Bone mass and lean mass decrease with age and these changes are associated with increased fracture risk and sarcopenia. Previous studies demonstrated that a probiotic mixture of Lacticaseibacillus paracasei DSM13434, Lactiplantibacillus plantarum DSM 15312 and DSM 15313 (L. Mix) prevents bone loss in ovariectomized (ovx) female mice. The purpose of the present study is to test if the beneficial effect of L. Mix is modified by the diet. Female mice were fed either a high-fat (HFD, 60% kcal from fat) or a low-fat (LFD, 10% kcal from fat) diet and subjected to either sham or ovx surgery and treated with L. Mix for 12 weeks. L. Mix treatment increased total body bone mineral density (p ≤ 0.01), by increasing cortical bone area, and total body lean mass (p = 0.035) in mice on LFD but not in mice on HFD. Metagenome sequencing of cecal content showed that L. Mix treatment increased the relative abundance of Lacticaseibacillus paracasei and, Lactiplantibacillus plantarum, demonstrating successful treatment. In addition, the probiotic treatment affected the overall gut microbiota composition and functionality. These findings demonstrate that the L. Mix in combination with a healthy diet is beneficial for musculoskeletal health in female mice.