Some apps offer users money for checking in at the gym; others create games with a little friendly competition. But for some, exercising is still a chore, and even a wad of cash or a virtual trophy can’t make the treadmill seem more appealing than the couch. A new study adds to a growing body of research suggesting that some people are genetically predisposed to be physically active, while others have genes that make them more likely to be more sedentary Phenotypic and molecular differences between rats selectively bred to run high versus low nightly distances. Roberts, M.D., Brown, J.D., Company, J.M., et al. University of Missouri. American Journal of Physiology 2013 Apr 3. Epub ahead of print. . This research comes at a time when rates of physical inactivity — and related issues including obesity — are skyrocketing; and it’s a reminder that some people may need a little boost when it comes to achieving their health and fitness goals.

What’s the Deal?

Exercise Addiction In the most recent study, researchers used a selective breeding process to produce two distinct groups of rats Phenotypic and molecular differences between rats selectively bred to run high versus low nightly distances. Roberts, M.D., Brown, J.D., Company, J.M., et al. University of Missouri. American Journal of Physiology 2013 Apr 3. Epub ahead of print. . Some preferred to run long distances and could run fast; others were relative slowpokes that didn’t make it very far.

Perhaps unsurprisingly, the rats that liked to run had a lower average body mass than the rats who didn’t. They also had higher levels of mitochondria, the cellular structures that produce energy. But when researchers did a little snooping around the rats’ brains, they found 36 genes that differed between the two groups.

When it comes to rodents, this study is hardly the first to suggest that genetics are a key factor in how much they’re willing to exercise AMP-activated protein kinase (AMPK) beta1beta2 muscle null mice reveal an essential role for AMPK in maintaining mitrochondrial conduct and glucose uptake during exercise. O’Neill, H.M, Maarbjerg, S.J., Crane, J.D., et al. Department of Medicine, McMaster University, Hamilton, ON, Canada. Proceedings of National Academy of Science 2011 Sep 20;108(38):16092-7. An Epistatic Genetic Basis for Physical Activity Traits in Mice. Leamy, L.J., Pomp, D., Lightfoot, J.T. Department of Biology, University of North Carolina at Charlotte, Charlotte, NC, USA. The Journal of Heredity 2008 Nov-Dec;99(6):639-46. . Other research shows that the same idea applies to humans, and some people are genetically predisposed to be more physically active Current understanding of the genetic basis for physical activity. Lightfoot, J.T. Huffines' Institute for Sports Medicine and Human Performance, Department of Health and Kinesiology, Texas A&M University, College Station, TX, USA. The Journal of Nutrition 2011 Mar;141(3):526-30. Genetic influences on physical activity in young adults: a twin study. Mustelin, L., Joutsi, J., Latvala, A., et al. Hjelt Institute, Twin Research Unit, University of Helsinki, Helsinki, Finland. Medicine and Science in Sports and Exercise 2012 Jul;44(7):1293-301. . Over the past few years, researchers have pinpointed specific human genes that influence our willingness to work out Genetics of physical activity and physical inactivity in humans. de Vilhena y Santos, D.M., Katzmarzyk, P.T., Seabra, A.F., et al. CIFI2D, Faculty of Sports, University of Porto, Rua Dr. Plácido Costa, Porto, Portugal. Behavior Genetics 2012 Jul;42(4):559-78. Driven to be inactive? The genetics of physical inactivity. Moore-Harrison, T. Lightfoot, J.T. Department of Kinesiology, University of North Carolina at Charlotte, North Carolina, USA. Progress in molecular biology and translational science 2010;94:271-90. . In fact, scientists have found certain genes found in physically active people may also be responsible for their lower levels of body fat Genetic analysis of self-reported physical activity and adiposity: the Southwest Ohio Family Study. Choh, A.C., Demerath, E.W., Lee, M., et al. Lifespan Health Research Center, Wright State University Boonshoft School of Medicine, Kettering, OH, USA. Public Health Nutrition 2009 Aug;12(8):1052-60. .

Is It Legit?

Yes, to a certain extent. Although other similar studies have involved humans, this latest study only tested rats, which aren’t always the best model for humans. Even if these findings do apply to humans, this research is hardly an excuse for anyone to swap a gym routine for an all-day TV marathon. And it definitely doesn’t mean that people who aren’t genetically predisposed to love physical fitness are destined to be out of shape.

But it is a reminder that some people may need a little more incentive to lace up those running sneaks than others. Sometimes that means grabbing a pal who won’t let us ditch our next gym session; other times motivation is all about a solid workout playlist (hey, Beyonce). Research is also increasingly finding that money is a great incentive for weight loss specifically. Ultimately, the key to health and fitness is finding what works for you.

Photo by Aleksandra Flora

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