Colorectal cancer patients account for the largest proportion of total cancer patients in Japan. With an increase in its surgical cases and relatively higher five-year survival rate, the number of cancer survivors is expected to be increasing. Therefore, primary prevention, surgical therapy and recurrence prevention for colorectal cancer are public health priorities in Japan. General and abdominal obesity (Not only abdominal but also general obesity) are risk factors for colorectal cancer. In addition, accumulated abdominal fat can extend time spent in surgery by hindering operative procedures and surgical field expansion. These factors raise the risk of postoperative complications such as bleeding and surgical site infection, which eventually leads to increased medical expenses. Physical activity is one of protective factors for colorectal cancer. Recent studies showed that exercise intervention in cancer survivors reduces the cancer recurrence risk. Furthermore, it has been suggested that exercise interventions are effective in reducing fatigue, improving immune function, and maintaining physical function. However, the effectiveness of preoperative exercise intervention aimed at reducing weight in colorectal cancer patients remains unknown. In this review article, we discuss necessity for peri-operative weight loss among obese colorectal cancer patients.