Study: Men who started smoking as boys could be more likely to father obese sons

The study found that the sons of the men who started smoking before 11 were consistently fatter than the sons of men who started smoking later (Getty Images)

Men who started to smoke before the age of 11 are more likely to have overweight teenage boys compared to men started smoking later in life or who have never smoked at all, a study has found.

Scientists said that the teenage sons of fathers who started smoking when they were themselves children were on average significantly fatter than other teenage boys, which indicates that tobacco smoke can lead to metabolic changes in the next generation passed on through the sperm.

The research, funded by the Medical Research Council, was carried out on nearly 10,000 fathers who enrolled in the Avon Longitudinal Study of Parents and Children. However, of the 5,376 men who said they were smokers at some time in their lives, only 166 reported starting before the age of 11.

Nevertheless, scientists led by Professor Marcus Pembrey of the University of Bristol found that the sons of these early smokers had on average between 5kg and 10kg more body fat than their peers by the time they were teenagers. No significant effect was seen in the daughters of the male smokers, the researchers 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,” Professor Pembrey said.

“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,” he said.

When measured for body fat at ages 13, 15 and 17, the sons of the men who said they started smoking before 11 were consistently fatter than the sons of men who started smoking later or who had never smoked, according to the study, published in the European Journal of Human Genetics.

Other scientists were however sceptical of the claims, suggesting that the findings may simply be a chance event, rather than being statistically significant, given the relatively small sample size.

“The main claim of this report is unjustified. This study does not provide good evidence that fathers who started to smoke before age 11 have fatter teenage children as a result,” said Professor Sir Richard Peto, a medical epidemiologist at Oxford University.