Faldt et al [26] but also Wernstedt et al [13] observed that pre-obese Il6 deficient mice had a higher RER than their WT controls, indicating a preferential oxidation of carbohydrates vs fat, which has been postulated as a mechanism behind the subsequent development of obesity in this mouse model. The gene discussed is IL6; the disease is obesity due to melanocortin 4 receptor deficiency.