By 2025, they estimate there will be 91.2m obese children globally, about 5.4% of all 5-18-year-olds. That compares with 76.2m youngsters in 2010, the baseline year used.
If overweight children are included, the figures are 219m in 2010 but 268.5m by 2025, a percentage rise of all children from 13.9% to 15.8% - or a move from fewer than one in every seven to almost one in six children.
The warning comes in an article in the October issue of Paediatric Obesity by Dr Tim Lobstein and Rachel Jackson-Leach, titled ‘Planning for the worst: estimates of obesity and comorbidities in school-age children in 2025’.
In 2013 the World Health Organisation adopted the health target of halting the rise in diabetes and obesity, using 2010 figures as the baseline.
Dr Lobstein said: “We aimed to assess the scale of the problem facing health planners and service providers.
“The 2025 targets are unlikely to be met, and health service providers will need to plan for a significant increase in obesity-linked comorbidities.”
Comorbidity is when someone suffers from more than one disorder or illness at the same time.
He added: “It would not be unreasonable to assume that around half of the 90m obese school-age children anticipated for 2025 will have one or more of the comorbidities listed.
“If there is no screening service in place, these conditions are likely to remain untreated until they become significantly disabling, and potentially expensive, health problems in adulthood.”
The estimates drawn up by the researchers show that China, with 48.5m, will have the largest number of overweight children with the UK down in 15th place with 3.3m.
In percentage terms, children on south sea islands such as Kiribati (56.9%) and Samoa (46.1%) already have half their youngsters overweight, while the most dramatic increases in the prevalence of overweight children from 2000 to 2013 have been seen in Vietnam (94.8%).