Adoptive transfer of MDSCs (e.g., Gr-1+ cells) into high-fat diet-fed mice improved the response of the recipient mice to insulin while, in contrast, MDSCs depletion (after treatment with anti-Gr-1 antibody) increased their susceptibility to obesity and further worsened their resistance to insulin. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.