Can we survive on liquid food only our whole lives?

I don't get it. Food turns to liquid anyway in our body. So... why can't we survive on water and liquid food only? Oh, I've read about a grandma who lived for 9 months relying on those only but then again that she had dementia  so she probably didn't notice any bad experience through it all before she died. But this guy is completely sound in mind (okay, maybe a little bit traumatize) and he said he feels hunger all the time from relying only on water and liquid food.

Which is strange to me because like I said, food turns to liquid anyway in our body. So why do we feel hunger without solid food? Or is it maybe because he didn't take enough calories, vitamins and minerals that make him feel that way? Or could it be completely psychological? I mean, one of the reason why people might get fat is because they eat too fast. So the trick is to chew the food slowly as to give time for your brain to recognize that you're no longer hungry.

So can we survive on water and liquid food only our whole lives? It seems like a very feasible idea.

But do we want to? Eh, that's an entirely different question.

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Answers: I am no biologist to say for sure but based on the answers I found, I have to say that it might be very very possible to survive on these.

According to this guy, he said he's okay and not hungry, just craving to chew solid food. And like I suspects, needing solid food might all be just psycological.

Excerpts:
I am currently recovering from jaw surgery (probably of the same type that i_am_a_fiesta mentions) and have been on a liquid diet for three weeks and will be for the next five to seven. I have no experience with dieting or weight problems, but I can address the psychological side effects that come with drinking all of your meals: I am going completely crazy without chewing anything. My body is so desperate to bite into something solid that last night I had a dream I was eating golf balls. Golf balls.

I am getting enough calories that I am not "hungry," per se, but without any texture, meals are never really "satisfying" for me. Obviously if you embark on this liquid diet (and I am not saying you shouldn't), the psychological boost you get from any weight loss you see might outweigh the urges you have to chew something. But don't underestimate that particular urge and how it might gnaw (ha!) at you over time.

And there's even a guy who tried a 2-months water and liquid fast on that forum and what he said is true (at least on my experience). I ate mostly liquid food, salad and moist food (raw fish anyone?) during my about 1 month Raw Food Diet Challenge. And like him, I lost weight and any food craving. However unlike him, I felt hungry all the time because I didn't eat as much as I should (I'm a bad chef).

Excerpts:
Here's the weird thing about fasting, the thing that really makes it work well for me, personally: fasting is much harder at the outset than a normal diet because of the radical change. But if you can last for ~2 months without food at all -- no cheating -- cravings for food ramp down very dramatically.

You'd think that after fasting for several months, you'd want to binge at the end of the diet. But that's not the case: if you can get through those first two months, and lose a whole lot of weight down to your goal, transitioning to food is actually easier than with other diets -- schroedinger be damned. Since you have a blank slate, since cravings are under control, and since you go from eating no food to eating a full diet step by step (ie, veggies first week, lean meats in the next weeks, fruits the weeks after that, etc.), it really helps slowly build a wealth of knowledge of understanding of portioning and cooking the individual parts of meals to maintain.

But ultimately, the loss of cravings is the weird part of the liquid fast. After a difficult couple of months, you don't feel hungry or uncomfortable. Even though you keep losing weight, with sufficient protein intake, one's body seems to adapt to the shakes and body fat as an energy source... and everything keeps going. You go from feeling like you're starving to feeling normal. Then, you go from feeling normal to feeling... really very good. You'd think without eating your energy level would keep dropping, but by the end of the liquid diet, you may find that you have more energy than you thought imaginable.

I did it wrong for one month, felt hungry all the time and yet I'm still alive, got better energy level and doesn't feel sick at all by the end of the challenge.

He did it for two months, got great energy level and he definitely doesn't feel hungry at all.

There's a even a liquid fast program that claims:
Some people think that you have to eat three meals a day to stay healthy. Some people also live to eat instead of eating to live. We personally know people who have gone for more than one year without eating any solid foods but taking juices and broth only. The Gerson cancer program, which have cured many terminally ill cancer patients, recommends 18 months of fasting on juices and broth.

All in all even without solid evidence, all these confessions and real liquid fast programs does point to a very agreeable hypothesis about a human CAN survive by water and liquid food only whole life (or at least for a very long time), isn't it? I think I'll try it someday.