GHRL and Anorexia: Whereas physical exercise may cause anorexia and weight loss by decreasing plasma levels of ghrelin and/or increasing levels of BDNF, GDF15, GLP-1, and other gut-derived hormones, the effects are usually transient and only associated with weight loss when the exercise is sufficiently taxing to create an energy loss that exceeds energy intake; this may require achieving a VO2peak of at least 60% for a protracted period of time (Broom et al., 2017)—goals seldom achieved in morbidly obese individuals.