Depression and obesity are common conditions with major public health implications that tend to co-occur within individuals. The relationship between these conditions is bidirectional: the presence of one increases the risk for developing the other. It has thus become crucial to gain a better understanding of the mechanisms responsible for the intertwined downward physiological spirals associated with both conditions. The present review focuses specifically on shared biological pathways that may mechanistically explain the depression–obesity link, including genetics, alterations in systems involved in homeostatic adjustments (HPA axis, immuno-inflammatory activation, neuroendocrine regulators of energy metabolism including leptin and insulin, and microbiome) and brain circuitries integrating homeostatic and mood regulatory responses. Furthermore, the review addresses interventional opportunities and questions to be answered by future research that will enable a comprehensive characterization and targeting of the biological links between depression and obesity.

Depression and obesity: evidence of shared biological mechanisms

The field of nutritional psychiatry has generated observational and efficacy data supporting a role for healthy dietary patterns in depression onset and symptom management. To guide future clinical trials and targeted dietary therapies, this review provides an overview of what is currently known regarding underlying mechanisms of action by which diet may influence mental and brain health. The mechanisms of action associating diet with health outcomes are complex, multifaceted, interacting, and not restricted to any one biological pathway. Numerous pathways were identified through which diet could plausibly affect mental health. These include modulation of pathways involved in inflammation, oxidative stress, epigenetics, mitochondrial dysfunction, the gut microbiota, tryptophan-kynurenine metabolism, the HPA axis, neurogenesis and BDNF, epigenetics, and obesity. However, the nascent nature of the nutritional psychiatry field to date means that the existing literature identified in this review is largely comprised of preclinical animal studies. To fully identify and elucidate complex mechanisms of action, intervention studies that assess markers related to these pathways within clinically diagnosed human populations are needed.

Diet and depression: exploring the biological mechanisms of action

Depression Heterogeneity and Its Biological Underpinnings: Toward Immunometabolic Depression

Objective Food security has been suggested to be a risk factor for depression, stress and anxiety. We therefore undertook a systematic review and meta-analysis of available publications to examine these associations further. Design Relevant studies were identified by searching Web of Science, Embase, Scopus and PubMed databases up to January 2019. Setting OR was pooled using a random-effects model. Standard methods were used for assessment of heterogeneity and publication bias. Participants Data were available from nineteen studies with 372 143 individual participants from ten different countries that were pooled for the meta-analysis. Results The results showed there was a positive relationship between food insecurity (FI) and risk of depression (OR = 1·40; 95 % CI: 1·30, 1·58) and stress (OR = 1·34; 95 % CI: 1·24, 1·44) but not anxiety. Subgroup analysis by age showed that subjects older than ≥65 years exhibited a higher risk of depression (OR = 1·75; 95 % CI: 1·20, 2·56) than younger participants (OR = 1·34; 95 % CI: 1·20, 1·50), as well as a greater risk of depression in men (OR = 1·42; 95 % CI: 1·17, 1·72) than women (OR = 1·30; 95 % CI: 1·16, 1·46). Finally, subgroup analysis according to geographical location illustrated that food insecure households living in North America had the highest risk of stress and anxiety. Conclusions The evidence from this meta-analysis suggests that FI has a significant effect on the likelihood of being stressed or depressed. This indicates that health care services, which alleviate FI, would also promote holistic well-being in adults.

/pdf/food-insecurity-and-mental-health-a-systematic-review-and-44jp8rzh26.pdf

Food insecurity and mental health: a systematic review and meta-analysis.

http://www.scielo.br/pdf/rbp/v42n6/1516-4446-rbp-1516444620190650.pdf

Prevalence and correlates of major depressive disorder: a systematic review.

BackgroundThe association between body size, weight change and depression has not been systematically summarised, especially for individuals who are underweight.AimsTo conduct a systematic review and a meta-analysis to examine the association between indices of body size, weight change and depression.MethodA total of 183 studies were selected. Fully adjusted hazard ratios (HRs) or odds ratios (ORs) were extracted. A total of 76 studies contributed to data synthesis with a random-effect model, and subgroup analyses were conducted to evaluate the effect of potential moderators.ResultsIn cohort studies, underweight at baseline increased the risk of subsequent depression (OR = 1.16, 95% CI 1.08-1.24). Overweight (BMI 25-29.9 kg/m2) showed no statistically significant relationship with depression overall; however, the subgroup analyses found different results according to gender (men: OR = 0.84, 95% CI 0.72-0.97, women: OR = 1.16, 95% CI 1.07-1.25). In cross-sectional designs, obesity with BMI >40 kg/m2 showed a greater pooled odds ratio than obesity with BMI >30 kg/m2ConclusionsBoth underweight and obesity increase the risk of depression. The association between overweight and depression differs by gender.

/pdf/association-between-body-size-weight-change-and-depression-4ncd3ykqp0.pdf

Seokhun Jeong

Papers

Association between body size, weight change and depression: systematic review and meta-analysis