Men who start smoking at an early age are more likely to have sons who are overweight, according to a recent study Reuters reported.

British researchers found that men who smoke before the age of 11 raise the risk of obesity in their future sons, Reuters reported. They found that at age 13, 15 and 17, the sons of these early smokers had the highest body mass index scores compared with the sons of men who had started smoking later or who never smoked.

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

For the study, researchers analyzed the detailed lifestyle, genetic and other health data of more than 9,800 fathers. Of the study participants, 5,376, or 54 percent, were smokers at some time and of those, 166, or 3 percent, said they had started smoking regularly before the age of 11, Reuters reported.

Researchers said the findings are part of ongoing work in a larger "Children of the 90s" study. They could indicate that exposure to tobacco smoke before the start of puberty in men may lead to metabolic changes in the next generation.

"This discovery of transgenerational effects has big implications for research into the current rise in obesity and the evaluation of preventative measures," Marcus Pembrey, lead author of the study and a professor of genetics at University College London, is quoted as saying by Reuters.

The effect was not seen to the same degree in daughters, Reuters reported.

The research was prompted in part by suggestions from earlier Swedish studies that "linked how plentiful a paternal ancestor's food supply was in mid childhood with future death rates in grandchildren," Reuters reported.

The findings were published in the European Journal of Human Genetics.