While school is an important setting for supporting healthy lifestyles, the researchers say wider influences - for example from families, local communities, and the food industry - may have a greater effect than any school run intervention.
In the UK, around a quarter of children are overweight when they start school at age 4 or 5 years - and the proportion of very overweight children doubles during the subsequent six years (from around 9% to 19%), highlighting this period as critical for preventive action.
Previous reviews of the evidence suggested that school based interventions might be effective in reducing the proportion of overweight children, but study weaknesses have prevented researchers from making any firm recommendations.
So a team of researchers, led by Professor Peymane Adab at the University of Birmingham’s Institute of Applied Health Research, set out to assess the effectiveness of a lifestyle and healthy eating programme (West Midlands ActiVe lifestyle and healthy Eating in School children or WAVES) compared with usual practice, in preventing childhood obesity.
WAVES is a 12-month school delivered intervention focusing on healthy eating and physical activity among primary school children. The results are based on data from around 1,400 6 and 7 year olds at 54 randomly selected state run primary schools in the West Midlands, monitored over a two and a half year period.
At the start of the trial, height and weight was recorded for each child, along with other measurements relating to body fat, diet and physical activity levels.
The programme included daily additional physical activity opportunities in schools, a physical activity and healthy eating programme in conjunction with local sporting heroes, regular information to parents about local physical activity opportunities, and workshops on healthy cooking for families at schools.
The researchers found no significant difference in weight status and no meaningful effect on body fat measurements, diet or physical activity levels at 15 and 30 months in children taking part in the programme, compared with those not taking part.
The researchers point to some limitations, such as possible imbalances between the groups at the start of the trial, but say strengths include the large number of schools involved, and lengthy follow-up.
They suggest that “nudge” interventions - for example using financial incentives to prompt healthier behaviour - merit further investigation, but they conclude that school-based motivational, educational approaches “are unlikely to halt the childhood obesity epidemic”.