Public Release: 

Men who started smoking before age 11 had fatter sons

University of Bristol

Men who started smoking regularly before the age of 11 had sons who, on average, had 5-10kg more body fat than their peers by the time they were in their teens, according to new research from the Children of the 90s study at the University of Bristol. The researchers say this could indicate that exposure to tobacco smoke before the start of puberty may lead to metabolic changes in the next generation.

The effect, although present, was not seen to the same degree in daughters. Many other factors, including genetic factors and the father's weight, were taken into account but none could explain the change. In fact, the fathers who started smoking before 11 tended to have lower BMIs (body mass index) on average.

The effect was not seen in the sons of men who started smoking after the age of 11, suggesting that the period before the start of puberty is a particularly sensitive period for environmental exposures. This is in line with a prior hypothesis by the authors based on earlier Swedish studies that linked paternal ancestor's food supply in mid childhood with mortality rates in grandchildren.

Of the 9,886 fathers enrolled in the study, 5,376 (54 per cent) were smokers at some time and, of these, 166 (3 per cent) reported smoking regularly before the age of 11.

When measured at age 13, 15 and 17, the sons of the men in the latter category had the highest BMIs at each time point compared with the sons of men who had started smoking later or who had never smoked. More precisely, these boys had markedly higher levels of fat mass (recorded using whole-body scans), ranging from an extra 5kg to 10kg between ages 13 and 17.

The research was funded by the UK Medical Research Council (MRC) and is published today [2 April 2014] in the European Journal of Human Genetics.

Speaking about the findings, senior author, 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.'

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.'


1. The paper, Northstone, K et al, 'Prepubertal start of father's smoking and increased body fat in his sons: further characterisation of paternal transgenerational responses' is published today [2 April 2014] in the European Journal of Human Genetics, doi:10.1038/ejhg.2014.31. The paper can be downloaded.

2. Although smoking rates in the UK are on the decline, worldwide almost one billion men smoke - about 35 per cent of men in developed countries and 50 per cent in developing countries. Over 300 million men in China smoke; that's equal to the entire population of the USA. In Russia more than 60 per cent of men smoke. Source: World Health Organization,

3. For facts and stats on smoking in the UK, visit or call the Action on Smoking and Health (ASH) press office on 020 7404 0242.

4. For the latest in-depth figures on smoking among young people in England, see 'Smoking, Drinking and Drug Use Among Young People in England 2012' published by the Health and Social Care Information Centre

5. This is the 1,000th paper published by Children of the 90s.

6. In the 24 years since Children of the 90s published its first paper, we have asked our 34,000 participants (of whom more than 500 now live abroad) more than 500,000 questions, processed 1.4 million biological samples and received research requests from almost 600 academics worldwide. Visit to find out more.

7. Children of the 90s has been awarded £7.75 million by the UK Medical Research Council and the Wellcome Trust from 1 April 2014 to fund its work for the next five years. It also receives financial support from the University of Bristol.

8. For all media enquiries contact Dara O'Hare, communications manager at Children of the 90s on +44 (0)117 331 0077, +44 (0)7891 549144, email

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