The present invention relates to a composition containing alpha-lipoic acid and N-acetylcysteine as active ingredients. The mixture composition of alpha-lipoic acid and N-acetylcysteine of the present invention reduces the risk of side effects caused by drugs and has an excellent effect of suppressing weight gain compared with each single composition containing alpha-lipoic acid or N-acetylcysteine, due to the synergistic effect resulting from the combined administration of the two drugs, and thus the composition of the present invention can be favorably used for the prevention or treatment of obesity.