Children who are severely obese could have just half the average life expectancy if they don’t lose weight in adulthood, according to a study. Research suggests that a severely obese four-year-old boy has a life expectancy of 39, half that of a boy the same age with a healthy weight in the UK. Life expectancies give the further number of years a person can expect to live on average given the age they have attained. The modelling, by Stradoo GmbH, a life sciences consultancy in Munich, used data from 50 existing clinical studies – with more than 10 million participants from across the world – on obesity and obesity-related diseases such as type 2 diabetes and cardiovascular issues. The study measured severe obesity based on BMI Z-scores. These indicate how strongly an individual’s BMI deviates from the norm for their age and sex, with higher values representing higher weight. The variables the study looked at included the age of obesity onset, duration, severity, and a measure of the irreversible risks. For example, a four-year-old boy with an average height of 103cm and a healthy weight of about 16.5kg (2st 8lb) will have a BMI Z-score of 0. By contrast, a boy with the same age and height who is 19.5kg would have a score of 2, while a boy at 22.7kg would be 3.5. A child with a BMI Z-score of 2 would also see their life expectancy reduce from 80 to 65. The research found that early onset of severe obesity in childhood increased the likelihood of developing related co-morbidities such as heart disease and type 2 diabetes. For example, a four-year-old child with severe obesity who doesn’t lose weight had almost a third (27%) chance of developing type 2 diabetes by 25, and a 45% chance by 35. Dr Urs Wiedemann, who presented the study, said the impact of childhood obesity on life expectancy is “profound” and it should be considered a “life-threatening disease”. He said: “While it’s widely accepted that childhood obesity increases the risk of cardiovascular disease and related conditions such as type 2 diabetes, and that it can reduce life expectancy, evidence on the size of the impact is patchy. “A better understanding of the precise magnitude of the long-term consequences and the factors that drive them could help inform prevention policies and approaches to treatment, as well as improve health and lengthen life.” Wiedemann added: “It is clear that childhood obesity should be considered a life-threatening disease. It is vital that treatment isn’t put off until the development of type 2 diabetes, high blood pressure or other ‘warning signs’ but starts early. “Early diagnosis should and can improve quality and length of life.” A quarter of children aged 10 and 11 in England are living with obesity, and worldwide 159 million children are obese.