Of her new weight loss, Kelly Clarkson recently told People Magazine that her ramped up fitness and improved diet were thanks to some encouragement from her music manager boyfriend, Brandon Blackstock.

The couple don't exercise together, exactly. "We did that once and I ... didn't like looking all red and gross, so I don't do that," Clarkson told People, adding that her desire to be attractive to her new beau motivation enough.

But what Clarkson may not realize is that having a boyfriend double as a gym buddy can actually do wonders for your workout -- and your relationship. Research shows that working out with a gym buddy helps you to stick with your fitness goals. And psychology researchers agree that working out together creates a better bond.

One University of Denver study found that couples who have fun together, by stepping away from responsibilities like childcare, bills and work, report happier marriages in the longrun. "The correlation between fun and marital happiness is high, and significant," lead researcher Howard Markman, co-director of the Center for Marital and Family Studies told USA Today at the time of the study's release.

But it's fine if you like different activities, Paul VanWiechen, director of exercise physiology at Cleveland Clinic Canada said in an editorial. "Research shows that the happiest couples are those who like to exercise together, yet also give each other the space to exercise apart. So, after you’ve hit the courts and she’s practiced downward dog, the two of you can take a walk."

While Clarkson and her new boyfriend might keep their workouts separate, here are some other celeb couples who are often spotted working out á deux:

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  • Jim Toth and Reese Witherspoon

    The couple are often snapped <a href="http://www.peoplestylewatch.com/people/stylewatch/package/gallery/0,,20222169_20470352_20919210,00.html" target="_hplink">jogging together</a> near their Santa Monica home. Even after she was hit by an elderly driver while jogging in 2011, Witherspoon <a href="http://www.usmagazine.com/celebrity-moms/news/pic-pregnant-reese-witherspoon-goes-jogging-2012254" target="_hplink">hasn't given up her habit </a>of running outside.

  • Gisele Bundchen and Tom Brady

    The supermodel and the quarterback still have to work for their chiseled bodies and that includes <a href="http://www.popsugar.com/Pictures-Gisele-Bundchen-Tom-Brady-Exercising-LA-Baby-Benjamin-8252445" target="_hplink">family hikes in Los Angeles</a>.

  • Rebecca Romijn and Jerry O'Connell

    The duo stick to a regular Bikram yoga habit and, according to an interview in <em>Us Magazine</em> also go for <a href="http://www.usmagazine.com/celebrity-body/news/rebecca-romijn-losing-baby-weight-was-the-hardest-thing-ive-ever-done-2012142" target="_hplink">long rides on their tandem bike</a>. All that sweating together helped Romijn lose baby weight after her twins, Dolly and Charlie were born in 2008, she told <em>Us</em>.

  • Fergie And Josh Duhamel

    Often seen jogging, the singer and her actor husband are known to hit the links, as well. Duhamel has said that exercising together is emblematic of how their marriage works. ""We motivate each other. She pushes me, and I push her," Duhamel <a href="http://www.people.com/people/article/0,,20482384,00.html" target="_hplink">told <em>People</em> last year</a>. "It's something that we've always done for each other, whether it's working out or in our life together."

  • Nick Lachey and Vanessa Manillo

    The new parents <a href="http://www.shape.com/celebrities/celebrity-triathletes-0?page=7" target="_hplink">are also triathletes</a>, completing a recent race with Lachey's brother Drew.

  • Liev Schriber and Naomi Watkins

    The actors are <a href="http://www.dailymail.co.uk/tvshowbiz/article-2098284/Naomi-Watts-takes-Liev-Schreiber-run-filming-The-Grandmothers-Australia.html" target="_hplink">often spotted jogging</a> together, but have also been known for city bike rides with their young children.

  • Alex Rodriguez and Cameron Diaz

    Although they've split, <a href="http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CEkQFjAB&url=http%3A%2F%2Fwww.huffingtonpost.com%2F2012%2F04%2F26%2Falex-rodriguez-talks-cameron-diaz_n_1455266.html&ei=lbq-T6jnJrGK6QHut73YCg&usg=AFQjCNFoI1fXYy4S87elfPMZzdMOJ-YrmQ" target="_hplink">there's still love</a> between the Yankee and his former flame. "She's one of the greatest humans," he gushed recently. All that good will could be in part thanks to the bonding workouts between the two, <a href="http://www.okmagazine.com/photos/hot-shots/cameron-diaz-alex-rodriguez-work-out-field-miami" target="_hplink">including strength training on a professional field</a> during spring training.

  • Justin Timberlake and Jessica Biel

    The soon-to-be married lovebirds <a href="http://www.huffingtonpost.com/2011/08/30/justin-timberlake-and-jessica-biel-spotted-bike-riding-in-toronto_n_941859.html" target="_hplink">bike</a> and jog together.

  • Trudie Styler and Sting

    Maintaining a 27-year marriage in Hollywood is nothing to sniff at and, according to Trudie and Sting the secret may be in one of their favorite joint activities: yoga. "Yoga helps with all relationships," Styler <a href="http://www.yogajournal.com/lifestyle/3006" target="_hplink">told <em>Yoga Journal</em></a>. "Working relationships, friendships, parenting -- because it helps with listening, patience, tolerance, understanding."

  • Tom Cruise And Katie Holmes

    Cruise and Holmes are <a href="http://www.popsugar.com/Photos-Tom-Cruise-Katie-Holmes-Jogging-Boston-Suri-Cruise-5162947" target="_hplink">regularly photographed</a> <a href="http://www.people.com/people/gallery/0,,20302077_20665931,00.html" target="_hplink">jogging together</a> wherever they go.