Thank you, Doug! I’m thinking more of western folks who move from SAD to a fruit based (or starch-based) diet and don’t get diabetes (and they’re often eating many times/day). I think that there’s something about extremely low-fat that changes the insulin pathways.
Re metabolic flexibility: I guess it just makes sense to me that except for those of us with Inuit genes, our history probably involved periods of higher carb eating (without devastating metabolic consequences), and many folks who are quite serious about ketosis and have played with it for a long time (e.g. Peter Attia, Mark Sisson) don’t actually recommend staying in it all the time, or at least don’t seem to recommend that for everyone. Although I’m very well-versed in ancestral eating, ketosis is a relatively new area for me so I’m still pretty early in my research and in my own experimentation.