In the 2011 comedy "What's Your Number," Ally (Anna Faris) decides to revisit ex-boyfriends in hopes that one of them will turn out to be "the one."

In one scene, she runs into an ex, Donald, and flashes back to their less-than-healthy relationship. Both were overweight. Ally suggests cooking, but Donald wants to go out to eat.

Back in the present, both are clearly impressed by one another's newly acquired fit physiques.

Relationship-related weight gain seems to be an accepted fact these days. The theory is, as we get comfortable with our partner, we stop caring as much about how we look, our nutrition, and our exercise level.

But a new study looked at more than 2,000 people who were in a marriage or long-term relationship and found that a truly supportive relationship was associated with lower body weight in middle age.

If you've both been gaining weight, take the time to assess how you can be more supportive to one another, not just about nutrition and exercise (vitally important) but also about everyday life (that could eliminate eating due to stress, especially late at night).

Talk to one another about becoming "better health buddies." Find exercises to do together, like daily walking goals (10,000 steps), and plan for ways to meet them.

Take a cooking class, or find and shop for healthy recipes to prepare. We bet working toward the common goal of a healthier lifestyle does more than make you feel 10 years younger; it'll add intimate zip to your relationship, too.