Environment

This chemical controls whether you would be fat or fatter

Genes interact with obesogens in the environment to make a person fatter 

 
By Vibha Varshney
Last Updated: Saturday 06 July 2019
Photo: Getty Images

In what can be a double whammy for people genetically wired to be obese, genes tend to interact with obesogens in the environment to make the person fatter, according to a study.

Obesogen are chemicals — pesticides, phthalates, medicines — that affect body functions and makes one fat. 

For the study, published in the journal BMJ, researchers from Norway used data from the Nord-Trøndelag Health Study. Out of the total 118,959 people who were part of the study, 67,305 were included in analyses of the association between genetic predisposition and body mass index (BMI).

These people, between the ages of 13 and 80 had their height and weight measured repeatedly between 1963 and 2008.

The result showed that there was an overall increase in obesity through the years. But, in people genetically predisposed to obesity the increase was higher.  Genetic predisposition was identified through the participants' polygenic risk scores.

They were divided into five equal groups (the top five being the most genetically susceptible to higher BMI and the bottom five being the least). Their BMI differed substantially between the highest and lowest groups at each decade.

The difference increased from the 1960s to the 2000s: For example, genetically predisposed 35-year-olds in the 1960s were on average 3.9 kilogram heavier than their genetically protected peer.

But, 35-year-old people genetically predisposed were heavier than 6.8 kg in 2008, said Maria Brandkvist, the lead author of the study, while explaining how environment is a major trigger for obesity.

In addition, both groups gained an extra 7.1 kg due to the obesogenic environment. 

Rising levels of environmental toxins are the major reason behind the increase, the researchers said.

“The obese are often stigmatised for having unhealthy lifestyle choices. Acknowledging the importance of the obesogenic environment and its amplification of our genetic differences, can help destigmatise obesity," Brandkvist stated. 

"Perhaps, it is time to shift our focus away from the individual and towards a healthier society,” Brandkvist added.

The study has implications on policies being developed for combating the obesity epidemic. Controlling the presence of obesogens in the environment would work while the action would also reduce other diseases like cancer. 

Researchers debated for long whether genes or the environment triggered cancer. However, a study carried out on twins in Sweden established that environmental factors cause about twice as many cancers as hereditary factors.

The risk of developing breast cancer, for example, is less than nine per cent if your sister has it, according to the study.

While this was a great respite to those who have a family history of cancer and fear that they, too, would fall victim to it. It also supported more research on the links between the disease and the environment. 

Obesogen include chemicals such as:

  • Monosodium glutamate — popularly called ajinomoto
  • Clozapine, an anti-psychotic drug, Genistein — found in soy products like milk and baby food,
  • Bisphenol A (BPA): Used in plastic and baby bottles and in sealing food cans,
  • Arsenic: Chemical present in rocks and soil, percolates into groundwater and accumulates in crops,
  • Nicotine: An addictive chemical found in tobacco,
  • Dichloro-diphenyltrichloroethane or DDT popular insecticide.

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