'Obesity gene' works by influencing appetite

A gene associated with obesity works through effects on appetite, according to a study of over 3,000 UK children led by researchers at UCL (University College London) and the Institute of Psychiatry, King's College London, and published in the Journal of Clinical Endocrinology & Metabolism.

The finding helps to unravel the mechanism of the genetic basis of obesity.

Previous studies have demonstrated that the gene, known as FTO, is strongly associated with obesity. However, it was not known whether it affects weight by influencing the amount of food eaten or the amount of calories burnt off. The results of this study strongly suggest that the gene works by modifying appetite, so that the children in the study who had two copies of the higher-risk FTO gene are less likely to have their appetite 'switched off' by eating.

The researchers, led by Professor Jane Wardle, UCL Epidemiology & Public Health, tested whether children carrying the higher risk gene had altered appetite in a sample of 3337 unrelated children aged 8-11 years old. This included parental reports of the children's height, weight and waist circumference and asking parents to complete a specially-designed questionnaire about their children's eating habits, to assess aspects such as their child's enjoyment of food and how easily they became full.

FTO is the first common obesity gene to be identified in Caucasian populations. Previous studies have shown that adults with two copies of the FTO gene are on average 3kg heavier, and individuals with a single copy are on average 1.5kg heavier, than those without the gene.

Lead author of the study, Professor Jane Wardle, UCL Epidemiology & Public Health, said: "While recent research has shown that the FTO gene is strongly linked with children's body weight and food intake, this study tells us more about how the gene could be exerting its effect.

"What we have shown is that children with the 'risky' variants of the gene have weaker satiety responses - meaning they don't just overeat, but they struggle to recognise when they are full. Importantly, the effect of FTO on appetite is the same regardless of the age, sex, socioeconomic background or body mass index of the children.

"It is not simply the case that people who carry the risky variant of this gene automatically become overweight - but they are more susceptible to overeating. This makes them significantly more vulnerable to the modern environment which confronts all of us with large portion sizes and limitless opportunities to eat."

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Notes for Editors

1. For more information, or to interview the researchers quoted, please contact Ruth Metcalfe in the UCL Media Relations Office on tel: +44 (0)20 7679 9739, mobile: +44 (0)7990 675 947, out of hours +44 (0)7917 271 364, e-mail: r.metcalfe@ucl.ac.uk

2. The paper 'Obesity-associated genetic variation in FTO is associated with diminished satiety' (doi:10.1210/jc.2008-0472) has been published online ahead of print in the Journal of Clinical Endocrinology & Metabolism. For copies of the paper, please contact Ruth Metcalfe using the details above.

3. The study was funded by Cancer Research UK, the Medical Research Council and the Wellcome Trust and carried out by researchers at UCL, King's College London and the University of Cambridge.