The two lifestyle changes were more effective in stabilising mental health than interacting with friends, following a routine or pursuing hobbies.
The study, carried out by researchers in Barcelona, observed 942 Spanish adults for one year.
At regular two-week intervals, participants were asked to rate the frequency at which they used 10 different coping behaviours, and their levels of anxiety and depression.
Following a balanced diet, not reading news about Covid-19 updates too often, physical exercise, staying outdoors and drinking water were associated with coping better.
Some behaviours which had been perceived as beneficial, such as talking with relatives and friends or taking up a hobby, had a smaller influence on people’s mental health.
Dr Joaquim Radua, a lead researcher of the study, said the results were “a little surprising”.
“Like many people, we had assumed that personal contact would play a bigger part in avoiding anxiety and depression during stressful times,” Radua said.
“On the basis of these results, we recommend that everybody follows a healthy/balanced diet, avoids watching stressful news too often, spends more time outdoors, does relaxing activities, and does physical exercise.”
Radua said that while the study focused on the mental health of people during Covid-19, further research could explore whether these factors could be applied to other stressful circumstances.
“These simple behaviours may prevent anxiety and depression, and prevention is better than cure,” Radua said.
Professor Catherine Harmer, from the department of psychiatry at the University of Oxford, who was not involved in the study, said the study provides “important insights” but further tests are needed.
“Future work is needed to test whether these associations are causal – is it these behaviours which cause improvements in mood or could it be the other way around – as we feel better we start to engage more positively with our environment?”
A report published by the Queensland Centre for Mental Health Research in October 2021 found that the prevalence of depression and anxiety across the world increased by more than a quarter during the first year of the pandemic.
Scientists concluded that there were an aditional 53 millino cases of major depressive dirsoders, and 76 million cases of anxiety.