Distance running - "train" your body to burn fat?

Factual Questions
1

So I’ve recently become hooked on distance running. In many of the books and articles I’ve been reading, the authors refer to the need for long distance runs to somehow “train” your body to use fat for energy. I’m not disputing that’s what happens, but I’m trying to figure out what body part is getting “trained.” A gland? How does it “learn” to burn fat? Or is this a pseudo-scientific explanation for “eat less + exercise more = lose weight?”

Len

2

In short, being in better aerobic condition means that your body can get a higher proportion of its fuel from stored fat than it would otherwise. Releasing stored fat requires enough oxygen that it’s the limiting factor in how fast the reaction can proceed.