Next time you consider ditching the gym in favour of a pizza and a film (for the fifth consecutive day) spare a thought for your mind.
Regular exercise - even light exercise such as going for a walk or gardening - may help prevent depression in later life.
Analysing the results of 26 years' worth of data, researchers found that 25 out of the 30 chosen studies mark a correlation between lack of exercise and depression in later life.
"I'm active so I wasn't surprised to find this, but 25 out of 30 showed a significant effect and that was unexpected," says George Mammen, Ph.D. candidate and co-author of the study.
"If you're not physically active, you should start," Mammem tells NBC News. "We usually think of exercise in terms of weight and how we look, but it's also a way to maintain mental health far into the future."
The study was carried out at The University Of Toronto and published in American Journal of Preventive Medicine.