SIRT1 and obesity due to melanocortin 4 receptor deficiency: If STACs such as resveratrol and SRT1720 increase mitochondrial function and protect against obesity by directly activating Sirt1, it is reasonable to predict that transgenic mice with increased expression of Sirt1 from its native promoter (gain of function) will have increased mitochondrial function and be protected against obesity (Banks et al., 2008, Boutant et al., 2016, Pfluger et al., 2008).