Fasting for 7 days would be more beneficial than fasting for a day or two because after 4 or 5 days, the body systems "reset".
You will lose your taste for sweets, salt, and fat, and vegetables will begin to taste much better, since that is what we are "programmed" to eat.
Blood pressure and blood sugar will also normalize while on a 7 day fast, however, this should be done under the supervision of a good doctor in case there are any problems. As an example, you might become weak and fall
Dr. Julian Whitaker recommends only taking pure water during the fast.