For 3, there's evidence that very low carb diets will improve insulin response. Over time it seems plausible that your body will respond differently to food if

For 3, there's evidence that very low carb diets will improve insulin response. Over time it seems plausible that your body will respond differently to food if your hormones stay out of balance, storing more of it as fat. How we store energy also depends on what exercise we get and its timing. Carb back-loading supposedly doesn't have the same insulin response because the energy is used to replace sugar (can't remember exact name, too lazy to look it up, sorry) in muscles instead of storing it as fat. The OP also links to a study that looked at several factors including microbiome. Genetically identical twins could have different response to the same foods. I'm pretty sure our microbiomes are very different than those of our ancestors, so we probably won't get the same results.