| Abstract | Background and aims:
There is evidence to suggest that a ketogenic diet (KD) may help to alleviate psychiatric symptoms, including depression, but this has not been studied extensively or compared directly to the impact of the more common low carbohydrate diet (LCD). The aim of this research was to understand the impact of a non-calorie-restricted low carbohydrate diet and ketogenic diet on depression and aspects of psychological well-being in those with either mild to moderate depressive symptoms or low or no depressive symptoms. Materials and methods:
In a randomised control trial with quasi experimental design, participants with mild to moderate depressive symptoms and low depressive symptoms were randomised into either a LCD, a KD, or a control diet (diet as usual) generating a total of 6 participant groups. The dietary interventions (LCD and KD) were delivered through an online education platform for 12 weeks, followed by 12 weeks of unsupported continued diet. The control diet was maintained for a total of 6 weeks. Examinations at baseline (T0), day 1, week 6, week 12, and week 24 included questionnaires and psychological measures stress, anxiety, mental wellbeing, positive and negative affect, depression, self-compassion, social support, and body appreciation. Demographical data was also collected and analysed. Attrition rates were explored post intervention, and a qualitative thematic analysis was carried out on participants interview data following the KD to better understand their experience of the dietary intervention. Results:
From study 1, the KD group saw no improvements in psychological wellbeing. The LCD group reported significant improvements in stress, anxiety, and negative affect after 12 weeks and in depressive symptoms after 24 weeks compared to the KD and control group. Significant improvements in positive affect, mental well-being and depressive symptoms were found in those with lower levels of body appreciation compared to those with higher levels, regardless of diet type. From study 2, dropout rates peaked during the 12-week intervention compared to post intervention and the end of the study at 24 weeks. Those with depressive symptoms were less likely to drop out of the study compared to those who were ‘healthy’. From the qualitative study 3, participants in the KD group experienced both physical and mental health improvements. They lost weight and experienced an increase in confidence, energy, and self-esteem. Some reported a renewed meaning and purpose in life. Conclusion:
The ketogenic diet did not improve quantitatively measured depressive symptoms or aspects of psychological well-being from self-reported questionnaires. However, from interview data, improvements were experienced by those on the ketogenic diet suggesting that the diet worked for some. Reasons for this contradiction are explored and may be explained in part, by reviewing the intervention design. A low carbohydrate diet was found to improve some aspects of psychological well-being in those with mild to moderate depressive symptoms over 24 weeks. Adverse events experienced were mild and temporary, but retention of participants was challenging. Further well-designed randomised control trials are warranted to identify whether a ketogenic diet would improve psychological well-being in those with more severe depression akin to antidepressant efficacy. |
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