I think so, I’ve read articles from dietitians that short term fasting is a great way to flush out your body, lower your blood pressure, cholesterol, and start using your body’s reserves. Of course this is only short term as your doing it within a few days. I’d say if you are relatively healthy, you may see a lot of benefits giving your body the time to recover after month of normal or abnormal eating.
Sounds a bit natural if you think about it. Maybe 1-3 is more natural but ig it really depends on you. If you feel you need the cleansing/weight loss then adding more days could be a good option if you’re wanting fast..er results.