None of these:
>>awake and breakfast at ~6AM, dinner at 4pm, lights out at 9PM (and no meal until breakfast the next day.)
..fit your criteria.
Lights out at 9PM and waking up at 6AM gives up to 9 hours of sleep. That's plenty.
Similarly, going from 4:30-5PM until 6AM without food is not a huge deal, especially since you spend most of that time sleeping (in fact, not eating immediately before sleep can be very beneficial for sleep quality).
Before you adjust, having a meal at the wrong time and sleep at the wrong time can be somewhat equivalent to skipping both of them. If you ask me to fall asleep at 9PM without any previous setup, it will not happen, and I will not be rested at 6AM.
In a Vipassana retreat it's actually no food after noon, so that would be 12PM to 7AM iirc (haven't done a 10-day retreat in many years).
And it isn't a huge deal as you'll likely have other things on your "plate", such as a heaping portion of pain in the X (where X is your knees, back, buttocks, etc.) to keep you full :)
TFA references Megan Vogt, not sure if anyone has posted this yet:
https://www.pennlive.com/news/2017/06/york_county_suicide_me...
Boot camp has some things in common, because it is quite the indoctrination, but they feed you well, and focus more on breaking down the ego and forming a group identity and esprit de corps. Cults focus on breaking people mentally and creating dependence. Interrogation tends to focus on disorientation and a need to bond with the interrogator. Meditation retreats focus on breaking existing habits and perspectives and instilling new ones.
Similar tracks, different intentions and outcomes. Another difference is that in the military you’re screened for prexisting psychological issues, and they have a vested interest in that screening process. You also have trained observers at all stages who know to look for signs of deterioration. In a retreat you have no screening, no such resources, and no training in recognizing early signs of psychosis.