While romantic relationships are good for mental health and happiness, a study published in the American Journal of Preventive Medicine noted that the average weight gain over 10 years for a woman with a partner and a baby was 9 kilos (20 lbs).
Annette Dobson, a professor of biostatistics at the University of Queensland, studied 6,458 Australian women and found that the 10-year weight gain for an average 63.5 kilo (140-lb) woman was 5 kilos (11 lbs) if she was childless with no partner.
If she had a partner but not a child, the average gain was 7 kilos (15 lbs) and if she had a baby and a partner, that gain jumped to 9 kilos. Over the decade of the study, all the women gained weight steadily – which some experts attribute to the availability of cheap, abundant food.
Sociologist Emily Fitzgibbons Shafer of Stanford University found that marriage leads to increased body mass index for all men and women, with an increased likelihood for African-American women.
Since having a partner is not likely to cause metabolic changes, the weight gain found by Dobson appears to be caused by altered behavior or a metabolic adjustment linked to pregnancy, the New York Times reported. Dobson said that women’s bodies may adjust to the increased weight linked to having a baby.