Men who start smoking before their teens have fatter sons, according to new research.
Scientists claim men who were already smoking regularly before the age of 11 had sons with 5-10kg more body fat than their pals by the time they were teenagers.
The effect was not seen in the sons of men who started smoking later, suggesting boys are particularly sensitive to environmental exposures before the start of puberty.
The latest research from the Children of the 90s study could prove that exposure to tobacco smoke at this key age leads to metabolic changes in the next generation.
Senior author of the study, Professor Marcus Pembrey said: “This discovery of trans-generational effects has big implications for research into the current rise in obesity and the evaluation of preventative measures.
“It is no longer acceptable to just study lifestyle factors in one generation.
“We are probably missing a trick with respect to understanding several common diseases of public health concern by ignoring the possible effects of previous generations.”
Researchers questioned 9,886 fathers – 54 per cent (5,376) who were smokers at some time and three per cent (166) reported smoking regularly before the age of 11.
The sons of the men were measures at age 13, 15 and 17, and it emerged the sons of the early smokers had the highest BMIs every time compared with the those who started smoking later or never smoked.
More precisely, whole-boday scans shows these boys had far higher levels of fat mass – ranging from an extra 5kg to 10kg – between ages 13 and 17.
The effect – although present – was not seen to the same degree in daughters.
Scientists also took other factors into account – including genetics and the father’s weight – but none could explain the change.
And in fact, they discovered that fathers who started smoking before 11 tended to have lower BMIs (body mass index) on average.
The research was funded by the UK Medical Research Council.
Professor David Lomas, chair of the MRC’s population and systems medicine board, added: “Population studies have provided a wealth of information about health and disease, including first identifying the link between smoking and cancer more than 60 years ago.
“This research clearly demonstrates that such studies have so much more to give, which is why it’s vital that the future potential of cohorts and the studies they make possible is not jeopardised by the proposed EU data regulations.”
The study was published today in the European Journal of Human Genetics.