As if concern for a partner's health and longevity weren't problematic enough, the very subject can become a significant source of tension between the two of you. Outdoor activities and mealtime, once the high points of your free time together, become flashpoints for argument. The next thing you know, one of you is doing dips while the other is dunking doughnuts -- and the distance between you is increasing. The impact on a love life can be profound.

Silent messages
The first-tier approach many people attempt is to have an open, honest exchange in which you express your concern as well as your support: I love you and want you to feel good, be healthy and live long. Initial overtures like this are valuable for opening the lines of communication and establishing a compassionate tone.

But they're not always well received, and defenses can go up fast. Food psychologist Brian Wansink, Ph.D., author of the book "Mindless Eating: Why We Eat More Than We Think," recommends another tack: Influence a partner's good health without him or her realizing it.

"A lot of the changes are best made under the radar, or there's going to be push-back," warns Wansink. He describes a program based on "stealth health" that sidesteps the difficulties of defensiveness and self-consciousness, both of which break down partner communications and potentially intensify bad habits.

Change the frame
For an experiment at his Cornell University food lab, Wansink took a group of people for a 2-mile walk. He told half that they would be walking for exercise and half that they were going on a nature walk. He found that those who perceived they were exercising ate hundreds more calories of food when they returned. They felt they had put themselves out and earned a big snack.

"The lesson here is that if you say, 'Hey, do you want to come exercise with me?,' the answer is going to be no," Wansink explains. "There may be some consequence afterward, too. But if it's reframed as a walk or doing something innocent together, it may be more warmly received."

Mastering the soft sell
Reconsidering the framework shifts the focus of a health approach and removes combative exchanges from the picture. A partner may be inspired to make changes on his or her own when motivated to engage in fun, healthy activities like bicycling with the kids or simply walking the dog every day.

Wansink has also found anecdotal evidence of success in a few studies that incorporate spring cleaning and a trip to Goodwill. One partner suggests cleaning out some closets and wardrobes, and in the process points out clothes the other partner looks good in. "It's a masked way of sending a message," says Wansink. "It borders on the subliminal, but the message seems to be heard."

These are the good old days
One young husband told Wansink that he resumed a program of weight-lifting after his wife related that she missed the "young version" of him she had married. She said she knew the younger man was still in there.

"She never said a thing about losing weight," Wansink recalls. "She said she missed the old him that was lighthearted and fun. It turns out that it was something he missed, too."

Untangling the knots
There is also an element of self-preservation in the stealth approach since it helps eliminate conflicts that can tie up a couple in knots, with frustration directed both outward to our spouses and inward to ourselves. Painful as it sometimes may be, it's important to understand that you can't impose change; it has to come from within the person who needs it.

By experimenting with a few creative solutions, we really can nudge our partners in the right direction. We can't make the change for them, but we can play a critical role in reawakening their inherent desire to be healthy.