Obesity is a global pandemic, affecting millions of people in North America alone. It has been associated with medical conditions, such as cardiovascular complications and type 2 diabetes.

A recent study published in JAMA Pediatrics suggests that diet may not be the primary cause of obesity. Rather, the presence of a certain gene in women may also be a contributing factor.

Researchers at McGill University recently discovered that the fat intake of women is influenced by a gene called the DRD4 VNTR repeat 7. Although this gene alone does not cause women to become obese, the way that the gene affects the fat intake of the body depends on the environment that the carrier of the gene grew up in.

In particular, the presence of the DRD4 repeat 7 gene, present in approximately 20 per cent of the population, is informed by the carrier’s socioeconomic background. Women who carry the gene will have increased or healthier than average fat intake, if they grew up in a poorer or richer household, respectively. Lead author Laurette Dubê believes that the higher fat intake is due to the carrier’s food choices, rather than due to an underlying metabolic mechanism.

The study focused on 200 Canadian children, aged four, from Montreal, Quebec and Hamilton, Ontario. The researchers calculated the percentages of fat, protein, and carbohydrates the children had consumed based on diaries kept by their parents, while saliva tests were used to determine which children were carriers of the DRD4 repeat 7 gene. The quality of their socio-economic environment was estimated using family income.

“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,” said Laurette Dubé.

Conversely, wealthier girls with the same gene variant had a lower fat intake than other girls in the same economic conditions. “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 […] a child’s preference for fat and consequent obesity as the years pass by.”

The study confirms that DRD4 repeat 7 belongs to a larger class of plasticity genes, which increase or decrease the risk of certain medical conditions depending on an individual’s environment. The study confirmed that DRD4 repeat 7 was indeed a plasticity gene. These results provide a clearer explanation of the underlying causes of diseases like obesity, changing the  focus from the gene to the environment.

Boys with the DRD4 repeat 7 gene were not affected. Perhaps it is because girls need to be prepared to gain more weight to reproduce. Or perhaps it is too early to see the effects of the gene in boys at the tender age of four. Boys and girls gain weight at different stages in this age.

The outcomes of this study have further advanced our knowledge of obesity. Rather than merely blaming genetics, it is now evident that the environment in which one is raised plays a significant role on the development of obesity. It is therefore necessary to focus on both genetic and environmental factors to adequately prevent the pandemic.