The aim of this trial is a first evaluation of the effectiveness of intermittent fasting as a supplementary therapy in patients with CRPC or hormone-sensitive prostate cancer with high metastatic load (1≥ visceral and ≥4 osseous metastases) in respect to quality of life, reduction of side effects and possible reduction in tumor progression.

Prostate cancer is in Germany with approximately 25% of all cancers the most common cancer among man. Assumably there will be an increase in prostate cancer in the next few years because of demographic factors. The progressive metastatic prostate cancer often develops an androgen resistance. This so-called Castration-Resistant Prostate Cancer (CRPC) is not responsive to androgen deprivation therapy. Depending on symptoms and progression first-line chemotherapy - docetaxel and abiraterone are available.

Intermittent fasting as a form of caloric restriction has been studied most extensively experimentally in recent years. It showed consistent beneficial effects on relevant inflammatory and oncological pathways. In the field of preclinical oncology research groups have recently focused on intermittent fasting with chemotherapeutic treatment and promising experimental data have been published. In summary, the combination of fasting and chemotherapy was more effective in various cancer animal models than chemotherapy alone.

Inclusion Criteria:

• Diagnosis of CRPC or hormone-sensitive prostate cancer with high metastatic load
• Cancer is treated to guidelines conventionally with chemotherapy or with a combination of hormone therapy and chemotherapy.

Exclusion Criteria:

• Underweight (BMI <20 kg/m2) or actual weight decrease >2 kg or >5 kg in the last 1 or 3 months.
• Eating disorder
• Dementia
• Psychosis
• Terminal illness with a significant limitation of mobility and overall vitality
• Diabetes mellitus type 1
• Renal insufficiency stage > 2, GFR <60mlmin / 1.73 m2