A Systematic Review on the Association between Obesity and Mood Disorders and the Role of Gut Microbiota

Abstract

Obesity is a complex health condition that increases the susceptibility to developing cardiovascular diseases, diabetes, and numerous other metabolic health issues. The effect of obesity is not just limited to the conditions mentioned above; it is also seen to have a profound impact on the patient's mental state, leading to the onset of various mental disorders, particularly mood disorders. Therefore, it is necessary to understand the mechanism underlying the crosstalk between obesity and mental disorders. The gut microbiota is vital in regulating and maintaining host physiology, including metabolism and neuronal circuits. Because of this newly developed understanding of gut microbiota role, here we evaluated the published diverse information to summarize the achievement in the field. In this review, we gave an overview of the association between obesity, mental disorders, and the role of gut microbiota there. Further new guidelines and experimental tools are necessary to understand the microbial contribution to regulate a balanced healthy life.

Keywords: gut–microbiota; mental disorders; metabolites; mood disorders; obesity.

Figure 1

Prisma flowchart depicting the studies selected.

Figure 2

(A) Forest plot between obesity and mood disorders [9,44,45,46,47,48,49,50,51,52,53,54,55]. The box and the horizontal lines represent study specific OR and 95% CI, respectively. The size of the box is an indicator of the weightage of that study. Here, odds ratio greater than 1 suggest the odds of mood disorders are higher in obese people in comparison to normal controls. (B) Funnel plot of obesity and mood disorders for publication bias.

Figure 3

(A) Forest plot between obesity and microbiota [56,57,58,59,60,61,62,63,64,65,66]. The box and the horizontal lines represent study specific OR and 95% CI, respectively. The size of the box is an indicator of the weightage of that particular study. Here, odds ratio less than 1 suggest the relative abundance of Firmicutes is higher in obese people. (B) Funnel plot of obesity and microbiota for publication bias.

Figure 3

(A) Forest plot between obesity and microbiota [56,57,58,59,60,61,62,63,64,65,66]. The box and the horizontal lines represent study specific OR and 95% CI, respectively. The size of the box is an indicator of the weightage of that particular study. Here, odds ratio less than 1 suggest the relative abundance of Firmicutes is higher in obese people. (B) Funnel plot of obesity and microbiota for publication bias.

Figure 4

(A) Forest plot between mood disorders and microbiota [67,68,69,70,71,72,73,74,75,76,77,78,79]. The box and the horizontal lines represent study specific OR and 95% CI, respectively. The size of the box is an indicator of the weightage of that particular study. Here, odds ratio greater than 1 suggest that the relative abundance of Bacteroidetes is higher in people with mood disorders. (B) Funnel plot of mood disorders and microbiota for publication bias.