is there a laziness gene

Have you ever wondered why you can't get off the couch and exercise — despite paying for an expensive gym membership, despite your New Year's resolutions, even despite the doctor's scolding at your last check-up? Turns out that your inertia may be coded right into your genes.

Based on some intriguing, preliminary studies in animals, J. Timothy Lightfoot, a kinesiologist, and his team at University of North Carolina, Charlotte, suggest that genetics may indeed predispose some of us for sloth.

why, given all we know about the overwhelming health benefits of physical activity, do so many people still choose not to exercise.

There are two theories, genes may affect either the way muscles work — perhaps causing them to use energy more efficiently and preventing fatigue — or some higher-order biochemical circuit in the brain, such as levels of the neurotransmitters dopamine or serotonin. Researchers have examined the muscle tissue of the mice in the study, however, and early data, which has not yet been published, suggests there's no difference in their function. So researchers' best guess is that the drive to exercise is at least partly influenced by brain chemicals — a reasonable hypothesis, given that dopamine or serotonin plays a significant role in several human drives and behaviors, including hunger, addiction, mood and movement disorders like Parkinson's disease.