compared mitochondrial enzymatic function of circulating lymphocytes from subjects with normal weight and obesity ranging in age from 17 to 75 years and found decreased activities of cytochrome oxidase and citrate synthase in lymphocytes from subjects with obesity, with the greatest decrease in the youngest (<45 years) and oldest (>65 years) subjects.19 Here, CS is linked to obesity due to melanocortin 4 receptor deficiency.