I’ve done this before. I was on a beach in Mexico back in the day for 3 days. Slept on the beach in a hammock. The nearest bathroom was about 30 minutes because it was a secluded beach. There was an outhouse you could shit in and I kid you not it looked like the poop scene from slumdog millionaire. I decided I would not shit till I left.

Honestly I ate normal food and it was fine so I think crippling anxiety is enough to make this possible.