Men who start smoking before their teens can expect to have fatter sons, according to new research.

According to Reuters, new research suggests that men who started smoking tobacco before the age of 11 have an elevated risk of having an overweight son, with five to 10kg more body fat than average.

"This discovery of transgenerational effects has big implications for research into the current rise in obesity and the evaluation of preventative measures," said Marcus Pembrey, a professor of genetics at University College London, according to Reuters." It is no longer acceptable to just study lifestyle factors in one generation."

The latest research from the Children of the 90s study at the University of Bristol could indicate that lifestyle factors during an individual's' "childhood can affect the health of their future offspring. Researchers believe that the toxic chemicals within tobacco smoke can possibly cause changes to inherited DNA that can trigger a "metabolic reaction in the boys."

Researchers looked at 9,886 fathers and analyzed their lifestyle, genetic and other health data. The study concluded that fifty-four percent, or 5,376, of these men were smokers and three percent, or 166, of them admitted to smoking before the age of 11.

Sons of those that began smoking before the age of 11 were more likely to have a higher Body Mass Index (BMI) at the ages of 13, 15, and 17, compared to the sons of men who never smoked or began smoking at a later age. Ten kg is equivalent to about 22 pounds.

"These boys had markedly higher levels of fat mass - ranging from an extra five kilograms (kg) to 10kg between ages 13 and 17," the study said.

The effect was not seen in the sons of men who started smoking later nor in father's that had daughters.

"[The findings] may potentially provide new insights into factors that may influence development of obesity in childhood," said Graham Burdge, an expert in human nutrition at the University of Southampton, according to Reuters. "However, the findings only show associations and cannot be interpreted as indicating that paternal smoking at an early age causes obesity in their sons."

According to the World Health Organization, almost one billion men smoke in both developed countries and developing countries. Smoking rates in Britain and some other parts of Europe are on the decline.

The new study is published in the European Journal of Human Genetics.