I work in outpatient surgical center, lying to anesthesia can be really dangerous. I've had a person lie about not taking d***s and then react badly when given the anesthesia meds because they interacted (fortunately for that patient not nearly dying but I will forever have it ingrained in my head the anaesthetist leaning over their head screaming "what d***s did you take?!". Anotehr that I fortunately havent seen serious event but definitely has happened to our providers and I've seen more mild versions, people eating/drinking before the anesthesia and then denying. Lucky for my patients they just have puked after waking up so we know they had it but made it ok. The danger is you can puke during sedation and then get it in your lungs (called aspirating) and die from that. Could be really bad but fortunately I personally havent seen the worst yet, but I've heard plenty of stories of it.

Quit smoking (Edit: it’s been 10y now and most upvotes I ever got for anything, thank you very much).