When you’re single, life seems to be all about you: your schedule, your time, your goals.

But when you become smitten by that special someone, things change. You first catch each other’s eye, you go on a first date, and then you wonder how you ever lived without this person in your life.

Unfortunately, there’s evidence out there that throws a wrench in the notion that being in a happy relationship is always beneficial to one’s health. New couples tend to go out more than established couples, which often means fewer healthy meals, and time spent sipping cocktails while gazing into each other’s eyes. While sweet and romantic, these new infatuations can also mean weight gain, which increases your risk of other health problems.

Whether your couple goals are Han and Leia or Posh and Becks, at least some of those goals should include keeping each other healthy.

Newlyweds Tend to Gain Weight

Anyone who has been married knows all too well about the work you need to put in to looking good on your wedding day, including months of exercise and diet. (And spray-tanning, if you’re on “Bridezillas.”)

But what happens after you’ve taken those perfect wedding photos?

One study that tracked the weights of over 8,000 people found that, on average, married women gain 24 pounds in the first five years of marriage. Women who cohabitate, but aren’t married, only gain 18 pounds, while women who are in a relationship but living separately gain 15 pounds.

Men also gain weight, but there weren’t many differences between men who were married and men who were just living with a partner.

The researchers concluded that living together increases both men and women’s risk for obesity. (The study only looked at straight couples, so the jury is still out on whether there are similar trends in non-heterosexual couples.)

Other research has found that young newlyweds who are happy with their marriage tend to put on extra weight. In contrast, couples who weren’t as satisfied with their relationship tend to gain less weight.

Researchers concluded that the reason why happy couples gain weight is because they are less motivated to maintain their weight when they don’t need to attract a mate.

So, if your partner has gained some weight, chances are high that they think you’re the one.

Weight Gain Is Contagious

In the 8,000 person study mentioned above, researchers noted that going from being single or dating, to married or living together, is positively associated with obesity. Women who live with a romantic partner have an increased chance of becoming obese within a year, and men’s odds increase within two years. As a whole, married couples are most likely to experience this weight gain within two years.

This is called “concordance.” One study found that if one person in a married couple becomes obese, their spouse has a 37 percent higher chance of becoming obese, too.

Most research on the topic of couple weight gain agrees that the cause is quite simple: behavior is contagious. When you’re living in close proximity with someone else — someone who you want to spend time with, that is — you’re more likely to eat the same things, and do the same activities.

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Married People Still Eat Healthier

Nine studies that looked at the behaviors of people in different parts of Europe all found that people who have never been married tend to have a lower body mass index.

However, they also found that married people were more likely to eat healthier foods. How does this make sense? The researchers think it’s because married people pay less attention to dietary fat, as well as to their body weight.

Also, married men were found to exercise less than single men, which links back to the notion of caring less about your appearance.

Exercise Together, Stay Healthy Together

If you’re in a happy relationship, you have to take care of each other’s hearts — and we don’t just mean romantically.

Here are some ways couples can take care of each other’s health:

Exercise Together

It can begin with a walk after dinner, and progress to running marathons together. If kids are preventing you from leaving the house at the same time, try an exercise video — the kids might even want to join in on the fun. Whatever it is, exercise can help fight off the dreaded relationship weight while spending time together.

Eat Out Less

When you dine out, you don’t have control over what goes into your food. Restaurants are havens for excess fat and salt, which can contribute to weight gain.

Choose Healthier Snacks

When it is time to stay in, stock your place with fruits, vegetables, and nuts instead of chips and other unhealthy snacks.

Don’t Skip Visits to the Doctor

Couples can also care for one another by getting routine health checks from their doctors, as well as keeping each other accountable for health goals.

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