The human body consists of fat mass and fat-free mass. Most people assume that the higher the body mass index value, the higher the fat level is in a person's body. Sit-ups are movements that rely on the hips and buttocks with the knees raised and performed repeatedly. This study aims to determine whether sit-up exercise has effects on body fat percentage. This research was conducted in the form of a literature review, which is explaining and discussing the topic by taking the material from various literatures such as books, journals, papers and so on. The results of the research of Todingan et al and Meriawati et al on the fat percentage with the sit-up method, a significant decrease in the body fat percentage was found. Whereas in a research conducted by Tendean et al on exercise with Zumba, there was a decrease in the fat percentage from 39.300% to 39.031%. Similar to what Santika did to subjects with jogging and walking exercises, there was a decrease in the fat percentage by 3.8% in jogging exercise and 0.6% in walking exercise. In conclusion, doing sit-ups besides building muscles in the abdomen, doing sit-ups can also reduce the diameter of fat in the abdomen.