It depends. Do you measure your runs? I can run a 13mi run, and maybe some extra, without gels. Even without water. But in my experience I can't do it for a 20

It depends. Do you measure your runs? I can run a 13mi run, and maybe some extra, without gels. Even without water. But in my experience I can't do it for a 20+ mile run. And my fasted runs are generally slower than nonfasted runs regardless of how I actually feel while running it. For example, when I train every day, my morning runs before a full day of eating are abysmal. My evening runs are nice and fast. Worse still, when training every day, I've noticed that what and how much I eat the evening before, has a huge impact on my morning run as well. (I tend to do my long runs early in the morning because fitting a 4h run in the evening is tough) Maybe my problem is the every day training part. It makes nutrition crucial so I can get enough recovery out of my body.