This is well illustrated by Gibbons et al. (2017), who demonstrated recently that individuals with overweight and obesity who lost weight (responders to exercise) after a 12-week supervised aerobic intervention (70% of the individual’s HRmax, five times per week) displayed an elevated postprandial rise in GLP-1 and total PYY, and a greater suppression in acylated ghrelin compared to non-responders (Gibbons et al., 2017). The gene discussed is GHRL; the disease is obesity due to melanocortin 4 receptor deficiency.