Well, I actually have this "extra" fuel I would be delighted to use: it's called "fat".

But it seems that it is not to be.

Only 10 or 20 miles

I remember Larry telling me that I need to fuel while riding.  I would ride from my cabin near Zigzag down to Alder Creek and back.  About 10 miles downhill (1500' to 900') and then back up.  It wasn't a big deal but I was pretty drained by the time I would get home.

Larry said "re-fuel" and while he mentioned things like energy gel, etc, I wasn't clear on what that really was.  It seemed too "advanced" or something, so I would eat my trail gorp mix: raisons, nuts, and M&Ms.  Seemed to work for the rides I was doing.

Then, I rode up to Kiwanis Camp, down to Alder Creek and, while riding up to Kiwanis Camp again, I bonked: the gorp wasn't doing it. Fortunately, the operative word is "up": US 26 is entirely a 2-3% grade heading down to my house. It is called "planning ahead". :-)

Hey!
I clearly have plenty of fuel in fat!  Come on, give!
But the greedy little devils just merrily sat there around my waist.

Then I learned about Energy Gel

Then I re-asked and re-listened and tried some "energy gel".
I started, haphazardly, using it.  It seemed to help but I was neither consistent nor knowledgeable.

I seemed to get "borderline" bonking.  Not a hard bonk, like that first time (and likely times in the long past), but a start to "run out of energy" as I was getting close to home.

Max Heart Rate and Greedy Fat Cells

It was a long road.
I got a Garmin Edge 305, for a lark, and recorded my heart rate (along with everything else).  It was interesting to look at the traces, think about the heart rate tables, and just have entertainment.
BAM! You fool! That "70% of Max Heart Rate"!
It hit me:
the reason I wasn't losing much "fat" was that 70% of max!
I was usually well above 70% as I slogged up the 600'/10 miles from Alder Creek or
700'/9 miles to Kiwanis Camp Road/ZigZag Falls!

Fool's Errand

According to the National Heart Association, expecting to fuel off of fat (burn fat) at my ride heart rate was a fools errand!
Those greedy fat cells stop delivering after 70% (or, at least, start slacking off).

What a bummer!
All that work and no weight loss.

Bottom line

Yeah, I sure better
"eat before you're hungry"!
I'm not going to make it from Seattle to Portland based on using my "stored fuel":
I'd just  !!FAIL!!