Obesity in childhood is an epidemic of our times and can be linked to heart, nerve and joint diseases as well as ­diabetes in adulthood.

Moreover, childhood obesity ­measured alongside body mass index was recently linked to an increased risk of premature death by your mid-40s.

Sedentary time in childhood and the teenage years causes increased body fat, especially abdominal.

However, the good news is a study shows that light physical activity (LPA) may completely reverse this. Moderate to vigorous physical activity (MVPA) is not as effective.

The study was conducted in ­collaboration between the universities of Bristol, Exeter, Colorado, US, and Eastern Finland.

It appears that more than 80% of adolescents across the globe don’t meet the World Health Organisation’s recommended average of 60 minutes a day of MVPA.

It’s estimated physical inactivity will have caused 500 million new cases of heart disease, obesity, diabetes or other non-communicable diseases by 2030, costing £21billion annually.

So, how can we tackle it? The study includes 6,059 children aged 11 from the University of Bristol’s Children of the 90s data who were followed up to age 24. Waist-worn accelerometers measured sedentary time, LPA, MVPA, fat mass and skeletal muscle mass at ages 11, 15, and 24.

These children also had their fasting blood samples repeatedly measured for glucose, insulin and cholesterol. In addition, blood pressure, heart rate, smoking status, socio-economic status, and their family history of cardiovascular disease were noted.

The results are salutary. During the 13-year follow-up, sedentary time increased from approximately six hours a day in childhood to nine hours a day in teens. LPA decreased from sixhours a day to three hours a day, while MVPA was relatively stable at around 50 minutes a day. Each one minute spent sedentary led to a 1.3g increase in total body fat.

Both male and female children gained an average of 10kg fat during growth from childhood until young adulthood – 700g-1kg of this was due to being sedentary.

On the other hand, LPA decreased total body fat by 950g to 1.5kg during growth from childhood to young adulthood.

LPA promotes a healthy heart, lowers inflammation and lowers cholesterol levels among children, adolescents, and young adults better than MVPA, and could lower fat mass nearly 10 times more too. Examples of LPA are long walks, household chores, slow dancing, slow swimming and slow cycling, says Dr Andrew Agbaje of Eastern Finland University.

It seems that light exercise goes a long way to prevent obesity. Teachers and parents should try for a goal of three hours per day.