Common Pathways in Depression and Obesity: The Role of Gut Microbiome and Diets

This paper aims to review data regarding two determinants of comorbidity between depression and obesity, i.e., the role of disturbed gut microbiome in their genesis and of diets in their treatment. Obesity and major depressive disorders (MDD) are highly comorbid, the “metabolic” (obese) subtype of MDD affects about one third of all individuals with MDD. There is an urgent need for better therapies strategies, which may include specific dietary measures. A diet low in carbohydrates (low-carb), effective in obesity, may be beneficial also in MDD. However, the underlying mechanisms have not yet been elucidated. Recent data suggest a key role of gut microbiota, neuroplasticity, and neuroinflammation in obesity and MDD. We will focus on the brain-derived neurotrophic factor (BDNF), and microglial fractalkine, a main modulator of neuroinflammation. BDNF and fractalkine may be involved in “metabolic” depression. Future studies may uncover specific pathophysiological pathways in affected patients towards more efficient causal therapies.