The mechanism of weight change in PD is considered multifactorial in relation to the various stages of the disease; moreover, physiological parameters such as neuroendocrine influences (such as orexin, ghrelin, and leptin), motivation and rewarding, hunger and satiation [38], apathy, fatigue and gustatory/olfactory deficits may influence weight and/or eating behavior. The gene discussed is HCRT; the disease is Parkinson disease.