Cancer-associated anorexia, a debilitating condition characterized by progressive appetite loss in oncology patients, contributes to pancytopenia, sarcopenia, and adipose tissue depletion. Megestrol acetate (MA) improves appetite and promotes weight gain through multiple mechanisms, playing a crucial role in the nutritional management of cancer patients. Total mesorectal excision (TME) following neoadjuvant chemotherapy has become the standard treatment strategy for patients with locally advanced colorectal cancer (LACRC). Despite its oncological benefits, neoadjuvant chemotherapy frequently induces grade ≥2 gastrointestinal toxicities (including nausea, emesis, and diarrhea) that exacerbate malnutrition through appetite suppression and negative energy balance. Previous studies have demonstrated that combining MA with first-line maintenance chemotherapy in patients with metastatic colorectal cancer significantly improves appetite, increases body weight, enhances quality of life, and improves prognosis. However, the safety and efficacy of MA during the neoadjuvant treatment phase of LACRC remain unclear. This multicenter, randomized controlled clinical trial aims to evaluate the effects of MA on chemotherapy--related weight loss, anorexia, nutritional status, and chemotherapy tolerance in patients with LACRC undergoing neoadjuvant chemotherapy. Additionally, this study will assess the safety profile of MA in this clinical setting.