One symptom of cancer, especially late-stage cancer, is cachexia: unintended weight loss. It is associated with a higher risk of death and lower quality of life

One symptom of cancer, especially late-stage cancer, is cachexia: unintended weight loss. It is associated with a higher risk of death and lower quality of life. [1] In addition, cancer treatments like surgery, chemotherapy and radiation affect the sense of taste, appetite and metabolism and make it difficult to get normal nutrition in the first place. So you can see why clinical oncologists and patients might be wary of restrictive diets or fasting. In fact many offical guidelines suggest adding sugar, frying foods, eating more dairy, etc to boost nutritional intake. Psychologically, even if a patient is overweight they may fear a drop in weight as a sign that the cancer is progressing. (An ex-colleague was very obese and lost 60kg before/after being diagnosed with kidney cancer). A patient may also want to enjoy their remaining time. Food has a huge intrinsic pleasure and is very important socially. I'm not saying this is an unworthy line of research but they will need good evidence or specific, easy interventions to convince people to change their diet. For example, drugs like metformin or rMETase may be easier than explicit restrictions. [1] https://en.wikipedia.org/wiki/Cachexia https://en.wikipedia.org/wiki/Cachexia