New research from the UK suggests that physical inactivity in children is the result of obesity and not the other way around, challenging the popular view that getting overweight children to exercise more is the key to preventing the childhood obesity; the researchers maintain the path to childhood obesity is set very early in life, long before children go to school and is linked to early feeding habits.
These are some of the findings of the EarlyBird Diabetes Study, which is based at the Peninsula Medical School in Plymouth and has been following a cohort of city school children for 11 years.
While we all know that overweight children tend to do less exercise, this does not necessarily mean, as many of us might assume, that it is inactivity that leads to obesity, it could be the other way around, and Wilkin and colleagues set out to find some evidence for this and ask the "chicken and egg" question: What came first? Does lack of physical activity precede the changes that lead to fatness in children, or does increasing fatness in children precede changes in physical activity?
By examining the data they had collected over 11 years on over 200 children recruited from 40 Plymouth primary schools, they concluded unequivocally that physical activity had no effect on weight change, but weight change led to less physical activity.
For the study, they examined data on 202 children (25 per cent were overweight or obese, and 53 per cent were boys). The main outcome measures were physical activity and percentage body fat, measured every year.
To measure physical activity, the researchers fitted each child with an Actigraph accelerometer, which they wore for 7 consecutive days once a year. This yielded two measures for analysis: volume and intensity. Thus the researchers could see the total volume of physical activity, and the time the wearer spent doing moderate and vigorous activity.
For the body fat measure the children underwent annual x rays (the method used was dual energy x ray absorptiometry).
When the researchers analysed the results, they found that:
Percentage body fat was predictive of changes in physical activity over the following three years.
Physical activity was not predictive of subsequent changes in percentage body fat over the same follow-up period.
A 10 per cent higher body fat percentage at age 7 predicted a relative decrease in daily moderate and vigorous intensities of physical activity (4 min from 7 to 10 years of age).
But more physical activity at age 7 did not predict a relative decrease in percentage body fat between 7 and 10 years of age.
The researchers suggested that children who become overweight may lack confidence and feel embarassed about how they look and this stops them taking part in sporting activity and exercise.