I'm a small farmer, on a permaculture farm (that's your source...me the farmer).
First, this question ENTIRELY depends on what plant zone you are in. I grew up in the Pacific Northwest, of Washington. It was plant zone 8. I could grow dang near anything. Even in the winter, I still had pasture for my livestock.
I now live in Idaho. I'm in plant zone 4B, borderline 3. There are bairly 90 days in which to plant, grow and harvest your crop, before a hard freeze, or snow will hit. Here the ground freezes several feet down to resemble concrete...nothing grows here at all in the winter, not even pasture.
You also cannot live off just fruit and vegtables alone. You need grains and legumes to provide complete protiens for your body.
An incomplete protien will feed your body. It takes a complete protien to allow your body to heal itself, and to allow children to grow. Example would be rice and beans. Eaten together, they are a complete protien. Individually, they are an incomplete protien. The other source of complete protiens of course are meat, dairy and eggs.
If the person has to grow their own grains, and legumes, along with their garden, and fruit orchard, they would be able to do so with an intensively farmed 5 acres (in the correct climate). Your grains of course are going to take up the lions share of your crop. You will need abut 3 acres of grains.
You need about 1/2 acre of fruit AND nut trees. Nuts are very important for adding viatimins and minerals to your diet
You will need about 1/2 an acre of "perminant garden." Those are the food items you do not plant every year. Items like raspberries, ruhbarb, apsperagus, your herbs, strawberries, blueberries, mushrooms, ect.
You will need about one acre of actual garden. About 1/3 of that is going to be taken up with your corn patch. Another 1/3 will be your potatoes (grow several types). The final 1/3 of an acre will be your intensively managed garden. There will also be overlap, as you will have some of your squash and pumpkins growing in your corn patch.
Some people will think I'm in error, and going too large, however I'm not. If you are growing your own foods, and eating only fruits, grains, vegtables, and nuts, you need a LOT of food. The amount of energy you will expend to plant, grow, harvest and preserve all of your food will be staggering. One person doing it alone, even with meachnical help, like a tractor, is still going to be expending about 5000 callories themselves during planting, harvest, and preservation times.
I know, because that is what my husband and I do on our farm. We grow/harvest/preserve most of our foods ourself.
Homesteading/Farming over 20 years