Hyperpolarized 13C MRS following an intravenous bolus injection of [1‐13C]pyruvate (Figure 1I) revealed that obesity was associated with a 40% reduction in the rate of 13C label incorporation into [13C]bicarbonate (i.e., PDH flux) compared with controls (Figure 1J). The gene discussed is PDP1; the disease is obesity due to melanocortin 4 receptor deficiency.