Researchers discovered that the love of wanting to keep fit is in your genes and can be passed on from generation to generation.
Conversely, the same is true about being a couch potato.
In the future, people who suffer from laziness could be treated with medicine that targets the genes that specifically promote activity.
Scientists from the University of California found that on laboratory mice activity levels could be enhanced by selective breeding – the process of breeding animals for particular genetic traits.
Their study showed that mice bred to enjoy running produce offspring that also like it, showing that the baby mice had inherited the trait of high activity.
Professor Theodore Garland Jr, a biologist and lead author, said: "Our findings have implications for human health...