More than 100,000 young Scots are now fat, and current methods of measuring weight are at risk of underestimating the extent of the problem by half, the researchers said.
Experts from the University of Strathclyde warn that there is a "large number of children and young people" whose weight is "apparently healthy" when their body mass index (BMI) is calculated – but which is still "excessive fat content".
Instead of using BMI – based on height and weight – researchers said using an alternative method for measuring obesity would give a "much more accurate picture of the extent of the problem".
However, they said that the method would also be "more expensive" to use, so more time is needed to find out if the young are healthy or not.
Nevertheless, Professor John Reilly Strathclyden's School of Psychological Sciences and Health said that "it could be worth considering and investing."
Childhood obesity is at least twice as common as reported in national studies and official publications; In fact, more than 100,000 Scottish children and adolescents suffer from obesity at this time
Professor John Reilly, University of Strathclyde
He recently led a study of obesity in Africa, involving 1,500 primary school students in eight different countries.
This found a significant difference between the BMI (9%) and the total number of obese children in the measurement of total water – the deuterium dilution method that led to 29% of this group.
Prof Reilly spoke of a report by the Active Global Healthy Child (AHKGA) report assessing the development of childhood physical activity in 49 countries.
The Strathclyde University Specialist was Scotland's AHKGA research, which gave Scotland a D + rating – to invest in the lowest half of the country.
Slovenia had the best ranking of all countries in the category B, while England was given a C size.
However, Scotland's ranking was better than the US that got D, while China was awarded D.
Although Scotland made B for organized sport and physical activity, it got F's high-level seating behavior among young people.
Professor Reilly said: "BMI is a simple and cost-effective way to measure obesity in children, which has become more common in national and public health data, but is a very good resource.
"A large number of children and adolescents who are obviously healthy for their BMI age have excessive fat content.
"Childhood obesity is at least twice as high as in national studies and official publications; In fact, more than 100,000 Scottish children and adolescents suffer from obesity at this time.
"The deuterium dilution measure would be more expensive and last longer than BMI – from three to four hours in the 15 to 20 minute BMI – but it would give us a much more accurate picture of the extent of the problem.
"It has to be properly investigated and can be valuable and investing."
Prof. Reilly continued: "An African study showed the extent to which BMI underestimates the actual prevalence of obesity.
"Together with the Active Healthy Kids report, it suggests that there is no more room for dissatisfaction with childhood obesity anywhere in the world, urgent measures are needed to prevent and control the problem."
The AHKGA report found that modern lifestyles, where people spend more and more time in front of actors, and more and more tasks automated, have contributed to the global problem of obesity.
Dr. Mark Tremblay, AHKGA Chair and Senior Researcher at the CHEO Institute of Ottawa, said: "We all have a common responsibility to address these cultural and social norms, especially the time of the screen, because active children are at risk of harmful physical, psychological, social and cognitive health problems .
"This generation will face different challenges such as the effects of climate change, the increasing globalization and the consequences of rapid technological change.
"They must be physically active in order to grow into a healthy, resilient adult who can survive and succeed in a changing world."