Plain english summary

In recent years children have become less active (take less exercise), more sedentary and eat less fruit and vegetables than children did in the past. These changes affect normal healthy growth and development in children and mean that children are now more likely to be overweight or obese. Getting all children to exercise more and eat better diets would be likely to reduce the number of children who are overweight and would have other health benefits. Children would be likely to have healthier hearts, lungs, bones and muscles. We also know that children who have healthy levels of activity and intake of fruit and vegetables are more likely to have healthy levels of these behaviours as adult, which means that the health benefits of getting children to be more active, less sedentary and eat more fruit and vegetables last throughout life.

A number of studies, mostly conducted in the US, have shown that school-based interventions where children are taught about healthy diets and physical activity are effective in improving behaviours in childhood. However, there have been problems with these studies. First, they have not measured long-term effects beyond the end of the intervention. This is important because part of the beneficial effect with respect to children receiving the extra lessons could have been simply because many of these lessons were 'PE' and therefore to some extent the children were compelled to be more active. We think it is important to know whether school-based interventions have a lasting effect. Second, previous studies have relied on children or their parents reporting how active and how much TV the children watched on an average day, rather than objectively measuring this. This might have exaggerated the apparent beneficial effect of these school-based interventions. It is possible to objectively assess activity and sedentary behaviour with small devices that children wear around their waists and we have shown it is possible to do this in 9-10 year old children. Lastly, to date only three studies have been conducted in the UK. These were conducted some time ago and had important methodological weaknesses. It is not clear that interventions that are effective in the US or other counties will be here.

We have been working for three years with teachers, parents and children in primary schools (35 schools and over 1000 children age 9-10) to develop an intervention that includes teaching lessons about healthy diet and exercise and involving parents in homework activities that reinforce these messages. The results of this work show that it is possible to do this intervention in the UK and teachers, parents and children like it. The results suggest that in the short-term the intervention does increase physical activity, reduce sedentary behaviour and increase fruit and vegetable consumption.

We would now like to do a large study where we would randomly select 30 schools (750 children) to have this intervention and 30 not to have the intervention immediately (but to have it at the end of the study). We will examine how effective this intervention is in increasing physical activity, reducing sedentary behaviour and increasing fruit and vegetable consumption in 9-10 year old children immediately after it is completed and also 1 year later (to test whether there are lasting effects). We will use objective measurements of physical activity and sedentary behaviour by asking the children to wear accelerometers for 5-days, which will detail amounts and intensities of the movements the children undertake. The study will provide important information about how to improve children’s health in a cost-effective way via schools.