Is doing a week-long fast healthy if you start eating normally the day after it is over?

The only fasting that I know is done that is okay is if you have surgery done or a blood test. No fasting is safe or healthy. You must eat healthy all the time. Trust me I know. I used to be anorexic. It is amazing what kind of damage I have put my body through. Please eat healthy.

Caveat:

Anorexia Nervosa is an eating disorder; that is, a compulsive behavior brought on by an underlying psychological disorder. The sufferer typically has little positive control over the condition, leading to the well-known emaciation most people associate with the disorder. Fasting is not analogous to this, or any, disorder.

To answer the original question, no. You shouldn't consume pre-fast-level food immediately after a week-long fast. The accepted wisdom is that the re-feeding process should be equal in time to the amount of time spent fasting, beginning with fruit juices and slowly introducing heavier foods until, in your case, day seven. Beginning day eight, pre-fasting-level food intake may resume.

This also depends on the austerity of your fast. A strict water-only fast absolutely requires a delicate re-feeding program to avoid illness. A more forgiving juice fast or calorie-restricted quasi-fast still requires care in reintroducing heavy foods, but not quite to the level of the water-only process.

Everyone prefaces diet regimen concepts by telling you to speak to your doctor first, but fasting is definitely something you need to see your doctor about first. If you're a teenager or if you have some underlying medical condition, fasting can do serious and possibly irreversible damage to you. Make sure your doctor confirms that you're healthy before you begin a fast.

That said, if you take care, plan it out and do it right, a week-long fast can be of great benefit.