Increased sedentary time as a child through adolescence is directly linked to childhood obesity, but new research has found light physical activity may completely reverse the adverse process.

According to recent reports, more than 80 per cent of adolescents across the globe do not meet the World Health Organisation’s (WHO) recommended average of 60 minutes a day of moderate-to-vigorous physical activity.

The new study, published in Nature Communications, shows that moderate-to-vigorous physical activity is up to ten times less effective than light physical activity in decreasing overall gain in fat mass.

“These new findings strongly emphasise that light physical activity may be an unsung hero in preventing fat mass obesity from early life. It is about time the world replaced the mantra of ‘an average of 60 minutes a day of moderate-to-vigorous physical activity’ with ‘at least 3 hours a day of light physical activity’,” said Dr Andrew Agbaje of the University of Exeter.

"Light physical activity appears to be the antidote to the catastrophic effect of sedentary time in the young population," he added.

The study included 6,059 children (53 per cent female) aged 11 years who were followed up until the age of 24. During the 13-year follow-up, sedentary time increased from approximately six hours a day in childhood to nine hours a day in young adulthood.

Light physical activity decreased from six hours a day to three hours a day, while moderate-to-vigorous physical activity was relatively stable at around 50 minutes a day from childhood through young adulthood.

It was observed that each minute spent sedentary was associated with a 1.3-gram increase in total body fat mass.

Both male and female children gained an average of 10kg of fat mass during growth from childhood until young adulthood. However, sedentary time potentially contributed 700 grams to 1kg of fat mass (approximately seven to ten per cent) of the total fat mass gained during growth from childhood until young adulthood.

A 1kg increase in fat has been linked to a 60 per cent higher risk of premature death in a person’s early 50s. Each minute spent in light physical activity during growth from childhood through young adulthood was associated with a 3.6-gram reduction in total body fat mass.

This implies that cumulative light physical activity decreased total body fat mass by 950 grams to 1.5kg during growth from childhood to young adulthood, (approximately 9.5 to 15 per cent decrease in overall gain in fat mass during the 13-year observation period).

Examples of light physical activity are long walks, house chores, slow dancing, slow swimming, and slow bicycling.

 “Our study provides novel information that would be useful in updating future health guidelines and policy statements. Public health experts, health policymakers, health journalists and bloggers, paediatricians, and parents should encourage continued and sustained participation in light physical activity to prevent childhood obesity,” Agbaje said.