Since there seems to be a persistant effect of people losing weight when they start a diet and then regaining it presumably because their digestive system learns that the food has calories and makes them crave it more, I wonder what would happen if someone changed diets everytime right after the initial weight loss from their previous diet. I have mostly only heard about this effect, so I am not sure what the timescale of each diet should be. Also, I wonder how much long term memory the digestive system has, presumably a suitably large rotation would work. (And have we historically, before advances in agriculture, been forced to do this somewhat by food going in and out of season?)