A study of identical twins in the US suggests why some people can eat all the fatty foods they want without increasing their blood cholesterol levels, while others have to watch their diets like a hawk. The researchers found that people's genes play a more important role than lifestyle in cholesterol response. The team published their findings in the American Journal of Clinical Nutrition.
The team, led by Paul Williams of the Lawrence Berkeley National Laboratory in California, recruited 28 pairs of identical male twins who led different lifestyles. In each pair, one twin was a keen long distance runner while the other was a comparative couch potato who clocked at least 40 kilometres a week less, if he exercised at all.
For six weeks each twin ate either a high fat-diet, with 40 per cent of its calories from fat, or a low-fat diet, with 20 per cent of its calories from fat. They then switched diets for another six weeks. After each period, the twins' levels of LDL, or 'bad' cholesterol, were tested. The researchers were interested in learning if blood cholesterol changes due to the different diets would be the same in genetically identical twins, despite their lifestyle differences.
Each pair of twins responded in a very similar way to each diet. Some twins had genes that made them sensitive to fat, while others had genes that made them insensitive to fat, no matter how much they exercised. 'If one of the twins could eat a high-fat diet without increasing his bad cholesterol, then so could his brother,' says Williams. 'But if one of the twins' LDL cholesterol shot up when they went on the high-fat diet, his brother's did too.' He added: 'Our experiment shows how important our genes are.'
'This work is very exciting,' Steve Humphries of University College London told the BBC. 'We all know people who put on weight as soon as they look at a cream cake and others who can seem to eat anything and always stay thin.'
The US study showed that genes are important without identifying which ones are involved. Several genes have been associated with cholesterol changes in response to changes in diet, but they cannot account for the large correlation found in the study. Professor Humphries says further research could show which genes make a difference, which may enable scientists to devise special diets for those affected.
Sources and References
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Cholesterol and genes
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Genes 'decide cholesterol levels'
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Genes key to body's cholesterol response: twin study
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