To date, gut microorganisms showed the ability to decrease body weight, leptin levels, abdominal and epididymal fat volume, to down-regulate lipogenic genes and even to counteract Enterobacter-induced obesity (Enterobacter cloacae B29) and further, to restore the beneficial proportion of different bacterial taxa [29,30,31,32,33,34]. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.