Fat is burned pretty slowly. But people who are in good shape can access fat more more easily. That's just one reason to do walking. You can burn a higher percentage of fat by walking than by running. But you burn a higher number of fat calories through intense exercise. Either way, the people who work hardest seem to get the most benefit.
Sigh.
The weird and wonderful truth is that when you do an exercise like pull ups -- as I did today -- you're training not only your arms and back but your heart. Fit people's hearts work better. This is because an exercised heart is a stronger heart.The most important thing is that we can preserve or even improve our health with the right exercises. And it can be done, no matter how old you are.
P.S. My gym buddy Adrian took this vid of me today. I think my form is gradually improving. What do you think?