As speculation, we looked at the expression data of HIF3A by Gene Expression Profiling Interactive Analysis (GEPIA) in cancers mostly associated to obesity (breast, oesophageal, pancreatic, stomach, thyroid, and uterine cancers): HIF3A is significantly downregulated in tumor vs. normal tissue and the promoter regions are methylated (Supplementary Figure S3A), suggesting a causal correlation between methylation of HIF3a in obese patients that subsequently develop cancer. This evidence concerns the gene HIF3A and obesity due to melanocortin 4 receptor deficiency.