The problem with childhood obesity in Scotland may be greater than expected, as researchers argue that weight estimates may be inaccurate.
Strathclyde University researchers have said that many young people who look healthy have "high body fat".
They also warn that the current method of weight measurement – the Body Mass Index (BMI) – risks to underestimate the scale of the problem by more than half.
Researchers estimate that more than 100,000 young Scots are already overweight.
They said that using an alternative method of measuring obesity would give a much more accurate picture of the scale of the problem.
But they said the method would be "more expensive" and would take longer.
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Professor John Riley of Strathclyde School of Psychological Science and Health said that "it may be worth investing and attention."
He added: "BMI is a clear and cost-effective way to measure obesity in children, and it is widely used in national research and public health information, but it is a very crude proxy.
"A large number of children and adolescents with apparently healthy BMI for their age have extremely high body fat.
"Obesity in childhood is at least twice as prevalent as it is reported in national surveys and official publications – in fact, more than 100,000 Scottish children and young people are currently obese.
"The measure of dilution of deuterium would be more expensive and it would take more than BMI – three to four hours compared to 15-20 minutes for BMI – but that would give us a much more accurate picture of the scale of the problem.
"It needs to be explored properly and can be worth considering and investing."
"Emergency measures needed"
Prof. Riley has recently conducted a study of obesity in Africa involving 1,500 primary students in eight separate countries.
This establishes a significant difference between the level of children identified as obese from BMI (9%) and those classified as obese with excessive thickness measured by total body water.
The second method, called dilution of deuterium, is 29% of children classified as obese.
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Prof. Riley talks as AHKGA report, which assesses the trends in child physical activity in 49 countries.
University expert at Strathclyde is the head of the Scottish AHKGA study project, which gave Scotland a D + rating that puts the country in the bottom half of the ranking.
Prof. Riley continued, "Our study in Africa has shown to what extent BMI underestimates the true spread of obesity.
"In conjunction with the report" Active Healthy Children, "it shows that there is no room for complacency about childhood obesity around the world, urgent measures will be needed to prevent and control the problem."
How does Scotland compare?
Slovenia had the best ranking of all nations with B, and England received a total of C.
Scotland's ranking, however, was better than the US, which received D, and China received D-.
While Scotland scored B for organized sport and physical activity, she received F for high levels of sedentary behavior among youngsters.
The AHGA report has found that modern lifestyles, including screen time and more and more automated tasks, have contributed to the global obesity problem.
Dr. Mark Tremblay, President of AHKGA and senior scientist at the CHEO Research Institute in Ottawa, said: "We all have a collective responsibility to deal with these cultural and social norms – especially with time on the screen – because inactive children are exposed to risk of unwanted physical, mental, social and cognitive health problems.
"This generation will face a number of challenges, including the impacts of climate change, increasing globalization and the consequences of rapid technological change.
"They have to be deliberately physically active to become healthy, sustainable adults who can survive and thrive in the changing world."