgrenska Academy in the University of Gothenburg who contributed to the study, said.
"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," Lauren Lissner, a researcher at the Sahlgrenska Academy said in a statement.
The study was published in the journal Nutrition and Diabetes.
