Hospital malnutrition is a detrimental prognostic factor regarding hospital mortality, complications, and length of stay. However, the role of hospitalization itself on nutritional status has not been fully elucidated. We report the results of a secondary analysis from the dataset of a recent cross-sectional study at Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. Data from patients evaluated at admission and discharge were collected and compared. One hundred thirty-nine patients were evaluated. Mean length of stay was 13.6 (± 7.7) days. Patients at risk of malnutrition, according to NRS-2002, were 75 (53.9%), while 63 (45.3%) were malnourished according to ESPEN Criteria. Compared to admission, at discharge, patients reported a significant decrease in Mid-Upper Arm Circumference (MUAC)-from 26.5 cm (± 3.6) to 25.9 cm (± 3.7) (p = 0.016), a reduction in Phase angle (PhA)-from 4.25° (± 1.20) to 4.01° (± 1.15) (p = 0.005), fat-free mass (FFM)-from 47.5 kg (± 9.19) to 44.9 kg (± 9.4) (p = 0.03) and fat-free mass index (FFMI)-from 16.9 kg/m2 (± 2.3) to 15.8 kg/m2 (± 2.7) (p = 0.04). Laboratory data showed a reduction of albumin-from 29.2 (± 5.7) to 28.0 (± 5.9) (p = 0.01) and Onodera's PNI- from 29.1 (± 5.6) to 27.6 kg (± 5.6) (p = 0.039). At the multivariate linear regression analysis, the variables significantly associated with a worsening of PhA at discharge are the PhA value at admission and the diagnosis of malnutrition according to ESPEN Criteria. Hospitalization leads to significative changes in nutritional status. A clinical concern should be raised about the quality of hospital food and meal times and on the need for a clinical nutritionist on the ward.