The purpose of this study is to learn the effects of fasting on cancer cells while you get maintenance treatment.

Cancer cells use an increased supply of glucose to make energy and do not have protection against fasting that normal cells do. Because of this, researchers would like to study how fasting may help immunotherapy target cancer cells. Initial studies suggest that fasting may decrease the side effects of immunotherapy and increase the chances of your cancer responding to the immunotherapy. Patient populations will have non-small cell lung cancer in which pembrolizumab have been recommended to treat the cancer as part of standard care

Inclusion Criteria:

• 18 years at the time of informed consent
• Ability to provide written informed consent and HIPAA authorization.
• Eastern cooperative group (ECOG) performance status of 0 to 2
• Newly diagnosed histologically or cytologically confirmed stage IV Non-Small Cell Lung Cancer (NSCLC). Patients with locally advanced NSCLC that are not candidates for definitive therapy but are candidates for trial are allowed per investigator discretion.
• BMI 19 kg/m2
• Patients should be enrolled prior to starting standard of care immunotherapy for the treatment of stage IV NSCLC. Patients should be on PD (L)1 inhibitor alone (i.e., with PD-L1 expression 50%) in the metastatic setting. The investigators will allow single agent pembrolizumab only as the checkpoint inhibitor.
• Patients requiring palliative radiation or definitive radiation to an oligometastatic disease prior to the initiation of single agent checkpoint inhibitors are allowed once radiation has been completed and patients have recovered from toxicities.

Exclusion Criteria:

• Self-reported weight loss of > 10% in the 6 weeks prior to study entry
• History of symptomatic hypoglycemia or uncontrolled diabetes
• Prior therapies with inhibitors of insulin growth factor I(IGF-1) such as Linsitinib or Picropodophyllin
• Concurrent use of somatostatin
• Concurrent use of immunosuppressive medications including sirolimus, tacrolimus, mycophenolate mofetil, azathioprine, prednisone, dexamethasone, or cyclosporine
• Significant food allergies which would make the subject unable to consume the food provided.
• History or current evidence of any uncontrolled medical or psychiatric condition, therapy that may confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the participating subject as deemed by the treating investigator.
• Pregnant or lactating females are not eligible.