Not so much.
I can't find direct numbers, but a little bit of math can still get us there...
In 1943, Japan proper had about 73 million citizens, and imported the equivalent of 2 million tons of rice.
That sounds like a lot, right?
But 73 million active people would eat the equivalent of nearly 50 million tons per year, meaning imports supplied only 4% of their needs.
The rest must come from Japan's home grown production.
The loss of two million tons of imported rice would equate to roughly 100 calories per person per day.
So the Japanese would not starve, period.
They had to be defeated, and the only choice other than A-bomb was invasion.
Given their fanatical resistance, invasion would cost hundreds of thousands of Americans plus millions of Japanese.
So our A-bombs over Hiroshima and Nagasaki were simply the most merciful way possible to end the war, quickly.
The Japanese soldier certainly wouldn't, for the civilian population wouldn't want to be them. Most certainly, the US POWs would have starved.
The Japanese relied upon imports for more than rice. Much of the grain and meat came from the mainland. But more than that, it was not the actual food as much as the internal food distribution system. By July 1945, the allied blockade had become internal to home waters. The coastal shipping that Japan relied upon for domestic commerce had been savaged by air attack, mining and submarine operations. The internal rail links were fragile, and were the next items on Curtis LeMay’s interdiction schedule.
Richard Frank documented all of this in “Downfall.” The Japanese were already on starvation rations during the summer of 1945. The destruction of the internal rail links would have reduced the food consumption even more. Frank estimated that as many as 20,000,000 Japanese would not have survived the winter even without an actual invasion. And those deaths would have been predominately the old, very young, and sick. Think of Leningrad on a national scale.
In fact, the very first thing the American occupation forces realized was that the Japanese were starving, and immediately began a program of food relief. Even though such an action was not politically popular in the United States.