NPY and obesity due to melanocortin 4 receptor deficiency: A recent review highlighted four different mechanisms that stress can be linked to overweight and obesity including: (1) cognitive processes such as self-regulation; (2) behavioural effect through inducing overeating, shortening of sleep and decreasing physical activity; (3) physiological changes in the hypothalamic–pituitary–adrenal axis and (4) stimulating the production of biochemical hormones and peptides such as leptin, ghrelin and neuropeptide Y(52).