However, when men did most of the childcare, there was no such negative impact on the quality of the relationship or time in the bedroom.In fact, they were as happy as couples who shared childcare equally.
Winter Wonderland is an annual event in London's Hyde park with fair ground rides, Christmas stalls, markets and entertainment for all ages.
Dr Daniel Carlson, study leader and assistant professor of sociology, said the study shed new light on the importance of men being involved in childcare - rather than women, as is traditionally focussed on."One of the most important findings is that the only childcare arrangement that appears really problematic for the quality of both a couple's relationship and sex life is when the woman does most or all of the childcare," Dr Carlson told the BBC."It suggests that father engagement and sharing childcare with one's partner is important to both sexes," he added in the report. Other commentators told the BBC that men who invest more time in looking after their children probably invest more in the relationship overall.
In that sense, the study could say more about the kind of couples who share responsibilities, rather than the direct effect of childcare hours on sex lives.
Vegetarians tend to opt for healthier lifestyles, a generally more active daily regime, than meat-eaters.
This, say critics, may explain the vegetarian group's higher scores in tests, rather than the food they consume.