PLoS Biology brings us more interesting calorie restriction (CR) science - relationships between Sirt1 (the mammalian version of Sir2) and insulin in this case: "Sir2 and insulin/IGF-1 are the major pathways that impinge upon aging in lower organisms. In [roundworms] a possible genetic link between Sir2 and the insulin/IGF-1 pathway has been reported. Here we investigate such a link in mammals. We show that Sirt1 positively regulates insulin secretion in pancreatic [beta] cells. ... In mammals a characteristic set of physiological changes takes place during long-term CR, which overlaps the rapid physiological adaptations to short-term food limitation. One such change is the use of dietary fat or fat mobilized from [white adipose tissue] for energy . Another is a large reduction in blood insulin levels accompanied by an increase in insulin sensitivity, i.e., the ability of insulin to promote glucose utilization."