Display omitted •There are no significant differences between the administration of viable or inactive L. rhamnosus GG on metabolic parameters.•The supplementation with L. rhamnosus GG, viable or inactive, is able to control the weight gain and accumulation of visceral fat from HFHF diet consumption.•The use of inactivated L. rhamnosus GG is more effective on the modulation of bacterial species of the gut microbiota.•The interaction between L. rhamnosus and Blautia glucerasea attenuates some adverse metabolic effects resulting from the HFHF diet. High-fat High-fructose diets have been associated with metabolic disorders and gut microbiota dysbiosis. Thus, the administration of probiotic or postbiotic from the strain Lacticaseibacillus rhamnosus GG has been investigated as a protective strategy. The aim of this study was to analyze the impact of L. rhamnosus GG administration in rodents fed a high-fat high-fructose diet. Male Wistar rats with oral supplementation of L. rhamnosus GG, viable or heat-inactivated, for 6 weeks were evaluated for somatic measurements, food and energy intake, biochemical markers, and gut microbiota. The daily administration of L. rhamnosus GG, as probiotic or postbiotic, was beneficial in attenuating weight gain, visceral fat deposition and visceral hypertriglyceridemic phenotype. Furthermore, the administration of heat-inactivated L. rhamnosus GG elicited an increase of species such as Akkermansia muciniphila, Blautia glucerasea, Sarcina maxima and L. rhamnosus, where the interaction between L. rhamnosus and Blautia glucerasea attenuated metabolic markers altered by the obesogenic diet.