Waist circumference in young people has risen more steeply over the past 10-20 years than body mass index, particularly in girls. This is a cause for concern because a large waist circumference is linked to a greater risk of disorders such as diabetes and high cholesterol, report researchers in this week's British Medical Journal.
They also say that this means that figures concerning body mass index, the height/weight ratio, has not correctly measured obesity levels in children. The health problem could be even more serious than previously thought.
Researchers obtained data for height, weight, and waist circumference, collected from surveys of young people over the past 10-20 years in Britain. They selected data on 4,560 young people aged 11-16 years for analysis.
Measures of waist circumference increased sharply over the period between surveys, particularly in girls. In 1997, 28 per cent of boys and 38 per cent of girls were defined as overweight (against 9 per cent for both sexes in 1977-87) and 14 per cent of boys and 17 per cent of girls were defined as obese (3 per cent in 1977-87).
Increases in body mass index were smaller and similar in both sexes. In 1997, 21 per cent of boys and 17 per cent of girls were defined as overweight (against 8 per cent and 6 per cent in 1977-87) and 10 per cent of boys and 8 per cent of girls were defined as obese (3 per cent and 2 per cent in 1977-87).
These findings suggest that the accumulation of central body fat has risen more steeply than whole body fatness based on weight and height, say the authors.
Body mass index has therefore systematically underestimated the prevalence of obesity in young people. Increases in waist circumference on current and future illness in young people should be a cause for concern, they conclude.