The antonyms for the word "buffed up" can be defined as weak, slim, scrawny, and feeble. These terms are used to describe physical appearance and lack of strength or muscular build. While "buffed up" suggests a toned and muscular body, its opposite portrays a frail and thin person. People who have not worked out or trained their bodies tend to have these traits. In contrast, athletes and bodybuilders strive to achieve a buffed-up physique through intense workouts and a balanced diet. Therefore, the antonyms of "buffed up" describe the opposite of a strong, muscular, and toned body.