Cancer patients who are receiving chemotherapy should reduce their intake of calories and protein by fasting because this practice can help protect patients against the toxicity of chemotherapy, according to a report published on nature.com.

The report indicates that fasting for 5 days followed by eating a normal diet can protect patients against chemotherapy without losing weight.  

In contrast, following a long-term calorie-restricted diet with 20 to 40 % calories reduced can lead to weight loss even though it can produce a similar yet moderate beneficial outcome.  

Keep in mind that American Cancer Society recommendds that cancer patients receiving chemotherapy should increase intake of calories and protein, according to the report.