Analysing data from more than one million people, researchers discovered that people with poor fitness levels had a 75% increased risk of developing the mental health condition.
For the new study, published in the journal Preventive Medicine, researchers analysed data of 1,142,699 people collected for three studies.
Low fitness levels were linked to a 75% increased risk of depression. Meanwhile those with medium fitness levels had an increased risk of about 23%.
Cardiorespiratory fitness levels measure the ability of the circulatory and respiratory systems to supply oxygen to muscles during sustained physical activity.
Dr Helen Webberley, GP for Oxford Online Pharmacy, said she wasn’t surprised by the results of the study.
“Regular exercise benefits both body and mind and is crucial for general health and wellbeing,” she told The Huffington Post UK.
“This is due to two main factors, exercise increases the heart rate, pumping more blood around the body and into the brain and exercise increases endorphins and serotonin production and release.
“Endorphins give a temporary lift in mood where higher serotonin levels are associated with longer term mood improvement. SSRI (serotonin selective re-uptake inhibitors) are well-known anti-depressants as they increase serotonin levels and thus lift depression.”
Stephen Buckley, head of information at mental health charity Mind, echoed Dr Webberley’s comments: “We agree that exercise can have a positive effect on a person’s mental health.
“Research shows that exercise can be as effective as antidepressants in treating mild to moderate depression as it stimulates mood-enhancing endorphins.”
The charity has launched a sports programme called Get Set to Go, which hopes to help people “overcome the barriers to exercising, by choosing an activity which is suitable for them and enabling them to take the first step and get active to improve their physical and mental wellbeing”.
“At Mind we want people with mental health problems to enjoy exercise and see the benefits for their own recovery,” added Buckley.
For those looking to increase their fitness levels, Dr Webberley recommends brisk walks, swimming or riding a bike for 30 minutes every day.