Children are less likely to be obese if their parents are married, a new study suggests.

According to US scientists, despite the fact that obesity among children is increasing, ‘very little research has been conducted to explore the impact of family structure on this epidemic'.

They decided to look into this further by following the progress of over 10,000 children who came from both traditional and non-traditional homes. Information was collected when the children were nine months old, two years old, four years old and five-to-six years old.

The children had diverse racial, ethnic and socio-economic backgrounds.

The study found that 17% of children from households in which their parents were married were obese, compared to 31% of households in which the parents were simply living together.

Almost one in four children living with a single mother was obese and the same figure applied to children living with a co-habiting step-parent. These results stood even when other factors that influence childhood obesity were taken into account, such as physical activity and diet.

However the scientists from Houston did find two exceptions. Children living with single fathers or in a household where their parent and step-parent were married had an obesity rate of 15%.

"Previous research has shown that single-father households tend to have more socio-economic resources than single-mother households. And since socio-economic status is the single greatest predictor of health, it serves to explain why children in single-father households may be less likely to be obese," they explained.

There was not enough information available to analyse the effect of living with same-sex couples.

The scientists called for more research on this topic.

"For reasons we cannot fully measure, there appears to be something about people who marry and have a child that is fundamentally different than the other groups, and these factors are also linked to children's weight," the team added.

Details of these findings are published in the Journal of Applied Research on Children.