Professor John Reilly, of Strathclyde University, has joined an international panel help seek solutions to the causes and problems associated with the condition.
Professor Reilly, of the University's School of Psychological Sciences & Health, is one of only 17 members of the working group reporting to WHO's Director General on science and evidence for ending childhood obesity.
The group will be assessing research and will report back to the director general, Dr Margaret Chan, to the World Health Assembly in 2015.
WHO statistics indicate that at least 40 million children worldwide under the age of five were classed as obese in 2012.
The total is projected to rise to at least 70 million by 2025.