Fascinating as ever.

This is beginning to look a lot like an adaptation system to environmental food availability. Perhaps in our pursuit to avoid experiencing any negative feelings ever, we have optimised unavailability out of our diets - but our biology is built to run on EITHER fuel A or B, not both.

Perhaps crudely speaking we are awkwardly flip-flopping, burning inefficiently all the time as the machine never quite settles into one or the other.