Another thing a some folks on Weight Watchers may notice is that they get constipated if they aren’t getting enough fat in the diet. Adequate fiber and fluid aren’t enough by themselves. I’ve had it happen to me - adding a healthy fat, like peanut butter, helps things get running smoothly again. 
Adipose tissue cells (such as visceral fat, etc.) are essentially storehouses – fat can both enter these cells and be released from them as needed by the body for whatever function (release of energy, tissue repair, etc.).
I am thinking this was a whoosh guys. An implication the body cannot produce fat on it’s own would mean you cannot gain body fat without eating fat – which is clearly false.
If I remember correctly, total fat deficiency will kill you first, total protein deficiency kills you second and total carbohydrate deficiency will make you sick but might not kill you for a long time. No cite though.
I have an anecdotal cite that without essential fatty acids your hair will begin to fall out (sometimes to extremes) and skin and nails become dry and brittle. Gastric bypass patients have to take supplements to ensure that this does not happen during rapid weight loss/lack of absorption of these lipids.
You could get these from a daily capsule also.
You get odd cravings on an extremely low fat diet. Dudes who were able to kill and eat lots of rabbit but didn’t eat the organ meat got some strange dietary problems. (Rabbit meat has next to no fat.)
Heck yeah.
I need to find a copy, maybe it’s on the web by now somewhere but the older USDA Agricultural handbook #8 breaks down the nutrional value of just about all the foodstuffs. Very handy for anyone looking to keep track of exactly what they are eating. Fatty foods provide long lasting “keep you going” calories without getting hungry for a while.
I have a fairly severed addiction to Little Debbie Nutty Bars. I ate a whole box once and then saw the calories, couldn’t believe it. I had just consumed something like 1600 calories. Frankly I never feel sated eating “healthy”, too much crunching and munching, when I could eat a nice huge roast or steak in all its arteriosclerotic splendor, dripping with krauterbutter and garlic.
I try to avoid “fads” in diets, and I’ve lived long enough to see them come and go - and then come around again, albeit with a new name. I have no idea why this occurs, but something to do with selling books no doubt. For example, the “low carb” diet so popular recently was called “the drinking man’s diet” in the 60’s. Medical professionals didn’t like it much then either.
Not meaning to hijack, but I think you might quite like this source too, Common Tater. Detailed breakdown of foods, and with pretty charts and colours too, to take one’s mind of the health or ill-health. 
Fat in one’s diet does not equal fat gain in one’s body. Fat has more calories than the other two macronutrients, but if I were trying to watch my weight I’d be more worried about sugar intake than fat intake.
I did try a low fat diet several years ago. I consumed only about 10 grams of fat over a 15 hour period, and by the end of the day I was lethargic, listless and somewhat depressed. And after eating a couple tablespoons of peanut butter, I felt great.
Dunno … only charizard can say.
So far the cites on the conversion of carbohydrates to fats all say that certain organisms do this but do not say which. Do these certain organisms include humans? Otherwise I think that the cites are not particularly apropos since the OP seems to be about human nutrition.
Yes – humans are included. The first several results of a Google search on “simple carbohydrates”, “turn to fat” confirms this in short order.
You people can’t be serious! If humans couldn’t make their own fat you wouldn’t be able to gain a pound of body fat without eating a pound of fat — that’s a ridiculous proposition. You’ve seen people gain 15-20lbs of body fat in a scope of a couple of months, haven’t you? Are they all eating two sticks of butter a day or what?
Am I missing something? I just can’t wrap my mind around how you can be skeptical about something like this at all? To me it sounds like walking out of the bathroom thinking “Huh, that’s funny, I certainly didn’t drink any urine. I wonder where THAT came from?”
From a site making claims about the role of fat in pre-historic diets
I make no claims about the accuracy or up-to-dateness of the info on that page, but it makes an interesting read on (one side of) the debate on prehistoric diets and health