IF should die and TRE should live.
For example - a regular 3-meal a day person (6 AM, noon, 6 PM) starts IF…
They eat dinner at 6 PM, go to sleep, and wake up and have breakfast at 6 AM and they say:
“Well! I fasted for 12 hours.”
But, they never went without food - they never fasted - they never did not eat when they otherwise would have.
If they eat dinner at 6 PM - wake up and skip their normal 6 AM breakfast and then eat lunch at noon they say:
“Well! I fasted for 18 hours.”
No they didn’t - they fasted (did not eat when they would have otherwise) from 6 AM to noon - a 6 hour fast.
IF has this problem of including time you wouldn’t eat anyway.
If you do not eat until noon (skipping your 6 AM breakfast) and say you fasted for 18 hours then going until dinner (a 24-hour fast) should only be 25% more difficult (6 more hours - 25% of a day) but it is not (for most). Instead, skipping breakfast (a 6 hour fast) and then also skipping lunch (another 6 hour fast) is 2 X 25% (or 50%) more difficult (going 12 hours instead of 6 without food).
TRE does not have this inherent problem of including time you are sleeping.
A 4-hour TRE window is half is big as and 8-hour TRE window and twice as big as a 2-hour TRE window - so the relative amounts of time your insulin will be raised are much more (my opinion) comparable.
Notice though that the same logic cannot be used for EF. I you say “I didn’t eat for a week” no one would say “Well you do not normally eat at night so, really that is a 3.5 day fast”.
So, sub-day - you are eating in a TRE window, greater than day - regular EF.