Now, in eLife, Sona Kang, Evan Rosen and colleagues in the USA, Denmark and Sweden – including Dongjoo You of the University of California Berkeley as first author – report how a key epigenetic regulator called Dnmt3a contributes to obesity-related insulin resistance (You et al., 2017). The gene discussed is DNMT3A; the disease is obesity due to melanocortin 4 receptor deficiency.