We have recently demonstrated that a Hafnia alvei (H. alvei) HA4597TM strain of commensal bacteria of the Hafniaceae family (formerly Enterobacteriaceae) belonging to the order of Enterobacteriales displays anti-obesity properties in two animal models of obesity, standard-diet-fed leptin-deficient ob/ob and high-fat-diet (HFD)-fed wild-type (WT) mice [11]. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.