Is it possible to lose all body fat? Should you eliminate all fat from your diet?

I just checked serving sizes for different kinds of nuts, and it turns out that I eat 500 to 1,500 calories worth of nuts every day. I eat a couple of different types (almonds, peanuts, cashews) and nut butters. I've never had a problem with this; I'm on the thinner size of average and feel relatively healthy. I know nuts are healthy for you, but can they be too much of a good thing?

Is wheatgrass as good as it's claimed to be? I have headaches when I drink it. Why is that??? Thank you very much.

I have noticed that whenever I eat certain sugary foods — especially chocolates and hard candies — I break out into a cold sweat and feel extremely uncomfortable for about half an hour. I have no problem, however, with pure cane sugar (when I drink coffee or tea, for example). Is this a normal adrenaline reaction to sugar, or a certain type of sugar?

How many calories does it take to lose one pound?

I am trying to convince my good friend not to save the grease she cooks with for re-use. Instead of draining grease out of a pan after frying it, she saves and stores it to use again. It seems to me that grease that is cooked once is bad enough, twice must be horrible. Am I unjustly picking on her, or am I right that there is an even greater health risk when you cook with pre-cooked oil/grease?