Food and exercise can treat depression as well as a psychologist, our study found. And it's cheaper

Around 3.2 million Australians live with depression.

At the same time, few Australians meet recommended dietary or physical activity guidelines. What has one got to do with the other?

Our world-first trial, published this week, shows improving diet and doing more physical activity can be as effective as therapy with a psychologist for treating low-grade depression.

Previous studies (including our own) have found "lifestyle" therapies are effective for depression. But they have never been directly compared with psychological therapies—until now.

Amid a nation-wide shortage of mental health professionals, our research points to a potential solution. As we found lifestyle counseling was as effective as psychological therapy, our findings suggest dietitians and exercise physiologists may one day play a role in managing depression.

What did our study measure?

During the prolonged COVID lockdowns, Victorians' distress levels were high and widespread. Face-to-face mental health services were limited.

Our trial targeted people living in Victoria with elevated distress, meaning at least mild depression but not necessarily a diagnosed mental disorder. Typical symptoms included feeling down, hopeless, irritable or tearful.

We partnered with our local mental health service to recruit 182 adults and provided group-based sessions on Zoom. All participants took part in up to six sessions over eight weeks, facilitated by health professionals.

Half were randomly assigned to participate in a program co-facilitated by an accredited practicing dietitian and an exercise physiologist. That group—called the lifestyle program—developed nutrition and movement goals:

•     eating a wide variety of foods

•     choosing high-fiber plant foods

•     including high-quality fats

•     limiting discretionary foods, such as those high in saturated fats and added sugars
•  
•     doing enjoyable physical activity.

The second group took part in psychotherapy sessions convened by two psychologists. The psychotherapy program used cognitive behavioral therapy (CBT), the gold standard for treating depression in groups and when delivered remotely.

In both groups, participants could continue existing treatments (such as taking antidepressant medication). We gave both groups workbooks and hampers. The lifestyle group received a food hamper, while the psychotherapy group received items such as a coloring book, stress ball and head massager.

Lifestyle therapies just as effective

We found similar results in each program.

At the trial's beginning, we gave each participant a score based on their self-reported mental health. We measured them again at the end of the program.

Over eight weeks, those scores showed symptoms of depression reduced for participants in the lifestyle program (42%) and the psychotherapy program (37%). That difference was not statistically or clinically meaningful so we could conclude both treatments were as good as each other.

There were some differences between groups. People in the lifestyle program improved their diet, while those in the psychotherapy program felt they had increased their social support—meaning how connected they felt to other people—compared to at the start of the treatment.

Participants in both programs increased their physical activity. While this was expected for those in the lifestyle program, it was less expected for those in the psychotherapy program. It may be because they knew they were enrolled in a research study about lifestyle and subconsciously changed their activity patterns, or it could be a positive by-product of doing psychotherapy.

There was also not much difference in cost. The lifestyle program was slightly cheaper to deliver: A$482 per participant, versus $503 for psychotherapy. That's because hourly rates differ between dietitians and exercise physiologists, and psychologists.

What does this mean for mental health workforce shortages?

Demand for mental health services is increasing in Australia, while at the same time the workforce faces worsening nation-wide shortages.

Psychologists, who provide about half of all mental health services, can have long wait times. Our results suggest that, with the appropriate training and guidelines, allied health professionals who specialize in diet and exercise could help address this gap.

Lifestyle therapies can be combined with psychology sessions for multi-disciplinary care. But diet and exercise therapies could prove particularly effective for those on waitlists to see a psychologist, who may be receiving no other professional support while they wait.

Many dietitians and exercise physiologists already have advanced skills and expertise in motivating behavior change. Most accredited practicing dietitians are trained in managing eating disorders or gastrointestinal conditions, which commonly overlap with depression.

There is also a cost argument. It is overall cheaper to train a dietitian ($153,039) than a psychologist ($189,063)—and it takes less time.
Potential barriers

Australians with chronic conditions (such as diabetes) can access subsidized dietitian and exercise physiologist appointments under various Medicare treatment plans. Those with eating disorders can also access subsidized dietitian appointments. But mental health care plans for people with depression do not support subsidized sessions with dietitians or exercise physiologists, despite peak bodies urging them to do so.

Increased training, upskilling and Medicare subsidies would be needed to support dietitians and exercise physiologists to be involved in treating mental health issues.

Our training and clinical guidelines are intended to help clinicians practicing lifestyle-based mental health care within their scope of practice (activities a health care provider can undertake).

Future directions

Our trial took place during COVID lockdowns and examined people with at least mild symptoms of depression who did not necessarily have a mental disorder. We are seeking to replicate these findings and are now running a study open to Australians with mental health conditions such as major depression or bipolar disorder.

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