Research by three Canadian universities reveals that in certain circumstances overweight people may be able to blame their size on their genes.
Girls who carry a particular variant of the gene DRD4 (dopamine receptor D4) are predisposed to either increased fat intake, or healthier than average eating habits — which one depends on their socio-economic background.
The study, published in JAMA Pediatrics, finds that certain gene variants make some people more susceptible to the influences of their environment.
The gene is found in a fifth of the population and is associated with obesity, especially in women. The researchers say it is the ‘interplay’ between the gene and girls’ early environment that may determine their eating habits, compared to peers from the same class background. The researchers found that boys who had the same gene variant were not affected in the same way.
Laurette Dubé, the study’s lead researcher, said: ‘We found that among girls raised in poorer families, those with DRD4 repeat 7 had a higher fat intake than other girls from the same socio-economic background. But we also found that girls with exactly the same gene variant who came from wealthier families, compared to these with the same economic conditions, had a lower fat intake.
‘This suggests that it’s not the gene acting by itself, but rather how the gene makes an individual more sensitive to environmental conditions that determines “for better or worse” a child’s preference for fat and consequent obesity as the years pass by.’
The researchers used food diaries kept by the parents of close to 200 young Canadian children with an average age of four. They calculated the percentages of fat, protein and carbohydrates that the children were taking in, and used saliva tests to identify which of the children were carriers of the gene. They then used the family income as a way of measuring the quality of the socio-economic environment in which the children were being raised.
Dr Patricia Silveira, the first author on the study, said: ‘We wondered if the higher fat intake already reported by us in 7-repeat girls could be modified by the social environment — and we showed that it can, as the fat intake will increase or decrease in 7-repeat girls according to their socio-economic status.
‘This is important because we change the focus from the gene (previously “blamed” for the risk for increased fat preference) to the environment, since the effects of the gene will vary according to the conditions in which the child is raised.’
The researchers say that their work demonstrates the importance of moving beyond a ‘one-size-fits-all’ approach to childhood obesity prevention.