by MM, Survival Blog:

Introductory Disclaimer: What follows are my personal experiences and observations.  This information is for educational purposes only.  Although I am a physician, I am not your physician.  I am not providing you medical advice.  I am not a dietitian or nutritionist.  Before you consider taking any course of action similar to mine, consult with your physician.

—

Recently I completed a fast lasting 11 days, during which time I consumed zero calories.  I drank water and black coffee but took in no nourishment.  Notably, I never experienced hunger or a significant decline in function.  I lost approximately 25 pounds during the fast, but continued to work and do some wood splitting and manual labor during the period.  In truth, it was easy and I could have certainly extended the fast duration had I wished.