We confirmed the expected obesity-associated drop in plasma ghrelin in 14-week-old ad libitum–fed mice with diet-induced obesity, which had approximately 38% lower levels than 10- to 12-week-old standard chow–fed WT mice (those mice from Figure 1); ghrelin was undetectable in GKO mice regardless of diet (Figure 5A). This evidence concerns the gene GHRL and obesity due to melanocortin 4 receptor deficiency.