Fat is a genetic issue
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Whether people are fat or thin is down to a complex mix of environmental factors, such as diet and exercise, and their inherited genetic make-up.
In 2007 a team of Oxford scientists, working with colleagues at the Peninsula Medical School in Exeter, discovered the strongest genetic link yet to overweight and obesity, and hence to consequences of obesity such as type 2 diabetes.
As part of the national Wellcome Trust Case Control Consortium, Professor Mark McCarthy and his colleagues scanned the genomes of 2,000 people with diabetes and a further 3,000 without. They found a variant of a gene called FTO that increased the risk of diabetes by 25 per cent in those with one copy of the variant, and 50 per cent in those with two. Searching for this variant in another 37,000 people, they found that those with two copies of it were on average 3kg heavier than those with no copies, and had a 70 per cent greater chance of being obese.
At the time this study was published no one knew what FTO’s normal role was in the body. By the end of the year another Oxford team, led by Professor Chris Schofield, had discovered that FTO belongs to a family of enzymes that act directly to repair damaged DNA in the cell nucleus. ‘Even though we have yet fully to understand the role played by the FTO gene in obesity, our findings are a source of great excitement’, says Professor McCarthy. ‘By identifying this genetic link, it should be possible to improve our understanding of why some people are more obese, with all the associated implications such as increased risk of diabetes and heart disease.’
The Wellcome Trust Case Control Consortium, which is chaired by Peter Donnelly, Professor of Statistical Science at Oxford, and of which Professor McCarthy’s group is an important part, was named Research Leader of the Year for 2007 in the Scientific American’sSciAm 50 awards.
More recently, working with colleagues across the globe in the so-called GIANT consortium, Prof McCarthy, Dr Cecilia Lindgren and other members of their teams in Oxford have extended the list of genes known to influence individual variation in body mass index and risk of obesity. The total number of such genes is now around 15, each of them having a modest effect on differences in adult weight. These findings have reinforced the view that obesity results from subtle abnormalities of food intake and energy expenditure due to alterations of controlling mechanisms active in a part of the brain called the hypothalamus.
Oxford bestsellers
Dr Ann McPherson, lecturer in general practice, was co-author (with Dr Aidan Macfarlane) of the publishing sensation Diary of a Teenage Health Freak, an amusing and no-nonsense guide to health and safe sex for young people. She has gone on to found the DIPEx website, a directory of people’s experiences of ill health that is not only a valuable resource for newly diagnosed patients but a training tool for doctors.