Study on the Impact of Diets on Depressive Symptoms

June 10, 2025, 12:02 pm | Read time: 3 minutes

A new study has examined whether certain diets are associated with a stronger manifestation of depressive symptoms. The researchers found a notable link between a low-carb diet and the psychological issues studied. One gender was more affected. FITBOOK explains the results in detail.

A “healthy” diet is associated with “fewer depressive symptoms” in research, according to the introduction of the new study.¹ However, there is no standardized definition for a diet that meets this description. Often, in an effort to improve their health, patients are prescribed specific dietary changes or diets. But what about mental health? The study examined whether people on diets are more likely to suffer from depressive symptoms—and whether any trends differ based on gender and weight.

Study on Diets and Depressive Symptoms

For the study, researchers analyzed health data from 28,525 U.S. women and men from various cycles of the National Health and Nutrition Examination Survey (NHANES). NHANES is a large-scale health study that collects data on participants’ dietary habits, medical findings, and self-reports on mental health and lifestyle.² To assess the presence or severity of depressive symptoms, the PHQ-9 patient questionnaire, commonly used in medical practice, was employed.³ It consists of nine questions, with responses scored; a score of 10 or more indicates serious mental health issues.

Study Procedure

The researchers divided the participants into four groups:

1. Individuals with a normal diet (no diet),
2. those on a calorie-reduced diet,
3. women and men following a specific restrictive diet (either low-fat or low-carb), and
4. individuals following common diet plans, such as DASH.

The distribution was very uneven. The majority of participants (more than 87 percent) did not follow a diet. In the calorie reduction group, the proportion of overweight and obese individuals was higher. The researchers compared the average PHQ-9 scores of the groups. Additionally, they conducted further analysis by gender and BMI categories.

Results

The evaluation revealed a clear picture. Participants in the second group, who followed a calorie-reduced diet, scored, on average, about 0.29 points higher on the PHQ-9 scale for depressive symptoms compared to the control group without diets. The indications were even more pronounced among overweight participants: If they followed a calorie-reduced diet, their scores were, on average, 0.46 points higher. With a low-carb diet, their depression scores increased by an average of 0.61 points. According to the study report, these correlations were particularly evident in men: All diet forms were associated with stronger cognitive-affective abnormalities in them.

Possible Significance of the Study

“A calorie-reduced diet is the only dietary pattern among those studied that is associated with significantly higher scores for depressive symptoms,” the study states. This finding contrasts with previous randomized controlled trials that suggested low-calorie diets could have a positive effect on depressive symptoms. In those studies, however, comprehensive nutrient intake was ensured.

The new findings suggest that a calorie-reduced diet is the only dietary pattern among those studied that is associated with significantly higher scores for depressive symptoms. Individuals with a high BMI seem particularly at risk for an increase in their depressive symptoms. This could become an important focus for medical care.

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Some pregnant women rely on the Louwen diet.

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Limitations

To confirm the results and subsequently develop tailored dietary recommendations, further research is needed. The study was a retrospective cross-sectional study. Not only are objective dietary data missing, but there are also indications that the NHANES data used may lack objective dietary information. Additionally, the assessment of depressive symptoms relies solely on self-reports.

This article is a machine translation of the original German version of FITBOOK and has been reviewed for accuracy and quality by a native speaker. For feedback, please contact us at info@fitbook.de.