An equally important discovery was that intestinal AMPKα1 knockout mice on chow diet develop adipocyte hypertrophy with a downregulation of the brown fat thermogenic program (i.e., reduced UCP1 expression) and a subsequent reduction in energy expenditure9, that likely resulted in greater obesity upon high fat feeding. The gene discussed is PRKAA1; the disease is obesity due to melanocortin 4 receptor deficiency.