Pollution, stress response, and obesity: A systematic review.

Limited literature addresses the association between pollution, stress, and obesity, and knowledge synthesis on the associations between these three topics has yet to be made. Two reviewers independently conducted a systematic review of MEDLINE, Embase, and Web of Science Core Collection databases to identify studies dealing with the effects of semi-volatile organic compounds, pesticides, conservatives, and heavy metals on the psychosocial stress response and adiposity in humans, animals, and cells. The quality of papers and risk assessment were evaluated with ToxRTool, BEES-C instrument score, SYRCLE's risk of bias tool, and CAMARADES checklist. A protocol for the systematic review was registered on PROSPERO. Of 1869 identified references, 63 were eligible after title and abstract screening, 42 after full-text reading, and risk of bias and quality assessment. An important body of evidence shows a positive association between pollution, stress response, and obesity. Pollution stimulates the hypothalamic-pituitary-adrenal axis by activating the glucocorticoid receptor signaling and transcriptional factors responsible for adipocyte differentiation, hyperphagia, and obesity. Endocrine-disrupting chemicals also alter the Peroxisome Proliferator-activated Receptor gamma pathway to promote adipocyte hyperplasia and hypertrophy. However, these associations depend on sex, age, and pollutant type. Our findings evidence that pollution promotes stress, leading to obesity.