There are two things that you can actually live on by themselves which are Coconuts and Potatoes

A friend of mine was recommending that I go on a Coconut fast. I have never done that before. So, as I thought about a diet like this to reduce one's weight I thought of an idea like having a coconut in the morning and a baked potato at night since that alone could sustain a person. Because just doing coconuts for a long time it's true you can survive on coconuts if you live near where there are coconut palms and can eat coconuts at every stage but only if you live near where coconuts are grown to eat them at every stage of development. However baked Potatoes you could eat too to prevent the runs you might get from only eating coconuts a long time. So, I was thinking that you might eat a coconut in the morning and then a baked potato at night as a way of reducing your weight but still getting enough nutrition to sustain your body for a long time (like 40 to 60 days). However, I haven't worked out all the details but it is an interesting idea that I've come up with for dieting without losing all the nutrition out of your diet in losing weight. However, until I try something like this it is only theoretical at this point.

Also, you would have to find a place that sells whole coconuts and then be able to harvest them without injuring yourself which is no small feat either. Whereas Baked potatoes can be baked in the oven or even microwaved for 5 to 8 minutes depending upon the size of the potato (or potatoes) and how many you are cooking.

Anyway, it's an interesting idea that I haven't tried yet. 

NOTE: You would only want organic coconuts if possible and you definitely need organic potatoes because like Carrots and Apples, potatoes absorb into their flesh or meat directly any insecticides used on fields and you don't want the spray in your body while you are dieting or at any time really.