The present invention relates to a pharmaceutical composition or a Toona sinensis extract for decreasing weight or body fat, wherein the pharmaceutical of the present invention comprises: 40 to 75 parts by weight of gallic acid 15 to 40 parts by weight of ethyl gallate and 10 to 30 parts by weight of methyl gallate.本發明係有關於一種用於減少體重或降低體脂肪之醫藥組成物或香椿萃取物,其中此醫藥組成物係包括:40至75重量份之沒食子酸;15至40重量份之沒食子酸乙酯;以及10至30重量份之沒食子酸甲酯。