"If people ate more fat, and less (read no) wheat they will lose fat, as their bodies will process fat more efficiently. It becomes great fuel instead of a spare tyre."
Fat is a great fuel, that's why we store it - for the bad times. It's a great fuel IF you actually use the calories it contains. I can't imaging what you think happens to this "more efficiently" processed fat IF you don't actually use the calories it contains - do you think that this "efficient processing" makes it disappear into thin air ? Or do you really believe the bacteria in your gut can metabolise excess fat in the diet without consequence. At the very least you'll get VERY hot. Food is measured in calories for a very good reason. 100g of fat is 800,000 calories or 3MJ. If that's metabolised, by you or bacteria, unless you lose a lot of it as high energy waste (like methane) the metabolism will result in a good proportion of 3MJ appearing as heat. If a large proportion IS converted to methane that's in the order of ~~50L (which is flatulence with a vengeance)