Asklemmy

If you're lost in the woods with nothing, you don't start to look for food.
You can live without food for 3 weeks, and if you happen to eat something wrong, you can get violently ill or poisoned.

Here's what you do:
First you try to call for help, or wait for help, if you know someone is looking for you.
If not, you start to walk downhill (even if it's just a barely noticeable slope).
At some point you'll find water (a creek, river, whatever), or at least a dry river bed.
Then you follow that downstream until you're literally out of the woods.

That way you aren't in danger of walking in circles, and rivers generally lead you to settlements.
There's hardly any spot on earth left where you won't reach the nearest settlement within a week (i.e. before you die from hunger) that way.

First, go up to the first tree you find and start punching it until wood cubes come out. Then craft a stick with the wood cubes. Then use the stick to beat the first sheep you see to death until cubes of meat pop out. j/k

Do what superkret & nemo said in their comments. Don't worry about food, focus on finding water, and getting rescued.

What part of the world and what time of year?

In general, you want to prioritize rescue over acquiring food and water. A set of three markers in a triangle that can be seen from above is a universal sign that someone needs help. Flashing mirror at any passing aircraft is also good.

For food, don't worry about it until after you secure water and shelter. It takes well over a week to starve. Water, boiling is best; you can do this even without a pot by heating rocks in a fire and dropping them into a basin you've filled with fresh water. Failing that, fast-moving streams are somewhat less likely to have as many parasites and dangerous microbes. But boiling is best!

For shelter, building a lean-to with fallen wood against a big rock will do for your first night; break off leafy branches and layer them over top to shed water. Longer-term, big sheaves of long grass bundled and stacked will insulate and shed water better.

To give you an actual answer, and you will probably not like this answer - you eat everything. Eventually. And it won’t end well.

You have only your hands, so you won’t catch any meat. You could try to make tools to make traps or catch fish, but that’s really hard.

For the first week, you probably won’t eat much at all. The hunger will fade after the first 24 hours. But after a few days it will come back, and it will come back strong. You’ll do what babies do - taste everything.

You won’t have tribal knowledge passed down, so you’ll rely on the backups - smell and taste.

Put a little bit of whatever it is in your mouth. If it’s bitter, spit it out. If it makes your mouth tingly after a few minutes, spit it out. Otherwise, swallow it. Wait an hour. If you’re still alive, and feel okay, that thing is probably okay.

You’re going to eat lichen, moss, tree buds, flowers, lots of roots, and strange berries. You’re going to turn over rocks and eat grubs and worms. You’re smart enough to shy away from mushrooms - at first.

Eventually you will be so incredibly hungry, and you will see mushrooms with mouse chew marks, and you’ll think to yourself: “if the mice can eat it, so can I!”. You’ll probably be right, and regardless, the gamble between a new food source and death will seem like a win-win.

Eventually you will get it wrong, and it will hurt the entire time that you’re dying. Life sucks. Your best bet is a few lucky guesses on something relatively abundant so that you can stop guessing.

Longer term, eventually you will figure out those tools you were attempting between foraging runs. Even longer term, you will re-invent farming, and even might not die of a vitamin deficiency. Good luck!

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Practical answer: don’t do that. Ignore food. Get rescued. Go downhill. Most of civilization is on the coastlines and/or riverbanks.

And drink the water! If you only have gross water and no way to filter or boil it - drink it. The difference between death by dehydration and death by bacteria is about one to two weeks, which is more than enough to be rescued. The hospital might be able to fix you sick. They can’t fix dead.

To build on the good answers from superkret and nemo...

The survival Rule of 3's says that, depending on your situation, you can generally survive:

• three weeks without food.
• three days without drinkable water.
• three hours in a harsh environment (extreme heat or cold).
• three minutes without breathable air, or in icy water.

Finding a way to stay warm and dry at night should probably be your primary concern. Hypothermia kills fast.

water

The others have given great responses, but I thought I should mention that having a lifestraw could save your life. It filters the water as you're using it, and it has saved lives in similar situations!