New study suggests calorie restriction may be linked to worsening depression

Experts recommend consulting a medical professional before attempting to lose weight. Sabina Eivazova/iStockphoto/Getty Images via CNN Newsource

Going too far with a diet might have serious impacts on your mental health.

Cutting your calories down too far could be linked with worse depression symptoms, new research suggests.

A study published Tuesday in the journal BMJ Nutrition, Prevention & Health looked at data from more than 28,000 adults from the National Health and Nutrition Examination Survey, which surveyed participants on their diet quality and depressive symptoms.

People who followed a calorie-restrictive diet, particularly men and people with a body mass index considered overweight, were more likely to have higher symptoms of depression, according to the data.

Quality of diet also mattered. People who reported a diet with more ultraprocessed foods, refined carbs, saturated fats, processed meats and sweets were more likely to report higher levels of depression and those who ate more of a Mediterranean-style diet generally had lower risk of depression, the study showed.

“The findings suggest caution with overly restrictive or unbalanced diets, particularly for people already experiencing weight-related stress or challenges,” said lead study author Dr. Venkat Bhat, psychiatrist, clinician-researcher and director of the Interventional Psychiatry Program at St. Michael’s Hospital and University of Toronto.

Instead, Bhat suggests “opting for balanced, sustainable dietary changes that meet nutritional needs and consider individual psychological impacts may help minimize potential negative effects on mood.”

A different finding from previous studies

There are some limitations to consider when looking at the results. The design of the study can only show associations, not definitively say that calorie restriction causes an increase in depression symptoms, Bhat said.

In addition, the study surveyed people on their dietary patterns, which leaves room for error, said Dr. Kary Woodruff, associate professor (lecturer) and director of the nutrition and integrated physiology department’s coordinated master’s program at the University of Utah. She was not involved in the research.

“I could think I am on a calorie-restricted diet when in fact I may be in a calorie surplus — there’s no way to verify participant’s calorie-restriction status,” Woodruff said.

The study is large and controlled for other factors that could drive the associations found, but its findings contrast with those of previous studies around the topic of calorie restriction and depression, Bhat said.

Other studies have found that calorie-restricted diets reduce depressive symptoms, said Dr. Johanna Keeler, postdoctoral researcher at King’s College London. Keeler was not involved in the study.

One difference is that previous research, including a 2023 paper that Keeler coauthored, studied restrictive diets supervised by medical professional.

“Therefore, these findings might reflect that unsupervised dieting, which can produce nutritional deficiencies, might not be good for depressive symptoms,” Keeler said.

More research and randomized control trials may be needed to fully understand how dieting impacts mental health, Bhat said.

When restriction might impact depression

There are several reasons why the calorie restriction seen in the most recent study might be associated with a negative mental health impact.

Previous studies, including Keeler’s, found that low-calorie diets that resulted in weight loss for people classified as overweight or obese was associated with reduced depression symptoms.

That could be because of physiological changes, improved physical mobility or increased positive social feedback, Keeler said.

“Embarking on a calorie restricted diet without experiencing weight loss, or experiencing ‘weight cycling’ might not produce improvements in depression, and on top of that may be frustrating or disheartening to individuals, causing an increase in depression,” Keeler said in an email.

When calories are too restricted or not enough nutrients are being provided by a diet, there could be an interruption in physical processes that could lead to fatigue, sleep problems and difficulty concentrating, Keeler added.

Extreme dieting patterns also are linked to increased anxiety and a higher risk for an eating disorder, Woodruff said.

“The key is to examine what — and how much — is being restricted. Focusing on following a healthful eating pattern that supports mild to moderate caloric restriction may improve depressive symptoms and mood, whereas extreme behaviors can exacerbate mental, emotional, and physical health,” she said via email.

Finding balance

How a person responds to a diet varies among individuals, and the results of the study highlight the need for personalized dietary recommendations and consideration of psychological factors in addition to physical health, Bhat said.

With so much contrasting advice when it comes to nutrition and what’s the best approach for your own nutrition, Keeler recommends input from a medical professional before starting any weight loss efforts.

Even if you want to lose weight, focusing too much on heavy calorie restriction might not be the most sustainable option, said Natalie Mokari, a dietitian in Charlotte, North Carolina.

Instead, she recommends small changes to move toward a more balanced lifestyle.

Start by looking at your meals, Mokari said. Does your plate have a protein, carbohydrate, healthy fat, and some fiber and nutrients through fruits and vegetables?

Try prioritizing adding in the nutrition you need first, then see whether there are elements you don’t need anymore, she said. Perhaps if you eat from all of your food groups and slow your meals down, you will realize you don’t need to grab a second helping or you won’t feel the same urgency to grab a sweet treat after, Mokari said.

“Regardless of weight loss, improving dietary quality can significantly improve overall health and quality of life,” Woodruff said. “Consider working with a registered dietitian to understand what a healthful dietary pattern can look like for you.”