Britain's "national obsession" with obesity is creating a potential public-health crisis by neglecting the growing numbers of unfit schoolchildren, experts are warning. Declining child-fitness levels are being overshadowed by obesity targets, leaving schoolchildren at increased risk of cancer, heart disease, stroke and diabetes, according to researchers.
By the age of 15, children are five times more likely to be unfit than obese, according to the first study to compare rates of obesity and fitness among British schoolchildren.
The alarming figures are fuelling calls for fitness tests in schools to identify children at risk.
Professor Sir Liam Donaldson, former Chief Medical Officer, last night warned: "There is a risk that tunnel vision on childhood obesity will mean cardiovascular fitness is ignored. Being fat shortens life but so does being unfit and of normal weight."
The study sampled 8,500 pupils, aged 10 to 16, from 24 schools in the East of England. The children involved were measured for their body mass index (BMI) and made to do 20-metre shuttle runs to test cardiorespiratory fitness.
Researchers found that while more than one in 10 (11 per cent) of 11- to 16-year-olds are obese, a far higher proportion – more than one in five (20-plus per cent) – are unfit. One in four obese children has good physical fitness, and one in five children with normal BMI has a low fitness level.
And while levels of obesity fell from 13 per cent of 10-year-olds to 8 per cent of 15-year-olds, the proportion of unfit children soared from 15 per cent of 10-year-olds to more than 40 per cent of those aged 15, according to the study.
"Our data on older children show a drop in obesity levels throughout secondary-school children... Unfortunately the results show that poor fitness, which is a much better indicator of overall health than BMI, increases dramatically," said Dr Gavin Sandercock, of the University of Essex, who led the research. He added: "The national obsession with children's weight... may be leading us away from a much bigger problem – their poor levels of fitness."
The findings, presented at the annual conference of the British Association of Sports and Exercise Sciences (Bases) this month, will appear in the December edition of the Journal of Sports Sciences.
"The fact that nearly half of Year 11 pupils are unfit by the time they leave school is frightening, as this is likely to get worse when they stop doing PE – it is creating a potential public-health time bomb," warned Dr Sandercock.
Children with a normal BMI who are unfit face greater health risks than those who are overweight but fit, say experts. Yet schoolchildren are only measured for their BMI, and there is no systematic evaluation of their fitness.
Professor Mitch Blair, officer for health promotion at the Royal College of Paediatrics and Child Health, said there was no time to waste: "As this important study suggests, we need to rethink how we use values such as BMI for predicting long-term health .... Being thin is not necessarily the same as being fit, and we need to re-examine how we measure children's fitness, for example by piloting a standardised measurement strategy in schools."
Sir Liam Donaldson, chair of health policy at Imperial College London, said: "I strongly urge the Government to pilot test comprehensive fitness testing in schools" – repeating a recommendation he made in 2009 which the Government has yet to act upon.
The study comes amid mounting concern over the health of Britain's children. Nearly half (49 per cent) of seven-year-olds fail to meet the Government's minimum recommended level of one hour of exercise a day, according to research published in the medical journal BMJ Open last month.
The health risks faced by unfit children are part of a wider problem. Last week the World Heart Federation warned that most Britons (67 per cent) fail to manage even 30 minutes of brisk walking a day – putting themselves at greater risk of ill health.
Dr Kathryn Taubert, the federation's chief science officer, said: "Paying attention to how much we walk should be as simple as watching what we eat. By reaching the recommended minimum 30 minutes of moderate exercise, which includes brisk walking, at least five days a week, many premature deaths can be prevented."
And Dr Keith Tolfrey, of the British Association of Sport and Exercise Sciences, said: "Low fitness , particularly cardiorespiratory fitness, is equally, if not more, important than obesity in young people."
In a statement, a government spokesperson said: "We know that too many children are overweight so it is vital that children exercise regularly. All schools should ensure that pupils have a strong understanding of personal fitness and are free to decide how to judge this as part of their PE lessons."
Primary schools are being given £300m of ring-fenced funding over the next two years to improve PE and sport and help all pupils to develop healthy, active lifestyles, they added.
Recognising that simply slimming fat children through healthy eating is not the answer, the Government recently launched a Change4Life campaign in a bid to encourage people to get more active.
Professor Blair, a consultant paediatrician and expert on child public health , said that healthy eating and exercise are "essential life skills" and "need to be seen as important as reading, writing and maths.
"Until we get this right, the growing issue of obesity and decrease in fitness is only going to get worse."