Ketosis makes me feel good and more energetic. Hard to say if it is all ketosis or some of it was absence of fruit. But in the lowcarb community, where some still eat processed food as long as it is still lowcarb, it's common knowledge that ketosis is typically associated with feeling good and full of energy. So my money is on ketosis as the prime generator. Fat is a very powerful fuel.
Personally, I think it is much easier to segway from paleo higher carb to paleo low carb, that it was to do go straight from SAD to paleo lowcarb. I think once you are eating healthier foods in general, the body tends to become much less sugar dependant and more capable of shifting to fat burning mode. Which I think makes a later shift to lowcarb much more natural.
However I am continuing to experiment with the macronutrient profiles. Lately, I've been cutting back on the carbs and will run that way a few weeks and then I am thinking I will try a bit more starch but no fructose and see how that goes. I am intrigued by someone else's post here recently that the starch only thing works for him for weightloss. I don't think I've read or heard much about that tactic so it makes me curious. Plus I like potatoes so it shouldn't be too unpleasant. (But if, on the other hand, it was an eat tons of Kale every day type plan, than I wouldn't be quite so eager LOL!)