Is it Possible for a Human to Survive Eating Only Protein and Fiber Supplements?
Jim Moore • May 18, 2020
Survive? Likely. Thrive? No so much...

Survive? Seems likely that it would be possible for a human being to survive on the nutrition regime you describe. According the article below, comatose patients, who by the nature of their condition are unable to take nutrition via the mouth, can survive and even repair their biological systems with a nutrition regime that is little more than protein, calorie and vitamin supplementation:
An important caveat to the survivability of a supplement exclusive diet is to assure that you are consuming the necessary amount of water. Hydration may have been implied in your question, however, if it was intentionally not included, proper hydration is important to any nutritional regime.
Before starting a regime like you have described, a consultation with your physician would be necessary. A conversation with a psychological counselor may also be valuable to discuss the reasons you would be interested in forgoing “food” in favor of a supplement exclusive diet.
A couple of additional articles that may be valuable to your understanding:
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