Background: Sleeve gastrectomy (SG) has been used for the surgical treatment of morbid obesity as a first or definitive procedure with satisfactory results. The objective of this study in rats was to establish the effects of SG on weight loss depending on the post-surgical type of diet followed. Methods: Thirty male Wistar rats were fed ad libitum during 3 months on a high-fat diet (HFD) to induce obesity. After this first phase, rats were subdivided in three groups of ten rats each and underwent a sham intervention, an SG, or no surgery but were pair-fed to the amount of food eaten by the animals of the SG group. At this time point, half of the animals in each group continued to be fed on the HFD, while the other half was switched to a normal chow diet (ND). Thus, the following subgroups were established: sham-ND, sleeve-ND, pair-fed-ND as well as sham-HFD, sleeve-HFD, and pair-fed-HFD. Body weight and food intake were recorded daily for 4 weeks. The feed efficiency rate (FER) was determined from weekly weight gains and caloric consumption during this period. Results: Statistically significant (P¿<¿0.05) differences in body weight were observed between the six experimental groups after 4 weeks of the interventions with rats in the sleeve-ND group experimenting the highest weight loss (-78.2¿±¿10.3 g) and animals in the pair-fed-HFD group exhibiting the lowest weight reduction (-4.0¿±¿0.1 g). Interestingly, the FER value of rats that underwent the SG and continued to be fed on a HFD was significantly (P¿<¿0.05) lower than that of sham operated and pair-fed animals on the same diet. Conclusion: The positive effects of SG on weight reduction are observed in obese rats submitted to the intervention and subsequently following an ND or even an HFD.