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Many overweight teens don’t realise they’re too heavy

But very few healthy-weight adolescents wrongly believe that they’re overweight

Louis Prime

Thursday, 09 July 2015

Many teenagers who are overweight or obese are failing to recognise the fact, according to new research* from Cancer Research UK. The charity is warning that as a result they might not make lifestyle changes to reduce their weight and their risk of certain cancers. But it also welcomed the fact that only about one in 13 normal-weight adolescents wrongly believed themselves to be overweight.

Almost 5000 normal-weight or overweight/obese adolescents (2,668 boys and 2,311 girls) who had taken part in the Health Survey for England between 2005 and 2012, when aged 13-15 years, answered the question: ‘Given your age and height, would you say that you are about the right weight, too heavy, or too light?’ Researchers then analysed how the teenagers’ perceptions related to their measured body mass index (BMI), and their results are published today in the International Journal of Obesity.

About three-quarters (73%) of participants were of normal weight, 20% were overweight and 7% were obese.

Only 60% of overweight or obese adolescents (53% of boys and 68% of girls) correctly identified themselves as ‘too heavy’ – 39% of this group (47% of boys and 32% of girls) underestimated, identifying themselves as ‘about the right weight’ or even, very rarely, ‘too light’.

Among adolescents with a healthy BMI, overestimation of body size was uncommon. The majority of normal-weight adolescents (83% of boys and 84% of girls) correctly identified themselves as being ‘about the right weight’ and only 7% of normal-weight teens (4% of boys and 11% of girls) identified themselves as ‘too heavy’. About 10% of this group thought they were ‘too light’.

Over the course of the study, between 2005 and 2012, neither BMI standard deviation scores, nor body size estimation, changed significantly.

Cancer Research UK pointed out that being overweight increases the risk of up to 10 different types of cancer, including those of the breast and bowel, and that about 18,000 cancers a year in the UK are estimated to be related to excess weight.

Professor Jane Wardle, from the charity’s Health Behaviour Research Centre at University College London, said: “This study was a cause for celebration and concern. Young people who think they’re overweight when they’re not can sometimes develop devastating eating disorders, so we’re delighted that most of the normal-weight teenagers had a realistic view of their body size.
“But we need to find effective ways of helping too-heavy teenagers slim down and maintain a healthier weight, and it’s vitally important that we find out whether it helps if they are more aware of their weight status. There are no easy answers.”

Julie Sharp, head of health information at Cancer Research UK, added: “It’s important that young people who are too heavy have support to be more active and make healthy changes to their diet – being aware that they are above a healthy weight could be a first step. Making these changes as teenagers could help protect them from cancer as adults.”



* Jackson SE, Johnson F et al. Weight perceptions in a population sample of English adolescents: cause for celebration or concern?  International Journal of Obesity. 9 July 2015; doi: 10.1038/ijo.2015.126.

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