Interestingly, we observed, by proteomics analysis of fasting plasma obtained from men with obesity and also from mice, that after six weeks consumption of an eucaloric high-fat diet (64E% fat) enriched in either unsaturated or saturated fatty acids (FAs), apolipoprotein A-IV (apoA-IV) was the circulating protein exhibiting the most significant increase [6]. The gene discussed is APOA4; the disease is obesity due to melanocortin 4 receptor deficiency.