More than 100,000 young scots are now obese, with current weight-measuring methods at risk of underestimating the problem's scaling by up to half, the researchers said.
University of Strathclyde experts have warned that there is a "high number of children and adolescents" whose weight is "apparently healthy" when calculating body mass index (BMI) – but which, despite this, have "a content excessively high body fat ".
Rather than using IMC – based on height and weight – the researchers said using an alternative method to measure obesity would provide a much more accurate picture of the size of the problem.
However, they said the method would also be "more expensive" to use, with more time needed to determine whether young people are healthy or not.
Despite that, Professor John Reilly of Strathclyde School of Psychology and Health said that "it might be worth considering and investing."
Obesity in children is at least twice as prevalent as reported in national surveys and official publications; in fact, more than 100,000 children and young Scottish women will be obese at present
Professor John Reilly, University of Strathclyde
He has recently conducted a study of obesity in Africa, involving 1,500 primary school students from eight separate countries.
This found a significant difference between the level of children defined as obese by BMI (9%) and those classified as obese due to excessive fat as measured by total body water – this method of deuterium dilution resulting in 29% of this group.
Prof. Reilly spoke about how the Active Healthy Kids Global Alliance (AHKGA) report, which evaluates trends in physical activity of children in 49 countries, was published.
The Strathclyde University expert was the Scottish leader for the AHKGA study, which awarded Scotland a D + rating – placing the country in the lower half of the ranking.
Slovenia had the best ranking of any nation with a B, while England received a general C.
Scotland's ranking was, however, better than the US, which received a D, while China received a D.
While Scotland obtained a B for Organized Sports and Physical Activity, it was awarded a F for a high level of sedentary behavior among young people.
Professor Reilly said: "BMI is a simple and effective way to measure obesity in children. It has become widely used in national surveys and public health information, but it is a very crude proxy measure.
The large number of children and adolescents with an apparently healthy BMI for their age have an excessively high fat content.
"Childhood obesity is at least twice as prevalent as reported in national surveys and official publications; in fact, more than 100,000 Scottish children and young people will be obese at present.
"The deuterium dilution measure would be more costly and would take more than BMI – three to four hours compared to 15-20 minutes for BMI – but it would give us a much more accurate picture of the extent of the problem.
"It needs to be properly studied and worth considering and investing."
Prof. Reilly continued, "Our study in Africa has demonstrated the extent to which BMI underestimates the true prevalence of obesity.
"In combination with the Active Children's Healthy report, it suggests that there is no place for childhood obesity anywhere in the world, and urgent action will be needed to prevent and control the problem."
The AHKGA report has discovered modern lifestyles, which imply that people spend more time in front of screens and more and more tasks become automated, have contributed to the global problem of obesity.
Dr. Mark Tremblay, chair of AHKGA and scientist at the CHEO Research Institute in Ottawa, said: "We all have a collective responsibility to address these cultural and social rules – especially screening time – because inactive children are at risk of physical, mental, social and cognitive appearance.
"This generation will face a number of challenges, including the impact of climate change, the rise of globalization and the consequences of rapid technological change.
"They will have to be intentionally physically active to become healthy, resilient adults who can survive and thrive in a changing world."