In addition, reasonably strong evidence points towards shifts in microbial communities that can induce cravings. Thus, your microbiome can be "addicted" to certain foods and pass that on to you. Intervention at the microbial level may be helpful for some people, including microbiome transplants. However, my impression is that we're still largely stumbling in the dark in this area.
I recall having this theory quite a while ago. Let's say your diet includes eating powdered sugar donuts in the morning. The gut microbes that feed on it become plentiful. Then when you switch out diets, that particular microbe starts to die out. Then as they die, they release a hormone that causes the gut to signal the brain to crave that particular food type, and this is an evolved behavior for that microbe. And after a while of switching up the diet, those microbes finally get purged, and you don't have as bad of cravings anymore.
At least this is the sequence of events that really makes sense (to me), but I haven't read this in any research yet.
I wonder if it is also the case that some feedback mechanism in our digestive tract exists in order to try and preserve those bacterial populations. Perhaps it works in tandem with the signalling you mentioned. The idea seems plausible, but this is just speculation on my part.
