Here's a study confirming that sirtuins are indeed overexpressed during the practice of calorie restriction in humans. That should please the resveratrol brigade: "Sirtuins may provide novel targets for treating some diseases associated with oxidative stress, such as obesity and its comorbidities. However, there are a few in vivo studies in humans about the potential role of sirtuins as therapeutic targets among obese patients undergoing caloric restriction. ... Gene expression of two sirtuins (SIRT1 and SIRT2) [of] obese subjects [before] and following an 8-week hypocaloric diet was investigated. ... The intervention up-regulated the expression of both sirtuins ... SIRT1 and SIRT2 may serve as key regulators for some obesity comorbidities related to antioxidant status." The more interesting question is whether these effects occur for people of a more reasonable weight range.

Link: http://www.ncbi.nlm.nih.gov/pubmed/18837744