INS and type 2 diabetes mellitus: Thorough studies from Korea and Belgium reported similar reductions in β cell mass in T2D.3,4 Another finding important for understanding T2D is that obese nondiabetic subjects in three studies had only a 20–40% increase in β cell mass compared to lean controls.2,4,5 This only modest increase was surprising, as the increase of β cell mass in insulin resistant mice is proportionally much higher.6