Early game food
Food is really not a problem when starting out if you play sensibly.
To begin with, don't run around and jump around needlessly. Walk. Make stairs. The more you run and jump, the faster you burn through your food. Early game is about taking it slow. Trees don't move very fast, and they only move as needed. If you're playing it right, you won't even need to eat anything in the first couple of days. That's plenty of time to get a food source started. And remember that we aren't on the hardest difficulty. Even if it's taking a while to get food growing and you begin to starve, you'll only go down to half a heart. Just be careful until you can eat enough to heal up again.
Grass for seeds is plentiful, and you can plant and grow seeds without water. Also plant seeds in rows with at least one block space between rows. Planting identical crops in clumps cuts their growth rate in half. You can alternate rows of different crops if you need to plant in a clump for space saving. Villages have lots of crops to get you started. Begin near a village or other players who can help you out in the early game if you want a good starter boost.
For a small boost, you can use "/kit growth" once every 6 hours to get 6 bonemeal.
And breeding animals is even more efficient than eating bread. It only takes 2 wheat to breed cows to get at least one steak, which is more filling than bread that requires 3 wheat to craft.
Giant mushrooms are a good food source if you happen to be in a biome that has them or small ones you can bonemeal. Growing a couple of giant mushrooms will get you a lot more food than using the same amount of bonemeal on wheat.
Chickens are also a super easy food source. You don't even have to breed them. Just trap one in a hole and collect its egg to throw back in the hole every 10 minutes or so. On average you'll get a chick for every 8 eggs, and the more chickens you get the faster your eggs pile up. Once you have a few laying you can toss the eggs into a separate hole for "harvesting" free meat.
Hostile mobs can provide resources useful for food as well. You can kill a spider or two to get a fishing rod for fish if you happen to be near even a tiny patch of water. Skeletons can be killed for their bones to grow crops or mushrooms. If you're already starving, just eat rotten flesh from zombies. It'll stop the starvation damage. Very short term fix, yeah, but better than losing all your health when you have a pile of flesh doing nothing, anyway. You can even eat a bunch of it to regain your health if you have it in bulk. Killing zombies for flesh even has a chance to get you a potato or carrot to plant.
If you're starting somewhere you don't have any of these resources, that's your fault. This is a challenge, after all, so don't expect to be living on easy street irregardless of your choices. If you want to play on easy street, plant your tree there to begin with. You choose your own difficulty by selecting the spot for your tree.
I'm sure there are even more ways to get food that I haven't thought of to list today. That's where the fun is. The whole point of playing a challenge like this is to find creative ways to overcome difficulties. If everything is just handed to you then there are no difficulties, no creativity, and no challenge. That's what makes people get bored and leave. Your base instinct may tell you that you want a simple way to do things or a fast way to do things, but the reality is that having it too easy is unbearably dull and completely counter to your desire to play a challenge in the first place.
Experience the challenge and have fun. 🙂