This is a Phase 2, randomized two-armed, multi-site study of 138 patients with metastatic castrate sensitive prostate adenocarcinoma. Patients will be randomized 1:1 to receive the fasting mimicking diet, or usual diet. All patients will receive standard of care treatment for their prostate cancer. The fasting mimicking diet will be consumed for 5 days per month for a total of 6 months and will be monitored by trained research dietitians.

This study aims to examine the effects of a fasting mimicking diet (5 days per month eating L-Nutra products only for 6 months) vs. usual diet on response to cancer treatment of metastatic castrate sensitive prostate adenocarcinoma.

Inclusion Criteria:

• Metastatic castrate sensitive prostate adenocarcinoma (Adenocarcinoma prostate histologically confirmed by biopsy AND Metastatic disease confirmed biopsy, or MRI scan)
• Men receiving or planning to start first-line intensified ADT (within 30 days of registration) with abiraterone, apalutamide, enzalutamide, or darolutamide with or without current or prior chemotherapy
• Reads, writes, and understands English or Spanish and has telephone access for remote contact with the study dietitian.
• Written informed consent obtained from subject and ability for subject to comply with the requirements of the study.

Exclusion Criteria:

• Allergies to any ingredients listed on the Xentigen Ingredient List
• Men with diabetes who are not on stable doses of antihyperglycemic medication for at least 6 months and without physician consent that they may safely hold antihyperglycemic medication during the 5 days of FMD
• Regularly practicing a fasting diet that in the opinion of the study physician would impact study participation
• Significant co-morbidities (i.e., cardiac, pulmonary, liver disease, ongoing alcohol/drug abuse) that in the opinion of the study physician would preclude enrollment in this study.
• Body Mass Index (BMI) <20kg/m2
• Men actively trying to lose weight OR on weight loss medications (including but not limited to Contrave, Saxenda, Xenical) or planning to receive weight loss surgery in the next six months
• Self-reported weight loss ≥ 10% in the last 6 months