Introduction: Many people worldwide attempt to lose weight or adopt strategies to control it. Some have resorted to the consumption of commercialized diet pills to achieve this goal. Multiple brands exist without clearly indicating their mechanism of action or adverse effects on human health. This study aims to determine the antibacterial effect of commercial diet pills on members of the intestinal microbiota. Methodology: Commercialized diet pills were bought from a pharmacy in the North of Lebanon. Broth microdilution test was performed to determine the Minimum Inhibitory Concentrations (MICs) of the aqueous suspension against forty-two isolates distributed into four Enterobacterales species. MIC of the digested form was determined against six different strains. GC-MS analysis was performed to elucidate the components of the diet pill compared to the manufacturer's list. Results: Broth microdilution results revealed that MICs of the diet pill aqueous suspension ranged from 3.9x103-9.76x102 µg/mL for Escherichia coli, Enterobacter spp., and Proteus spp. For Klebsiella species, MIC of carbapenem-resistant isolates reached 1.95x103 µg/mL. The digested form had a significantly lower antibacterial effect compared to the aqueous suspension. GC-MS analysis results corresponded with the list of ingredients provided by the manufacturer. Conclusions: The results showed significant antibacterial activity of a commercial diet pill on different members of the human intestinal microbiota regardless of their resistance profile. Further work is needed to elucidate the antibacterial effect of the digested components to accurately understand their effect on the intestinal microflora and thus on human health.