Some people may have a higher risk of obesity because they are genetically predisposed to overeat or lead a sedentary lifestyle, a leading Cancer Research UK scientist will told conference delegates last week.
Speaking at the charity's second Senior Researchers' Meeting in Harrogate, Yorkshire, Professor Jane Wardle will say certain differences in genetic make-up are likely to influence an individual's attitude to food and physical activity.
The differences could explain why some people find it much harder than others to turn food down when they are not hungry or motivate themselves to exercise.
Obesity is linked to post-menopausal breast cancer and cancers of the womb, gall-bladder and kidney. There is also some evidence that it raises the risk of prostate cancer and cancers of the colon, rectum and pancreas.
Prof Wardle believes understanding the underlying factors behind obesity can help prevent the condition and, in turn, help prevent cancer.
Her team at the Cancer Research UK Health Behaviour Unit are looking into the reasons why children of obese parents have a substantially higher risk of obesity than children of lean parents.
They have compared food and activity preferences in over 400 twin children of overweight parents and normal weight parents. They found that children with overweight parents had a higher preference for fatty-foods and sedentary activities, a lower liking of vegetables and were more likely to overeat.
The team are now looking to distinguish whether these preferences have a genetic basis or are due to environmental factors that are shared within the family.
In the new study they are looking at the same group of children but this time they are comparing the food and activity preferences of twins that are identical with those that are non-identical.
Twins share the same environment so scientists can filter out any environmental influences on a trait and focus on genetic factors.
Identical twins are from the same egg and have 100 per cent of their genes in common while non-identical twins come from two separate eggs and, like any sibling, share on average 50 per cent of the same genes.
So, if a trait is genetically influenced then identical twins will be more similar for that trait than non-identical twins. If, on the other hand, a trait is heavily influenced by shared environmental factors identical and non-identical twins should be equally affected.
The preliminary results of Prof Wardle's study show that identical twins are more alike in their food and activity preferences than non-identical twins – suggesting that there is a genetic basis to these traits.