Present invention features a method for controlling body weight, comprising Lactobacillus reuteri GMNL-263 with the deposition numbers of BCRC 910452 and CCTCC M 209263. Moreover, the invention also relates to a novel use of the composition or the isolated Lactobacillus strain for controlling body weight, whose mechanism is inhibiting biosynthesis of lipids and reducing formation of lipid droplets so as to control body weight.