Food habits and lack of exercise also play a big part in getting obese.

A study suggests that obesity is more linked to lack of exercise and considerable shift in diet to unhealthy pattern and not just genes.

The study says genes do play a role but the excess kilos don’t just depend on them. Food habits and exercise also do play a part in getting obese.

For people genetically predisposed to a wider girth, these unhealthy lifestyles compounded the problem, resulting in an even higher rate of weight gain, researchers reported in The BMJ, a peer-reviewed medical journal.

The standard measure for obesity, the Body-Mass Index (BMI), is calculated on the basis of weight and height.

A BMI of 25 up to 30 means that one is overweight. Thirty and above corresponds to obesity, a major risk factor for heart attacks, stroke, diabetes and some cancers.

About four percent of adults in the mid-1970s had a BMI of 30 or higher. By 2016, that share had risen to 13 percent (11 for men and 15 for women), according to the World Health Organization.

'Obesogenic' environment

Half of the people monitored were divided into five groups depending on their genetic susceptibility to obesity.

Comparing the two groups at the extremes, the researchers found, for example, that 35-year-old men with genetic variants known to favour weight gain were already heavier in the mid-1960s than men the same age without those fat-inducing genes.

Four decades later -- even as obesity rates increased across the board -- that gap nearly doubled.

Agence France-Presse