Background <p>Anorexia nervosa (AN) often requires nutritional rehabilitation including nasogastric feeding. However, achieving shared treatment goals between clinicians, patients, and families can be challenging. Weight prediction can be a valuable tool in this process; however, conventional approaches rely largely on clinical experience and lack precision. We therefore developed a simplified calorie-based weight prediction model grounded in the revised Harris–Benedict equation.</p> Case presentation <p>This case report describes the clinical application of this model in a woman in her twenties with AN. By visualizing predicted weight trajectories under different caloric intake strategies, the model facilitated consensus building between the patient, her family, and the treatment team, leading to the acceptance of nasogastric feeding and structured behavioral therapy.</p> Conclusions <p>The present case may suggest the potential utility of a calorie-based weight prediction model as a dynamic, noninvasive, and quantitative tool for inpatient management of AN. While the approach could facilitate understanding and agreement regarding treatment for AN, further evaluation in larger cohorts is required to assess accuracy and clinical impact.</p>