Time-Restricted Eating and Cancer: Clinical Outcomes, Mechanisms, and Moderators

This study examines whether time-restricted eating — limiting food intake to a specific window of hours each day — improves outcomes and reduces side effects in patients with rectal or breast cancer receiving chemotherapy before surgery. **You may be eligible if:** - You are 18 or older - You have stage II, III, or IV rectal cancer (with curative intent) or HER2-positive or triple-negative breast cancer (stage I–III) - You are currently receiving chemotherapy (neoadjuvant therapy) before surgery and have been on it for no more than 4 weeks - Your BMI is 18.5 or higher **You may NOT be eligible if:** - You have had prior pelvic radiation or prior chemotherapy within 12 months of this cancer diagnosis - You currently eat within a window of less than 10 hours per day (you're already doing it) - You work overnight shifts more than once a week - You are pregnant or breastfeeding - You have serious heart failure, severe neuropathy, or GI problems unrelated to cancer - You have psychiatric or substance use disorders that would interfere with following the eating schedule Talk to your doctor to see if this trial is right for you.