Let me add my raw foodist perspective here...
Protein is - IMHO - an overrated issue. It's mostly a lot of hot air caused by grossly uninformed people who don't even know what protein is. Just read the thread "Stupid things omnivores say" and others.
Personally I don't worry much about protein - or any nutrient per say. As long as I feel fine while working out and generally all around, I know I get enough. I'd like to trust my senses here - I'd certainly feel if I get too little of such an important nutrient, no?
I've read just about any book about nutrition, veg and not veg, I cold get my hands on. I AM a very scientifically oriented person. I just finished the latest Harvard Medical School Guide to "Eat Right". And I have yet to find any evidence that a raw or fruitarian diet is dangerous, or deficient in anything. In fact, they seem to have the potential to be very healthy, and there's evidence that our ancestors were largely raw food fruitarians (duh!). But this usually goes under b/c these books (understandably) concentrate on the (un)health aspects of more "mainstream" diets.
Back whan I did worry about protein
, I have read many articles and did some calculations. I think if you eat a variety of fruits (and fruits only!) to get all your calories, you get something like 30-40 grams of protein a day from fruit alone. There are nutritionists claiming that this is all the body needs, if it is not overburdened with digesting nasty animal ingredients (=heavy lifting for the digestion system).
As Keegan pointed out, fruit does contain protein. And we are talking TONS of fruit here, not just 2-3 servings a day. If you
supplement with some leafy greens, plus nuts, I'd say you get "enough". If you eat 75% of your calories from fruit, 20% from leafy greens and the rest from nuts, you'll get actually *more* protein than you need.
There are fruitarians who succeed and there are many who don't. Those who don't, fail miserably. In my humble view, most of those who fail, do so because they simply don't eat enough calories and not because of protein or anything else.
If you eat like 1-2 bananas + an apple for lunch, of course you're going to be hungry real soon. Make it 5-6 bananas, 3-4 apples plus an avocado (something I would eat for lunch when fancying an all fruit setup), and you have consumed something like 1000 calories, and 12 grams of protein - fruit only.
As a "snack", I'd eat 1-1.5 heads of lettuce (12 grams of protein - lettuce has half of its calories from protein, and 25% from fat). Throw in some walnuts for good measure and you are at 30 grams protein, and ate half of your daily calories. See where I'm getting at?
Should you choose to consume grains and or legumes (e.g. in soaked/sprouted form), the protein percentage goes even higher, but I believe fruitarians avoid both of these food groups.
When on a fruitarian diet, you are on kind of an autopilot. You must eat until you're full, not until you
think you have eaten enough.
Bottom line is, that if you get enough calories (and you are not eating a monodiet of one single type of fruit), you will get enough protein. This seems very intuitive to me. Again, the main problem lies in getting enough calories. A lot of fruit has to be consumed.