Exercise 'does not prevent obesity in pre-school children'

Exercise has little impact on obesity rates in pre-school children, a study published today found.

Three 30-minute sessions of activity a week and increasing exercise at home has little effect on body mass index (BMI), according to research published online in the British Medical Journal . But experts from the University of Glasgow said there were improvements to movement skills which could give children the confidence to continue exercising and have long-term health benefits.

The trial involved 545 pre-school children from 36 nurseries. The children, with an average age of 4.2, took part in a nursery-based active play programme of three 30-minute sessions a week for 24 weeks. Parents were also given guidance on increasing physical play at home but there was no change to diet. BMI readings were taken after six months and a year.

The children were also assessed for movement skills and to establish if the increased activity had led to a reduction in their sedentary behaviour. The authors concluded that increasing activity had little impact on BMI. "Physical activity can significantly improve motor skills but did not reduce body mass index in young children.

"There was evidence of a benefit of the intervention for movement skills. This might foster an increase in activity in future by increasing confidence or ability in children to carry out physical activity, and may have direct effects on body fat in the long term."

The authors called for changes to the environment outside the home that could help increase activity and said that changes to diet may also be needed.

Tam Fry of the Child Growth Foundation welcomed aspects of the study but criticised its scope. "Half an hour of physical activity should be a daily event for pre-school children. To measure its true impact on BMI the study should have required seven sessions a week - not three."

Dr Mike Knapton of the British Heart Foundation said it was "crucial" to encourage good exercise habits in young children. "Children get less active as they get older so it's vital that youngsters get regular physical activity to lay the foundations for good health as they grow up."