I love cake. But a bit put off sweets after yesterday, felt like my teeth were erroding by the end, with energy gels, gummies, citrus flavoured sports mix dissolved in my water, oreos, flapjack, pbj sandwich... I don't know how you did it on so little food!!!!!
I did say on your other thread to have some savoury even though for the distance you were doing, you can get away with sugary stuff.
Now for some science. You ask how some can ride so far and not need to eat very much. You’ve essentially got two energy stores, your fat reserves, and your glycogen stores. You’ve also got ATP for sprinting.
Glycogen is stored in the muscles and in the liver. Glycogen stored in your arm muscles can’t be used by your leg muscles. But glycogen in the liver can. Muscles use their local glycogen store first, followed by the liver. You have about 2000-3000 calories of glycogen stored if you are rested.
Fat is stored round the body as we all know. We have about 100,000 calories of fat reserves. Even the skinniest person will be close to this figure.
When cycling you’ll be burning between 400-600 calories an hour. So worst case glycogen will be used up in 3 hours, or may last around 7 hours. Fortunately we have those fat reserves and even at 600 calories an hour thats 166 hours it’ll last almost 7 days. For sprinting our bodies make ATP but that is for only short sharp bursts such as getting up a steep bit of hill quickly.
But we don’t exclusively use glycogen for fuel or fat for fuel we burn a mixture. The mix depends on our fitness and the intensity we are working at.
Fitness is a wooly term so what am I referring to? You can train and improve the amount of fat the body uses (for energy) at all intensities. You’ve head of the long low intensity rides, those slow rides that feel effortless and aren’t doing anything. They are not just about getting time in the saddle. It actually gets the body to adapt and produce more of the enzymes needed to utilise fat as an energy source, your capillary network in the muscle also gets denser for delivering oxygen and remove waste products from the muscle . Research says the rides need to be at least two hours and increase the duration as you get used to it. Then there is high intensity which forces the heart to adapt and get stronger, and for more muscle fibres to get recruited or added. Combine the two, in the right proportions , and your endurance fitness will come along in leaps and bounds. You’ll be burning more fat at higher intensities, meaning you don’t need to eat half as much, and you won’t be exhausting your glycogen on a long audax. Your heart is able to deliver more oxygen rich blood at lower bpm, and your muscles are more easily able to utilise the oxygen, your fibres are stronger , the muscles aren’t working as hard for a particular intensity, you have more fibres and can store more glycogen. Your legs are more fatigue resistant.
Back to sugary snacks. When sugar spikes in the blood, and we have more sugar than we immediately need, then insulin gets released. The insulin helps convert the excess sugar to be stored as glycogen in the liver and muscles. But another affect of that insulin is that it suppresses your body from burning fat for energy. In effect your body sees the excess sugar and thinks it means it can burn the glycogen instead. You are tapping into that energy source that will only last a few hours and not the one that can last a number of days. Once the sugar is dealt with and insulin levels drop, your body will start to utilise your fat reserves as a percentage again.
If you think about it. Our ancestors might do some high energy hunting for a few hours, burning glycogen. Then sit around for long periods burning fat. It’s only recently we’ve had easy access and frequent access to foods high in sugar.Our bodies haven’t really adapted since the days we were hunter gathers. So what happening kind of make sense from an evolutionary point of view.
Foods have a glycemic index which indicates how quickly the sugars are released into the blood. If it releases quickly into the blood you get that spike and insulin quickly rises to combat it. It’s why it’s suggested you eat low glycemic foods like porridge, slow release. You don’t get the big spike, nor massive release of insulin , so fat burning can continue as no big excess of sugar in blood stream.
Sugary snacks are great to dig you out a hole and say get you to the next shop 20 mins away. But they should not be regularly snacked on, on a long ride, as it’ll just cause your energy levels to alternately peak and then slump, and eventually bonk as the glycogen is burnt more and runs out.
Some of this based on experience, and some based on the science I’ve read.
I guess my legs are fairly strong, but over the years I've learned what my body needs/can manage on with regards to food & drink. I'd been back into cycling a few years before completing my first century ride so you're well ahead of me 
you might get a 200 mile ride in before me, Mine will be sometime next year hopefully.
I finished day one (360km) and I knew I was screwed and nearly packed then but figured I would just try and get as far as I could , I ran out of time on the last day with 114km to go 
so didn't see them...
So is the only thing I can do for now is just to spend more time in the saddle and wait for my body to adapt? I just can't help but snack quite frequently because I get tired.. I should eat more low glycemic index foods, think I ate majority high glycemic foods on that ride😅
