Embarking on a low-calorie diet could potentially lead to negative mental health, researchers in Toronto, Canada, have revealed.

A new study, published in BMJ Nutrition, Prevention and Health, investigated how the adoption of restrictive diets could instigate depressive symptoms.

Using the National Health and Nutrition Examination Survey, researchers analyzed nearly 29,000 adults who reported their dietary habits and also completed a mental health questionnaire.

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Nearly 8% of these adults reported depressive symptoms.

Compared to those who did not follow a specific diet, those who stuck to a calorie-restrictive diet — including overweight individuals — saw an increase in depressive symptom severity, the study found.

People who followed a nutrient-restricted diet saw a larger increase in symptoms, while men who followed any diet reportedly showed "higher somatic symptom scores" compared to non-dieters.

The researchers concluded that there are "potential implications of widely followed diets on depressive symptoms, and a need for tailored dietary recommendations based on BMI and sex."

Potential limitations

Judith S. Beck, PhD, president of the Beck Institute for Cognitive Behavior Therapy in Pennsylvania, reacted to these findings in an interview with Fox News Digital.

The expert, who was not involved in the research, noted that it only showed an association between low-calorie diets and depression.

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"This is an important distinction, [because] correlation does not equal causation, and having a few depressive symptoms does not mean you have the condition of depression," she said.

Beck noted that depression and negative emotions can also be caused by multiple cognitive, emotional or behavioral factors that are "more directly associated with depressive symptoms."

Fostering healthy habits

Certified holistic nutritionist Robin DeCicco in New York City commented that most Americans would benefit from losing weight, as 70% of Americans are overweight or obese, according to the Centers for Disease Control and Prevention (CDC).

This can be done by reducing the intake of sugary drinks and processed foods, and learning how to incorporate more whole foods like lean protein, vegetables, fruits and nuts, recommended DeCicco, who also was not involved in the study.

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The nutritionist also warned against following fad diets.

"It's not sustainable or healthy to follow these trends because, most often, they are not educating the public on the type of nutrients you need to function mentally and physically, which is why it doesn’t surprise me that people can experience depressive and cognitive-affective symptoms when losing weight."

The quality of calories "matters dramatically," DeCicco noted.

"While weight loss is about calories in and calories out, it’s also about the type of calories and what we need for fuel, protection against disease, and mental and physical satisfaction," she said. 

"Food has the power to help us or harm us, and if we’re not eating certain foods known to promote mental well-being, we will definitely suffer from cognitive impairment and unstable mood."

As an example, cutting out fats because they’re high in calories — like salmon, avocado, olive oil and nuts — also cuts out nutrients like omega-3 fatty acids, which can reduce inflammation, prevent disease and improve cognition, mood and brain health, DeCicco noted.

"If someone wants to lose weight but also has a health history of cognitive decline or is diagnosed with depression, it is even more important to emphasize the food groups mentioned above," DeCicco added.

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Beck echoed the importance of eating in a "very healthy way," while also recommending that people consider cognitive behavioral therapy (CBT).

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"CBT helps people learn the cognitive (thinking) and behavioral skills they need to eat as healthily as possible given their circumstances, and to change their thinking so they can make long-term changes in their eating and improve their overall health," she said.

Fox News Digital reached out to the study researchers for comment.