BackgroundWomen are predisposed to develop intolerance to cancer chemotherapy. Sarcopenia and chemotherapy are mutually related. Women are generally intolerable to chemotherapeutics such as 5-fluorouracil. Although adjuvant oxaliplatin-based chemotherapy, e.g. CAPOX is commonly used to treat colorectal cancer, its effects on patients in terms of sarcopenia and sex remain unknown. We investigated sex disparities in the impacts of CAPOX on body composition in this study.MethodsWe conducted a prospective study on diagnostic metrics used for sarcopenia in colorectal cancer patients receiving adjuvant CAPOX. Evaluations of the nutritional status by the Mini-Nutritional Assessment (MNA), gait speed, grip strength, skeletal muscle mass, fat mass, and bone mineral content using a body composition analyzer were performed in the first, fourth, and eighth cycles of CAPOX (first, second, and third measurements, respectively).ResultsAmong 80 eligible patients, 61 completed four CAPOX cycles. The median differences in MNA, gait, grip strength, muscle mass, fat mass, and bone mineral content between the first and second measurements for men (n = 35) and women (n = 26) were + 10.5% and + 2.9% (p = 0.067), + 4.5% and − 2.6% (p = 0.16), + 1.8% and + 2.8% (p = 0.66), + 2.7% and + 1.3% (p = 0.021), + 4.5% and + 3.5% (p = 0.59), and + 3.3% and + 0.0% (p = 0.006), There were no sex differences in comparisons of the above metrics between the first and third measurements in 34 patients who completed eight CAPOX cycles (19 wen and 15 women).ConclusionsEarly cycles of adjuvant CAPOX may have a negative impact on the postoperative recovery of several metrics for diagnosing sarcopenia in women.