Obese adolescents are increasing their health risks in adulthood, it has been suggested.
Research conducted in the US found that young people are unlikely to shift the weight as they grow up.
Ellen Mason, senior cardiac nurse at the British Heart Foundation, said that while the study did not explore the details behind the levels of obesity, it did "clearly show that obese youngsters are much more likely to become morbidly obese adults".
She added: "Obesity should remain a great cause of concern in the UK because of the associated risk of type 2 diabetes, some cancers and heart and circulatory disease.
"Your heart is just not made to carry so much extra weight over long periods of time."
The study comes as the Organisation for Economic Co-operation and Development warned that obesity levels are rising fast in developing countries, suggesting that the issue is becoming global.