Studies using non-pregnant animal models of obesity and diabetes have demonstrated that the inclusion of butyrate and propionate in the diet leads to reduced body weight, obesity, fasting glucose and insulin levels, improved insulin tolerance, and amelioration of diabetes symptoms (Gao et al., 2009; Henagan et al., 2015) (Figure 4). This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.