Working mothers with steady relationships are the healthiest women - while housewives are the most likely to be obese, a UK study suggests.
Mothers should be helped if they want to work, the researchers say
Experts followed 1,200 women from 15 to 54 in the Journal of Epidemiology and Community Health study.
Some 23% of those with multiple roles were obese, compared with 38% among the long-term homemakers.
The researchers say the findings show the short-term stress of juggling roles is outweighed by long-term benefits.
They used data on women taking part in the Medical Research Council's National Study of Health and Development, which tracks the long-term health of British men and women born in 1946.
The women's health at 26 and at 54 was assessed using a questionnaire, while details were taken about employment history, marital status, and whether they had children, for every decade from their mid-20s.
Their weight and height were also measured at regular intervals.
Analysis of the information showed that by the age of 54 women who had been partners, parents and employees were significantly less likely to report ill health than women who did not fulfil all three roles.
Women who had been homemakers for all or most of their lives, and had not held down a job, were most likely to say their health was poor, followed by lone mothers and childless women.
Thirty-eight per cent of long-term homemakers were obese compared with 23% of working mothers who had had steady relationships.
Weight gain also tended to occur at a faster rate among the homemakers.
The researchers, led by Dr Anne McMunn of UCL's Department of Epidemiology and Public Health, said the findings showed good health was the result, not the cause, of adopting multiple roles during the women's lives.
Dr McMunn added: "The study shows women who combine employment with motherhood and partnership do end up healthier."
She suggested the women who had stayed at home were likely to have gained weight because they exercised less and ate more, perhaps from making home-cooked dinners and eating their children's left-overs.
Dr McMunn said the study did look at a specific generation of women, but that its lessons remained valid.
"It shows that we probably should be supporting women to be able to be part of the labour market as well as mothers.
"And it gives the message that the long-term health benefits of being a working mother outweigh the short-term stress."
'New men' still needed
Cary Cooper, professor of organisational psychology and health at Lancaster University, said: "There is no question that working mums suffer short term stress from juggling their personal and business life with, in many cases, little real support from their partners.
"But this constant juggling also means that women need, by necessity, to look after their health, are better able to prioritise their demands and are less sedentary than others."
But he added: "This does not mean that this should provide men with an excuse not to own up to their responsibilities in taking some of the burdens off of the juggling working mums - we still need 'new men'!"
Dr Gillian Braunold, a GP in Kilburn, north London, said: "There has been an argument that women who juggle work and motherhood don't have time to eat well, and that they have a lot of fast food.
"But they are probably running on adrenalin a lot of the time, and are always moving around.
"At the end of the day, you are what you eat and how much you exercise."