Following sterilization, the cat's behaviour and feeding rate are modified, leading to a direct risk of increasing the rate of obesity and feline low urinary tract diseases. Some companies which specialize in pet nutrition have produced some formulae adapted to the characteristics of neutered cats, aiming to minimize the negative effects of sterilization. This analytical, exploratory and retrospective study compared the state of health and level of obesity of neutered cats according to the type of food which the animals had been given. Two sets of pets both fed on food sold in veterinary clinics were compared. The first set was fed with a diet from the Neutered Cat (Royal Canin, 61 questionnaires filled in at the end of study), whereas the second set was fed with other veterinary foods (69 questionnaires). An insignificant difference was noted among the 2 sets, taking into account the characteristics of the cats or their owners. However, the results covering various health aspects showed significant differences (p<0.05) such as a protective effect of studied food, for example on obesity (p=0.03; RR=0.7 [0.51-0.97]), disease after neutering (p=0.02; RR=0.63 [0.42-0.94]) gum recession (p=0.08); RR=0.78 [0.59-1.04] or urinary problems (p=0.004); RR=0.21 [0.08-0.56]. Biases were discussed, mainly due to self selection of owners who accepted or not to participate in the study, or a cluster effect due to limited number of veterinary clinics. The design of the next study would have to deal with these aspects.