Obesity in chow-fed p62Δ69-251 mice (Fig. 1a) is primarily the result of increased body fat with only a slight (but significant) increase in lean tissue mass (Fig. 1b), and is accompanied by glucose intolerance (Fig. 1c), elevated fasting levels of insulin (Fig. 1d) and insulin resistance (Fig. 1e). Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.