PYY and obesity due to melanocortin 4 receptor deficiency: There are many studies which have shown that dietary fiber can prevent obesity by regulating intestinal digestion and absorption, microflora composition, enzyme activity, short-chain fatty acids, and other related receptor (GPCRs, Y2), promoting hormone secretion (PYY, GLP-1, NF-κB) and regulating appetite, metabolism, and immunity through the brain-intestinal axis [26,27,28].