Being married makes men gain weight, and the early days of fatherhood add to the problem, finds new research from the University of Bath’s School of Management.

The study shows that married men have a higher Body Mass Index (BMI) than their non-married counterparts, adding approximately three pounds or 1.4kg to the scales.

There’s no effect on male BMI if their wife becomes pregnant, but in the early years after childbirth men gain weight. It takes the period just before and after divorce to register a dip in male BMI.

The study shows that married men are on average 1.4 Kg heavier than their non-married counterparts

The findings clear up the confusion of competing theories put forward by social scientists linking BMI to marital status. It confirms the idea that people who are single but seeking marriage have more incentive to stay fit and make more effort than those who are married.

It also supports the theory that marriage leads to more social occasions involving richer foods, or more regular meals for men; while putting paid to the idea that married couples have better physical health because of increased social support.

The study of heterosexual couple in the United States, between 1999 and 2013, used data from the Panel Study of Income Dynamics and is published in the journal Social Science and Medicine.

Dr Joanna Syrda, Business Economist in the School of Management, said: “It’s useful for individuals to understand which social factors may influence weight gain, especially common ones such as marriage and parenthood, so that they can make informed decisions about their health and well-being. For married men who want to avoid BMI increases that will mean being mindful of their own changing motivation, behaviour and eating habits.

“Given major public health concerns about obesity, understanding more about the social science factors that can cause weight fluctuation is important.”