Just 20 minutes of housework or gardening a week can act as anti depressants according to a study published in the British Journal of Sports Medicine.
The more strenuous and frequent the activity, the greater the effect in lifting one's spirits, the study found.
University College London researchers looked at a survey of 19,842 men and women taking part in the Scottish Health Survey to see how much exercise and what kind of activities they did every week. They were also asked about their state of mind before and after the activities.
The findings showed that daily physical activity reduced stress levels, irrespective of age and prolonged health problems.
The more active people were, the less likely they were to be depressed. Taking part in sports at least once a week lowered stress levels by 33%, while housework, gardening and walking could cut it by as much as 20%.
However, the study made it clear that light dusting or a lazy walk to the bus stop strictly did not count as 'active' exercise.
The activity needed to be for at least 20 minutes at a time, and had to leave the doer breathless.
According to experts, one theory as to why activity might enhance mood is that it prevents some biological risk factors for depression, including glucose intolerance, inflammation and cardiovascular problems.
"Many studies suggest benefits for mental health from exercise, and for the first time we have been able to quantify the amount of activity which seems to make a difference," said Mark Harmer of University College London.
"But it is a chicken and egg issue - as those who suffer from stress or anxiety may be less likely to take part in physical activity in the first place," Mark Harmer added.
Spokesman Richard Colwill of Sane, the mental health charity, said, "This study may offer hope to those suffering mental pain that small, manageable lifestyle changes can improve mental well being."
Another study in the journal found such exercise among the middle-aged and elderly may delay the ageing process.
Researchers at the University of Toronto found, after looking at 400 adults aged between 55 and 85, that regular aerobic exercise in middle age and beyond trains the body to use oxygen more effectively in generating energy.
The amount of oxygen we are able to consume is reduced with age, and therefore to stay healthy and appear youthful, more aerobic exercise such as jogging is required to convert the fat in the body into fuel for muscles.
According to the study, regular aerobic exercise seems to delay biological ageing by as much as 12 years.
Lorna Layward, research manager at Help The Aged, said it was "never too late" to start exercising. She added, "There has long been the assumption that retirement is about putting your feet up, but gradually we're getting the message across that keeping active is good for you in so many ways."