There may be far more underweight children in Britain than thought, researchers say today, warning that those who are too thin may face a greater threat to their health than those who are too fat.

Despite the widespread and well-documented alarm about the rising obesity epidemic among today’s schoolchildren, being underweight is a serious and under-recognised problem in Britain, scientists claim.

A study of almost 10,000 children between nine and 16 in the East of England found that girls were significantly more likely to be underweight than boys, except among the black community, where boys were more likely to be underweight. One in 17 white children was underweight for their age, according to the classifications used by the International Obesity Taskforce. Among Asians, the rate was one in 11.

The authors of the study, Ayodele Ogunleye and Gavin Sandercock of the University of Essex, say malnutrition is a problem associated with the developing world but remains a major issue in the UK.

Their report states: “The UK is obsessed with overweight and obesity – yet it is now accepted that underweight may contribute a much greater risk to health than overweight. Despite this, our only measurement programme at the National Obesity Observatory does not even mention underweight.”

Speaking to The Independent yesterday, Mr Ogunleye said: “The main risk associated with being underweight is an increased change of osteoporosis, a disease of bones that leads to an increased risk of fractures.

“They are much more likely to have osteoporosis and much lower bone density. Underweight people are likely to be less fit and active, which would also increase their cardiovascular risk. Immune systems, designed to fight diseases and protect the body, are also much weaker in underweight people, which could at the very least lead to them having more illnesses like flu.”

Presenting their findings at the European Congress on Obesity in Liverpool today, they will say it is alarming that half of doctors in England and Wales do not know how to measure underweight in children, with many cases having gone unnoticed.

“Child underweight may be more prevalent than we thought in the UK. There are different reasons… rising food prices, poor diet and fear of being overweight or obese.

“Low muscle mass due to lack of exercise could also be important factors contributing to underweight in England and other developed countries.”

The researchers said future studies should look at the causes of underweight in rich nations and at its prevalence in younger children.

Britain among fattest nations

Britain is among the top 10 fattest nations in the world, with its prospects of prosperity at “high risk” from the burden of an obese population. It is ranked eighth out of 188 countries, according to a new analysis by risk consultants Maplecroft.

Affecting one in four over-15s, obesity costs £21bn in lost productivity each year due to health problems suffered by overweight workers.

Jonathan Owen