This is more a thought than any kind of researched analysis.
I suspect the best form of diet (for weight loss) is one in which you cycle fat/carbs/protein as the major energy providing part of your food on a relatively short time scale (probably switching every 3-4 days; although it might be more practical to use a weekly cycle). The reason for thinking this is that the cells in your stomach take several days to adapt to a new diet.
In experiments in mice it takes 3 days in mice for epithelial cells to be switched for ones adapted to digesting food from a new diet, before this time they fail to extract the full calorific value of the food from the diet, and a large potion it passes undigested out the other end of the gut. It might causes you unpleasant bowel problems as a result, I suppose, but I expect with a little practice it could be tuned reasonably well.
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