Depends.

Most of the time I carry about a day worth of energy at any given moment as backup in fairly built up areas. Usually a couple of Snickers bars, salami, bananas etc

Have had to carry about a week worth a food a few times; not because food wasn't around but it becomes a pain in the butt to acquire . Small African villages tend to have nothing for sale but biscuits, baked beans and cola most of the time. Learned that the hard way; I would rather buy some nice food and carry it for a few days than eat nothing but baked beans again for 4 days straight.

I always enjoy reading about the tourist that go around in the desert sections in Australia; sometimes 30 days with no food supplies!