Had a bit of time to do some more analysis:
On quick, the cost of growing a population is 14

for the first, then 16, 17, 18, 20, 21, 22...
This means that, with a granary, some populations aren't even more expensive to grow than the previous! So growing to use all of your tiles with at least 3

is optimal for food-banking speed.
On normal, the cost always increases by 2

(1 with a granary), so growing to use 4

tiles is good, and growing to use 3

tiles is neutral for overflow banking. We still want to grow into 3

tiles though, since our maximum population depends on both the banked food and the starting population point
On marathon, though, things start to get hairy. Even with a granary, the cost of growing a new population increases by 3

for every population you grow! This means that, even if your city could work 4

tiles all the way up until size 20, this would grind our overflow banking to a halt (3 more

to grow + 2

eaten by the citizen is less than 4 more

worked). Of course in reality our cities will look even worse! So this brings us to the terrible, horrible, no-good, very bad idea of
banking food at 1 population. Heck, we don't even have to work a tile (which is good since we will be whipping this hypothetical city literally every turn

).
The setup: a city with a granary and sid's sushi co. It doesn't even need any workable tiles!
Each turn, the city grows from size 1 to size 2. It gains food from the city center (2) and sushi co (variable, note this was 42 at the end of the previous space game). The single population point eats 2 food, and growing to size 2 eats 66 food. The granary then refunds us 33. This means that the total change in food banked is (2 + 42 - 2 - 33) = 9. Whip down to size 1 and repeat as long as you are willing... voila! Lots of food in the bank!
EDIT: This provides an interesting argument for the Khmer. +1 food from the baray doesn't seem like much, but when coupled with a supermarket these two lowly buildings could give a 20% increase in overflow banking per turn. This also means every food from sushi counts.
But how far will this food get us? In order to grow in starvation mode, we must have enough food in the bank to grow in a single turn. No problem, right? We've been doing that every turn so far.
Our first population grown adds to our bank, same as before (bank gains 9)
Our second population grown requires 5 more food (bank gains 4)
And our third 5 more than that (bank loses 1)
Anyways, we can calculate out how far we can go with this before expending the bank, and it looks really bad. In fact, to grow n population consecutively we need on the magnitude of n^2 stored food in the bank! And the result is not even good until we can reach significantly higher than the old population cap (including worked tiles), which might be something like 40 or more! So to double our population, we might need about 80^2 = 6400 food banked, which at our rate of 9 a turn would take a whopping 700 turns to achieve

.
Conclusions / tl;dr
- Banking sizeable amounts of food is orders of magnitude harder on marathon than it is on quick, normal, or epic
- Because the strategy requires whipping down to size 1 (on marathon, at least), we can't work tiles since there is too much unhappiness
- Due to how long this whole process takes, it likely won't improve score on marathon. Still need to analyze more, but I believe the strategy could be instrumental for a score game played on quick or normal speed.
- One side effect of the strategy (insane gold generation via Q-whipping) could be part of a ludicrous new late-game economy, which might remove the need for STRIKE entirely. The downside would be the loss of caste system, but with cristo redentor we could stay in caste half the time.