To our knowledge, this is the first study to comprehensively explore the prospective associations between marital transitions and changes in fitness in men and women. Our findings suggest that marital status may affect fitness differently for men and women. For example, there was a decline in fitness in men who remained single. There was also a trend toward a larger decline in those who married. In contrast, among women, remaining single was associated with an increase in fitness, which was not seen in those who married. Both of these results are in line with our hypothesis that getting married has a negative effect on fitness. In men, this hypothesis was further supported by the finding that divorced men who remarried showed a decline in fitness relative to those who did not remarry. Moreover, in married men who divorced, there was a small increase in fitness (compared with men who remained married), adding further support to our hypothesis. The low numbers of women in the transition groups probably explain the large variability and lack of clear patterns in fitness change score results for the married and divorced women. It is important to highlight that the strength of the associations was modest, indicating that other factors, in addition to marital status, explain the observed changes in fitness levels.
Because of the lack of studies examining the association between marital status and change in fitness, we cannot compare our results with previous research. However, a number of studies have explored the relation between marriage and physical activity, with mixed findings (21
). Although most studies have reported that people getting married become less active (8
), others have found opposite results (22
). Our results do mirror the findings for women in the Australian Longitudinal Study of Women's Health, which show that physical activity levels fall in women who marry and in those who have a baby (9
). These decreases in physical activity are likely to be reflected in decreases in fitness. However, although we adjusted our analyses for physical activity, it is likely that our physical activity measure was not sufficiently sensitive to detect small changes in activity and to accurately examine whether changes in fitness could have been due to changes in physical activity.
Our results may also be explained by changes in weight that occur with change in marital status, as Australian data show that women who marry gain weight at a higher rate than those who do not, after adjustment for a wide range of potential confounders (23
). Likewise, marriage is associated with an increased risk for overweight/obesity (4
) and increases in body mass index (3
), while divorce is linked to decreases in body mass index (24
). The attenuation of the difference in fitness change scores after adjustment for change in body mass index in the single-married transition analysis for women provides some indication that changes in body mass index were implicated in the fitness change scores.
Because of the observational design of the present study and the concurrent measures of change in marital status and fitness, the direction of the associations shown here cannot be confirmed. Nevertheless, it is feasible that marital transitions, which are accompanied by significant lifestyle changes (10
), may impact fitness. In addition, current research supports the notions that physical fitness is positively correlated with body attractiveness (rated by women) and mating success in men (25
) and that women rate muscular men as sexier (26
). Consequently, fitter men may be more successful in the “marriage market” than their unfit peers. According to this theory, single men have the social pressure of keeping themselves fit to increase their attractiveness and find a partner, while married men do not any longer have that “requirement” or at least they have it at a lower extent. If the “marriage market” hypothesis (which suggests that married individuals, who are no longer concerned about attracting a mate, may allow their fitness level to decrease) is true, we should see a negative effect on fitness when getting married, which is in fact the main finding of this study.
Of note is that our results showed that marital transitions influence fitness in men but not so clearly in women. Although the low number of women in some of the transition categories may have influenced the results, it is also possible that the association between marital status and fitness is present only in men. The cross-sectional analyses performed in this study confirm the longitudinal analyses, suggesting that fitness differed across marital status groups at baseline in men, but no differences were observed in women. Returning to attractiveness and the “marriage market” hypothesis discussed above, it has been reported that women's attractiveness might not be related to fitness or strength/muscularity (as it is the case in men) but to other traits, such as a narrow waist/hip ratio (27
). This may at least partially explain the sex differences observed in our study.
The current study has limitations. First, a smaller number of women than men participated in the study; thus, the findings observed in men may have more strength than those observed in women. Of note is that, for some marital transitions, for example, from married to divorced and from divorced to remarried, the pattern of the association clearly differed between women and men. Caution should be taken when interpreting these differences, because of the small sample size and the large heterogeneity observed in these transition groups in women. Second, most of the ACLS participants were married at baseline (>85%). According to the US Census in 2000, 52% of the US adults were married and living with their spouse. Therefore, being married is overrepresented in this cohort. Nevertheless, for marital transitions that occurred during the ~3 years’ follow up, the sample sizes were similar across categories. Third, the lack of information about having/not having children is another limitation of the present study. Because many couples now delay getting married until they want to have children and because having children places notable constraints on the time available for structured exercise (28
), the presence of children may partially explain the decline in fitness seen in the transition from being single to being married (23
). Future studies should address this issue in relation to fitness. Fourth, other categories of marital status, such as “separated” or “de facto,” were not included in the questionnaire used in this study, which could be a source of error. Nevertheless, we think that those living in a “de facto” relationship may have identified as “married” and that those living alone as “single.” We cannot confirm this, and we do not know if lifestyle factors and fitness are different in married and de facto couples or in single and separated individuals. Finally, we did not have sufficient information on physical activity frequency and intensity. Therefore, we could not account for exercise volume in this study. Future studies should include such information whenever possible.
The relatively large number of participants with measurements for all the study exposures, outcomes, and confounders at 2 time points, particularly men, as well as the well-standardized and objective measure of fitness, is a notable strength of this study.
In conclusion, the current findings, based on data from nearly 9,000 people from the ACLS followed up for a median period of ~3 years, suggest that transitions to being married (i.e., from single to married or from divorced to remarried) are associated with a modest reduction, while divorce is associated with a modest increase, in fitness levels in men. The results suggest that these patterns may be different in women, but further research is required to confirm this.