Inclusion Criteria:

• Presumed newly diagnosed GBM based on imaging findings consistent with GBM on brain MRI (e.g., heterogeneously enhancing mass with central necrosis and surrounding edema), as determined by the treating neuro-oncology team

• Age ≥ 18 years at the time of consent

• Karnofsky performance status (KPS) ≥ 70 at baseline

• Absolute neutrophil count (ANC) ≥ 1.5 × 10^9/L

• Platelet count ≥ 100 × 10^9/L

• Hemoglobin ≥ 9 g/dL

• Serum creatinine ≤ 1.5 × upper limit of normal (ULN) or creatinine clearance ≥ 60 mL/min

• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN

• Total bilirubin ≤ 1.5 × ULN

• Willingness and ability to comply with CGM device use and attend dietary counseling sessions as part of the study protocol

Exclusion Criteria:

• Recurrent glioblastoma or prior therapy for glioblastoma beyond surgical resection or biopsy

• History of eating disorders (e.g., anorexia nervosa, bulimia) or substance use disorder within the past 12 months

• Any other uncontrolled or inadequately managed medical illness (e.g., unstable cardiovascular, hepatic, renal, or psychiatric condition) that, in the opinion of the investigator, would interfere with study participation or interpretation of results

• Concurrent diagnosis of another active malignancy requiring treatment

• Pregnancy or breastfeeding at the time of enrollment

• Documented history of type 1 diabetes mellitus

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 05/12/2026. Questions regarding updates should be directed to the study team contact.