overweight people has shown the excellent safety of this bacteria. health benefits hafnia produces a protein called caseinolytic protease b (clpb) which has been shown to be a mimetic of the hormone α-msh which is implicated in the satiety. some enterobacterales bacteria, such as hafnia alvei have been shown to naturally regulate the appetite. more specifically, the hafnia alvei ha4597 strain was tested in ob/ob and high-fat diet-fed obese and overweight mice after administration by gavage. in those two models, the hafnia alvei strain showed good tolerance, reduced body weight gain and fat mass in both obesity models, and a significant decrease in food intake in ob/ob mice. another study describing the administration of the ha4597 strain to high-fat-diet-fed hyperphagic ob/ob male mice, showed a significant decrease (compared to untreated or orlistat-treated mice) in body weight, body fat and food intake but also in treated mice a decrease in blood sugar level, total plasma cholesterol and alanine aminotransaminase. in 2021, the results of a 12-week clinical study comparing oral intake of strain ha45597 versus placebo, were published in the scientific journal nutrients. this prospective, multicenter, double-blind, placebo-controlled and randomized study in 236 overweight volunteers (bmi between 25 and 29.9 kg/m2) clinically confirmed the preclinical data. the primary efficacy endpoint "weight loss" was met: a statistically significant difference was observed in favor of the hafnia alvei group in the proportion of subjects who lost at least 3% of their body weight at 12 weeks (57,7% in the hafnia group versus 41,7% placebo group, p=0,028). among the secondary endpoints achieved, a statistically significant increase in the feeling of satiety was noticed. in addition, the effect of the strain is also greater than the placebo in reducing hip circumference. only hafnia alvei ha4597 had an effect on the cholesterol level and induced a reduction in blood sugar levels. the scientific journal, nature, recently qualified the strain hafnia alvei ha4597, as a "precision probiotic", that is to say a probiotic whose strain and mechanism of action are fully described and understood scientifically. targedys, a french company, which demonstrated that the hafnia alvei ha4597 strain could stimulate satiety via the clpb protein and help to naturally control appetite and lose weight, conducted the studies enabling the marketing of this probiotic. regulatory status hafnia alvei is a food grade bacteria. it is not listed in the novel food catalogue of the european commission. it is listed on the danish list of notified microbial cultures applied in food. hafnia alvei is part of the idf positive list (international dairy federation) of microbial food cultures (mfc) demonstrating safety requirements in fermented food products for worldwide use. it is also classified as a natural health product in the canadian nnhpd (natural and non-prescription health products directorate). the h. alvei ha4597 strain is now marketed in france as a dietary supplement associated with zinc and chromium under the names enterosatys (targedys) and symbiosys satylia chromium and zinc by the laboratory (biocodex), as well as with guarana and chromium under the name of enterosatys weight management. it is also distributed in portugal (symbiosys satylia), italy (satilia), croatia (enterosatys), turkey (satylia), and germany (symbiolife satylia).