The UK's worsening obesity problem could be solved if children were encouraged to enjoy just 15 minutes of moderate exercise each day.

Researchers at Bristol University have investigated exactly how important exercise is to weight control, amid conflicting reports about the relative merits of diet and physical exertion.

Published in the journal PLoS Medicine, the new report suggests that small additions to a daily exercise routine can bring dramatic long-term benefits. Just 15 minutes a day of moderate exercise lowers a child's chances of being obese by a staggering 50 per cent, the scientists have found.

Encouragingly, the benefits are observed as long as the exercise is at least comparable with a brisk walk, suggesting that parents can help their children enormously simply by walking them to school.

The study examined the activity levels of 5,500 12-year-olds who were asked to wear an Actigraph activity monitor. All participants wore the Actigraph for at least three days and some wore it for a full week. Those taking part in the study also had their body fat measured with the use of an X-ray emission scanner.

Professor Chris Riddoch, who led the research, observed: "This study provides some of the first robust evidence on the link between physical activity and obesity in children.

"We know that diet is important – but what this research tells us is that we mustn't forget about activity. It's been really surprising to us how even small amounts of exercise appear to have dramatic results."

Professor Andy Ness, co-director of the Children of the 90s project, added: "The association between physical activity and obesity we observed was strong. These associations suggest that modest increases in physical activity could lead to important reductions in childhood obesity."

According to a report from Glasgow University, however, children need to engage in at least an hour of exercise each day to address the current obesity crisis. Researchers analysed 545 children who enjoyed 30 minutes of exercise three times a week, but this was found to be insufficient.

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