During pregnancy – and maybe even whilst trying for a baby - most sensible women will usually decide to stop drinking and quit cigarettes in a boosted attempted to conceive, and then protect the health of the baby whilst in the womb. However, new research has suggested that men may also need to watch what they eat and drink, following advice usually reserved for women, for an obesity risk may be passed on to children through the father’s sperm. The Danish scientists involved in the new study discovered a series of genetic markers in the sperm of obese men, which have the chance of altering brain development and appetite control. It is interesting to note that these same changes were not present within the sperm of lean males. Although more research is clearly needed in order to confirm such a theory is definitive, the tentative finding – if confirmed in much bigger studies – could lead to pressure on overweight men to lose weight and get in shape prior to starting a family, which may boost the chances of a healthier child. “We don’t yet know if this is important. But if what we’ve found is transmitted to children and is doing something negative, it raises new questions about what do we need to do, and how long we need to do it before we conceive,” said Romain Barrès who led the study at the University of Copenhagen. Past studies have demonstrated that obesity risk is strongly linked to both their inherited genes and their surrounding environment. The combination of factors leads to childhood BMI increasing line with parental weight, whilst previous analysis of twins found that as much of 70% of the differences between people’s fat mass can be attributed to DNA. Researchers in the Danish study decide to look at the ‘epigenetic information’ found in the sperm of 10 obese men and 13 lean men. This information isn’t encoded in DNA, but is contained within other chemicals that work with DNA. One such example is the methyl molecules that can attach to specific genes and silence them. Epigenetics can function in different ways, by changing the the protein that wraps DNA (adding or removing chemical "tags" that alter the structure of DNA), or via genetic molecules called small RNAs. Reporting their findings in the journal Cell Metabolism, the researchers analysed the epigenetic marks on sperm from the two groups of men, formulating what they argue is a “distinct epigenome that characterises human obesity.” A few of the changes found change behavioural genes and eating “and could participate in predisposing the offspring to obesity”. The researchers next decided to study the epigenetic information contained in the sperm of 6 morbidly obese men both prior to, and after undergoing gastric bypass surgery. A week after surgery, the epigenetic markers on 1509 genes had found to be changed in the sperm, increasing to 3,910 after a year. Over half also differed between obese and lean men. It is uncertain if the epigenetic markers discovered are passed onto offspring, in addition to the extent of the effects if they indeed are passed on. Although a small proportion survives, the majority of such epigenetic information transmitted by sperm is eradicated during fertilisation. Barrès said added that the next step will be to conduct studies to investigate the sperm from obese fathers and IVF embryos they have donated after completing their families. Wolf Reik, head of epigenetics at the Babraham Institute in Cambridge said that studies in animals have shown that changes in nutrition can alter the epigenetic markers carried by sperm. “It’s totally unknown what happens to these marks after fertilisation. In some ways the signals need to survive the global wipeout system, which is why it’s even more remarkable,” he said. “How strong the effects are in human populations is totally unknown. It’s impossible to tell at this point. That’s why the study is provocative, but much more needs to be done.” Allan Pacey, professor of andrology at Sheffield University, commnted although the study was intriguing and could warrant further investigation, it is too early to say what the observations meant for human health. “Until we know more, would-be parents should just aim to be as healthy as possible at the time of conception and not be drawn to faddy diets or other activities in order to try and influence the health of their children in ways we don’t properly understand.”