In a study of severely obese patients scheduled to undergo weight-loss surgery, those who were physically active were less likely to suffer from depression than similar patients who were sedentary.
Physical activity also reduced the likelihood that these patients would need antidepressants or counselling for depression or anxiety, the observational study found.
It doesn't take much exercise, the study revealed. Just eight minutes of moderate physical activity each day can reduce the odds of severely obese adults needing treatment for depression or anxiety by 92%.
One "goal of this study was to determine physical activity thresholds that best differentiated mental health status. We were surprised that the thresholds were really low," study author Wendy King, an epidemiologist at Pitt Public Health, said in a University of Pittsburgh Medical Center news release.
How the study was done
The three-year study examined how much physical activity 850 adults got in the week before they had weight-loss surgery, also known as bariatric surgery, at one of 10 different hospitals.
Participants wore an electronic device on their ankle to track the amount of activity they got. They also completed a questionnaire designed to assess their mental health. In the survey, patients were asked to report any symptoms of depression as well as any treatment they received for mental or emotional problems, including anxiety and depression.
About one-third of the participants had symptoms of depression. The researchers also found two in five patients had taken medication or received counseling for either depression or anxiety.
Eight minutes of moderate exercising
Although eight minutes of moderate physical activity daily had the most dramatic effect, the researchers found that even just 4 750 steps a day (less than half the 10 000 steps recommended for a healthy adult) reduced the odds of depression or anxiety treatment for adults with severe obesity by 81%.
"It could be that, in this population, important mental health benefits can be gained by simply not being sedentary," King noted.
The study authors pointed out that more research is needed to prove that patients' physical activity influences their mental health.
"Results of the study are provocative, but we would need further research to verify that physical activity was responsible for lower levels of depressive symptoms in this patient population," said study co-author Melissa Kalarchian, an associate professor at Western Psychiatric Institute and Clinic of UPMC in the news release.
"Nonetheless, physical activity is a key component of behavioural weight management, and it is encouraging to consider that it may have a favourable impact on mental health as well."
7% of the general population has anxiety disorder
While 7% of the general population has major depressive disorder and 10% has anxiety disorder, adults who are severely obese are nearly twice as likely to be affected by these conditions.
The researchers said that depression and anxiety should be treated before weight-loss surgery, since these mental health issues can have a negative impact on long-term surgically induced weight loss.
The study was published in the February issue of the Journal of Psychosomatic Research.
The US Centers for Disease Control and Prevention provides more information on the benefits of physical activity.