Well, to be fair, at the start of the war Defense Minister Yoav Gallant vowed that "there will be no electricity, no food, no fuel – everything is being blocked off. We are fighting human animals, and we will act accordingly." So they told us.
I think they know exactly what they're doing. Apparently (I just found out about this) in 2012 it came to light in a released document that Israel had calculated the bare minimum number of calories necessary to keep Gaza residents from malnutrition on order to let just enough food through the blockade. According to a report in Haaretz:
"The "red lines" document calculates the minimum number of calories needed by every age and gender group in Gaza, then uses this to determine the quantity of staple foods that must be allowed into the Strip every day, as well as the number of trucks needed to carry this quantity. On average, the minimum worked out to 2,279 calories per person per day, which could be supplied by 1,836 grams of food, or 2,575.5 tons of food for the entire population of Gaza.
Bringing this quantity into the Strip would require 170.4 truckloads per day, five days a week.
From this quantity, the document's authors then deducted 68.6 truckloads to account for the food produced locally in Gaza mainly vegetables, fruit, milk and meat. The documents note that the Health Ministry's data about various products includes the weight of the package (about 1 to 5 percent of the total weight) and that "The total amount of food takes into consideration 'sampling' by toddlers under the age of 2 (adds 34 tons per day to the general population)."
From this total, 13 truckloads were deducted to adjust for the "culture and experience" of food consumption in Gaza, though the document does not explain how this deduction was calculated."
So we can assume they know very well what amount withheld leads to starvation.