Heavily Ever After? Living Together and Its Links to Obesity

by Danielle Taubman on February 12, 2013

Whether or not we are single or hitched, as Valentine’s Day approaches, the many couples around us often become more apparent.  We may start to pay closer attention to couples holding hands, gazing into one another’s eyes, and looking hopelessly in love. The singles often begin to resent their solo status just a little bit more this month, seeing all the new engagement announcements on their Facebook news feeds and wishing that they too were being proposed to.

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And beyond the feelings associated with love and commitment, marriage does have clear health benefits.  Marital status is associated with improved health and decreased health-risk behavior, especially for men.  Specifically, marriage is linked to lower mortality and decreases in legal and illegal drug use.

Yet, despite the appeal of love and marriage this Valentine’s Day season, a study by Natalie The and Penny Gordon-Larsen, two nutrition epidemiologists at UNC School of Public Health suggests that marriage and cohabitation may lead to obesity (a BMI greater than 30).


Well hopefully I’ve made someone who is despairingly unattached out there (of course I’m aware that you can be happily single as well!) feel a bit better about their relationship status, if only for a moment.

Studies show that Body Mass Index (BMI) is highly correlated between spouses and cohabiters, which may result from one of two situations:

  1. Assortative mating- the propensity for individuals to select romantic partners with similar (health) behaviors or body types.  (According to Kail and Cavanaugh’s book, Human Development: a Life-Span View, this principal also works in the non-health sense, for dimensions like religious beliefs, age, socioeconomic status, intelligence, and political ideology. Naturally, liberals and conservatives wouldn’t ever choose to associate with one another.)
  2. Shared household environment- living in the same territory, which means sharing the same foods in your pantry and lounging on the couch to watch shows at the same times.

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The and Gordon-Larsen wanted to disentangle these two situations to see whether living in the same environment—rather than assortative mating—may be the main obesity-inducing culprit.  They specifically investigated whether shared household environment and duration of time spent living together could be related to the development of concordant obesity (similar BMI measurements).

The researchers used data from the National Longitudinal Study of Adolescent Health (Add Health), which is a sample of adolescents.  These same adolescents have been followed into young adulthood with four in-home surveys.  So, the researchers used secondary data (data collected previously)—very resourceful of them!

They supplemented this data with additional research among subjects’ partners—whether they were dating, living together, or married (so they didn’t have to feel left out!)  The end result of this sampling allowed The and Gordon-Larsen to examine data from 1,293 romantic partners (*subjects who were already obese were excluded because they were interested in the development of obesity).

They looked at three subgroups: couples who were dating, married, and cohabiting.  Within each group, they compared each partner’s weight status, his or her physical activity level, and his or her degree of sedentary behavior (i.e. vegging out on the couch).

What were they looking for exactly?

If assortative mating were the source of the similarity in BMI, then weight status, physical activity, and sedentary behavior, would have to be in line across the different types of romantic relationships (dating, married, and cohabiting).  If this was not the case, and similar BMI values between partners were found only in married and cohabiting couples, the shared living quarters argument would win out.

What did they find?

In general, the people who transitioned from being single or dating at the start of the study, to cohabitation or marriage at the time they filled out the third survey, had increased odds of obesity. However, this was not the case for the people who went from single to dating.  So, common environmental influences seemed to be in effect.

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In fact, regardless of the type of romantic relationship, couples who lived together for over two years were significantly more likely to consist of one or two obese, less physically active, and more sedentary partners.  Those who were married were the most likely duo to become obese…no wonder some people are so afraid to tie the knot!

Also, duration of living together is relevant here. The longer the couples lived together, the more parallel they were to each other in terms of weight status, physical activity/inactivity. And the higher the incidence of obesity.  As a side note because it’s a pretty cool conversation starter, research by Robert Zajonc, from the University of Michigan this time (Go Blue!), shows that the longer couples date the more they look alike. Sounds pretty silly, but its grounded in science. Who knew?

Why all the excess weight?

When you’re living together, mealtime may become a more important occasion, meaning larger portion sizes and more calories. Couples may not make as much of an effort to hit the gym.  And, the sentiment of feeling truly comfortable with someone may lead them to throw on the sweats (I promise I have nothing against sweatpants) without the slightest intention of working out.

So does this mean we should remain single if we don’t want to pack on the pounds? Not necessarily.  First of all, it’s important to critique a number of different available studies before drawing any definite conclusions.  And, we can take action so we don’t become another unsettling statistic.

Channeling our public healthiness, how can we prevent this unfortunate reality?

Couples can find activities like exercising together to stay healthy and physically fit.  Interventions can target the household environment to help establish healthy behavior patterns around diet and exercise.  Since research shows that couples are often in sync with each other in terms of health behaviors, reciprocal encouragement between partners is a must.  Couples can draw on inspiration from each other so they develop—and stick with—a routine together.

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A spanking new study by Amy Gorin from the University of Connecticut demonstrates the value of this team effort.  It suggests that attending a behavioral weight loss program with a romantic partner in conjunction with bringing items such as exercise equipment and portion plates into the home, improved (initial) weight loss.  Well, initial weight loss is certainly a good start!

Happy (early) Valentine’s Day!