Yes, when it comes to denying nutrition. Absolutely. It does not happen that often. If one really wants that, then write the living will, and make sure it can be found. Which reminds me, that I need to write one, because I would want an early exit.
Last summer, shortly after one of my sisters was diagnosed with malignant melanoma and her husband was diagnosed with a calcified blood clot in his brain stem, I made sure the rest of us had living wills.
My sister had all of her melanoma surgically removed and it hasn't come back. My brother-in-law, also a heart transplant patient, is still recovering. Both have had living wills for years.