If you want to make subjective observations like "fasting makes me feel more alert" that is completely fine by me. I fully agree that it's possible to observe p

If you want to make subjective observations like "fasting makes me feel more alert" that is completely fine by me. I fully agree that it's possible to observe positive changes like this without knowing why the change is happening. However if you make a specific scientific claim about cell "cleansing" then you need to be able to back it up with evidence; without evidence, such claims are just nonsense. There is no "subjective observation" of what cells are doing.