Well fasting at times was normal. Everything enough though is questionable. We know that humans have been eating some high carb foods for ages. We also have every reason to believe that humans used to be more active than our "couch potato" current life. There were no office jobs, if you wanted to eat somebody had to chase down the food (sometimes a literal chase, sometimes just find it). Low sugar - there was plenty of fruit available at times. Of course this fruit did have a lot of complex carbs as well.