The TCF7L2 gene, which is known to play an important role in the transcription of the proglucagon gene and hence the synthesis of glucagon-like-peptide 1 (GLP-1), which is implicated in insulin regulation, appetite and food intake [44,45], has been studied much less in the context of obesity and more in diabetes and metabolic syndrome [46,47]. This evidence concerns the gene GCG and diabetes mellitus.