As well, increased systemic lipolysis through increased expression of fasting induced adipocyte factor (FIAF), an intestinal lipoprotein lipase (LPL) inhibitor which results predominantly from decreased extraction of energy from the diet [7], may play a role in the protection from obesity in GF mice, although the role of FIAF in the relationship between gut colonization and adiposity has been recently disputed (see [9]). The gene discussed is LPL; the disease is obesity due to melanocortin 4 receptor deficiency.