Low Energy and Protein Intake in Brain Tumor Patients Despite Higher Adiposity: A Comparative Study with Gastrointestinal Cancer

Background/Objectives: Nutritional therapy is an essential part of oncologic care, yet patients with brain tumors—especially those with glioblastoma—remain underserved by disease-specific dietary guidelines. This cross-sectional study compares energy and macronutrient intake, as well as body composition, between brain tumor patients, including a glioblastoma subgroup, and patients with gastrointestinal (GI) cancer. Methods: A total of 95 brain tumor patients and 109 GI cancer patients completed standardized three-day estimated food records and underwent bioelectrical impedance analysis and hand-grip strength measurements. Anthropometric parameters, as well as energy and macronutrient intake, were compared between groups. Results: Energy intake was lower in brain tumor patients compared with GI cancer patients (22.8 kcal/kg/day vs. 31.2 kcal/kg/day), as were protein (1.01 g/kg/day vs. 1.34 g/kg/day) and carbohydrates (182.8 g/day vs. 246.8 g/day; all p < 0.01). Despite the lower intake, brain tumor patients exhibited higher BMI scores, body fat percentages, and visceral fat levels (p < 0.05), while fat-free mass and skeletal muscle mass were comparable between groups. The phase angle was higher in brain tumor patients (p = 0.002), whereas the ECW/TBW ratio was lower (p = 0.003). In the glioblastoma subgroup, protein intake did not differ significantly compared with the GI cancer group. However, carbohydrate intake (190.9 g/day vs. 246.8 g/day; p = 0.01), as well as energy intake (25.7 kcal/kg/day vs. 31.2 kcal/kg/day; p = 0.05), remained significantly lower. Conclusions: Brain tumor patients were found to have energy intake levels below ESPEN recommendations for cancer patients (25–30 kcal/kg/day), and their protein intake was at the lower ESPEN threshold (1.0 g/kg/day), coupled with increased adipose tissue. The observed caloric deficit was accompanied by reduced carbohydrate intake, particularly in the glioblastoma subgroup. These findings highlight the need for individualized nutritional approaches in neuro-oncology. Until disease-specific recommendations are available, general dietary guidelines such as those by ESPEN offer a pragmatic interim orientation.