Calorie restriction and low-fat diets may reduce depression in individuals with higher cardiometabolic risk

1. In this systematic review and meta-analysis, calorie restriction and low-fat diets were associated with small improvements in depressive symptoms among individuals at elevated cardiometabolic risk.

2. However, evidence for other dietary interventions such as Mediterranean-style diets was limited, as were comparisons to first-line treatments such as antidepressant medications.

Evidence Rating Level: 1 (Excellent)

Study Rundown: There has been increased interest in dietary interventions as an alternative therapeutic method for individuals with depression or anxiety, particularly those without adequate access to psychotherapy or pharmacotherapy. However, the current literature surrounding dietary interventions has been insufficient to assess longer-term effects. This systematic review aimed to examine the long-term impact of dietary interventions compared with active interventions or no specific diet advice on depression and anxiety. Calorie restriction was shown to potentially reduce symptoms of depression compared with usual care, although its effect on anxiety and quality of life (QoL) was uncertain. When compared with exercise, there was no clear evidence that calorie restriction reduced symptoms of both depression or anxiety or QoL.  Among adults with higher cardiometabolic risk, a low-fat diet was associated with slightly lower depressive symptoms and improved QoL compared with no specific diet advice, but its effect on anxiety was uncertain; when compared with active dietary interventions, a low-fat diet was associated with reduced anxiety symptoms, although any effect on depressive symptoms was uncertain. Comparing a Mediterranean-style diet with no specific dietary advice or active dietary interventions did not produce any certain evidence of effect on depressive symptoms or anxiety in adults with high cardiometabolic risk or adults with pre-existing depression and/or anxiety. Finally, dietary intensive treatment also did not show any certain evidence of effect on depression and QoL compared with no specific dietary advice in adults with malnutrition or cancer. The power of this study was limited by the low quality of evidence and the high heterogeneity of populations and intervention types studied. Nevertheless, this study suggested that specific dietary interventions may have positive effects on mental health outcomes among patients with depression or anxiety.

Click to read the study in AIM

Relevant Reading: The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials

In-Depth [systematic review and meta-analysis]: This systematic review and meta-analysis aimed to assess the effect of dietary interventions on depression and anxiety. Studies were included if they were randomized controlled trials (RCTs) that involved adults aged 18 years and older and explored the effect of dietary interventions compared with active interventions (such as medications or exercise) or no specific diet advice on depression and anxiety. In all, 25 RCTs were included, yielding a study population of 57,726 participants, with a median of 152 participants (interquartile range [IQR], 70 to 341 participants) per RCT. Women made up 62% of this population, and the average age was 53 years. Most of the RCTs were deemed to have high risk of bias (n = 23; 92%), largely due to measurement bias and missing data. Calorie restriction compared with no specific dietary advice in patients with higher cardiometabolic risk was investigated for effect on depression and anxiety in 6 RCTs and on QoL in 3 RCTs. Calorie restriction reduced depressive symptoms (standardized mean difference [SMD], -0.23 [95% CI, -0.38 to -0.09]), but had no apparent effect on anxiety (SMD, -0.10 [95% CI, -0.26 to -0.06]) and QoL (SMD, 0.20 [95% CI, -0.09 to 0.50]). Low-fat diet was investigated for effect on depression in 5 RCTs, on anxiety in 4 RCTs, and QoL in 3 RCTs, and was found to improve symptoms of depression (SMD, -0.03 [95% CI, -0.04 to -0.01]) and QoL (SMD, 0.11 [95% CI, 0.03 to 0.19]). Compared with active dietary interventions, low-fat diet was shown to lower anxiety (SMD, -0.40 [95% CI, -0.68 to -0.11]) but not depression (SMD, -0.18 [95% CI, -0.41 to 0.06]). Among adults with pre-existing depression and/or anxiety, Mediterranean-style diet was investigated for effect on depression in 5 RCTs and on anxiety and QoL in 3 RCTs. Overall, Mediterranean-style diets had little effect on depressive symptoms, anxiety, and QoL, but effect sizes were larger among adults with pre-existing depression and/or anxiety (SMD, -0.55 [95% CI, -1.06 to -0.04]) and in RCTs with an average participant age below 60 years (SMD, -0.54 [95% CI, -0.97 to -0.12]). Overall, this study suggested that specific dietary changes may reduce depressive symptoms in individuals with higher cardiometabolic risk.

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