AbstractPurposeA healthy lifestyle after colorectal cancer (CRC) diagnosis may improve prognosis. Data related to lifestyle change in CRC survivors are inconsistent and potential interrelated changes are unknown.MethodsWe assessed dietary intake, physical activity, body mass index (BMI), waist circumference, and smoking among 1072 patients diagnosed with stages I–III CRC at diagnosis, 6 months and 2 years post-diagnosis. An overall lifestyle score was constructed based on the 2018 World Cancer Research Fund/American Institute of Cancer Research recommendations (range 0–7). We used linear mixed models to analyze changes in lifestyle over time.ResultsParticipants had a mean (± SD) age of 65 ± 9 years and 43% had stage III disease. In the 2 years following CRC diagnosis, largest changes were noted for sugary drinks (− 45 g/day) and red and processed meat intake (− 62 g/week). BMI (+ 0.4 kg/m²), waist circumference (+ 2 cm), and dietary fiber intake (− 1 g/day) changed slightly. CRC survivors did not statistically significant change their mean intake of fruits and vegetables, alcohol, or ultra-processed foods nor did they change their physical activity or smoking behavior. Half of participants made simultaneous changes that resulted in improved concordance with one component as well as deteriorated concordance with another component of the lifestyle score. Overall lifestyle score changed from a mean 3.4 ± 0.9 at diagnosis to 3.5 ± 0.9 2 years post-diagnosis.ConclusionsCRC survivors hardly improve their overall lifestyle after diagnosis.Implications for Cancer SurvivorsGiven the importance of a healthy lifestyle, strategies to effectively support behavior changes in CRC survivors need to be identified.