These conclusions were based on the findings that: (1) the restoration of hematopoietic cells in KitW/Wv mice, whether or not the hematopoietic cells could generate mast cells, led to weight gain when mice were fed a HFD and (2) mice containing an overexpressing Cre recombinase linked to Cpa3, which results in the death of mast cells, are not protected from HFD-induced obesity or insulin resistance. Here, CPA3 is linked to obesity due to melanocortin 4 receptor deficiency.