All very true. Beginning riders usually have trouble accessing their fat stores and need to eat more carbs more frequently than fit riders. Those who have been fit for decades may have never experienced that because they got fit when they were young and essentially fit in the first place. Only those who came to cycling later experience what you have noticed.

That said, the advice to work on accessing your fat stores is still good advice. One has to gradually work into it though, very gradually denying that urge to eat at the first sign of hunger. A good time to work on that is first thing in the morning, before eating anything and thus beginning the day's blood sugar ups and downs. I used to get up, have a cup of coffee, and get on my rollers for 1/2 hour before breakfast. Then I started going out with a bottle of sports drink, but holding off drinking any of it until I started to feel a little weak. I'd get hungry after about 45 minutes, but after a while I could ride through that feeling, whereupon my fat burning would start. Eventually, I could ride for a couple hours and never feel hungry or touch that bottle. Always take it along, though.