INS and obesity due to melanocortin 4 receptor deficiency: Several observations support this possibility: (a) a given amount of glucose is more effective in stimulating secretion when given orally than when administered intravenously (Louis Sylvestre, 1976), which points to the involvement of neural mechanisms superimposed on the humoral; (b) atropine can inhibit the insulin response to ingested glucose, while not affecting the secretory response to infused glucose (Henderson, Jefferys, Jones, & Stanley, 1976); (c) vagotomy suppresses the development of diet‐induced obesity (Sclafani, Aravich, & Landman, 1981).