Be sure to know what a “Complex Carbohydrate” really is. It doesn’t mean long-chain starches. Those are still sugar. A baked potato, bowl of white rice, a slice of bread, and even corn on the cob are just fast-acting sugars to the body. In fact, they all have a higher glycemic index than table sugar (except some low-carb breads such as Ezekiel bread).
“Complex” means trapped inside of other things. So, an apple is complex. Broccoli is complex. Kale is complex. Peppers, asparagus, etc. You have to chew it, and it has fiber that hasn’t been milled in a factory.
Not apple juice, or any type of juice. As soon as you juice or puree something, even if you “leave the pulp in”, it’s no longer complex. The body no longer has to wait to absorb the calories out of it.
Sitting at a desk, you need about 0.4 kcalories per pound per hour. There is no need to eat anything starchy or sugary. It is turned into glucose before it enters the blood stream, and it only has a half-life of 15 minutes. Anything you didn’t burn in an hour will be turned to fat. Most sugars other than glucose, including half of table sugar, is sent to the liver, converted to glucose, and only about 10% of it makes it into the blood before being turned into fat.
If you’re exercising for 2 hours, you should be able to fuel that with reserves, even at maximum effort. The key is to keep your water and mineral levels happy (20-30oz per hour, with a gram of salt mixed in, and whatever else you want to flavor it). If you want to eat, eat whatever you can stomach.
However, if you’re exercising hard for 5 hours, there is no reason to eat fresh vegetables during your workout. You should have done so before, and will do so after, because of the vitamins and minerals. Those are just too slow to provide your energy needs during cardio.
Exercising at maximum effort, you need about 4 kcalories per pound per hour, plus water and extra minerals. At sustainable effort, you need 3kcal/pound. A tablespoon of corn syrup (not HFCS) washed down with water is almost exactly what you want. (2mg magnesium, 4mg calcium, 9mg potassium, 31mg sodium, 16g glucose, 57 kcal).
Even if you stop for an hour in the middle, you’re still running 30% over idle. If you don’t supplement during the exercise, even with a meal break in the middle, you’ll run out of energy. This will feel like you’re too tired to go on, and if you’re measuring, you’ll lose 30% or more of your peak effort. The refill rate is 3x longer than the burn rate, so once this happens, it’s too late to come back.
Ultra-athletes can double this reserve, and improve their ability to burn fat to extend their peak efforts. Also, their peak efforts move further up, so they can operate at a lower percentage of peak, meaning they can refuel a higher percentage of their reserve consumption during the workout.
Even so, even the best athlete will eventually run out of glycogen reserves. They just have learned how to keep going at this point. They’ve killed off the muscle cells that can’t handle it, and walled off the parts of the brain that tell them they are too tired to continue (fatigue is mostly in the mind if your hydration and electrolytes are okay).
Proof? Look up ultracycling mph ranges. 7hour riders might be in the 17mph range, 12 hour rides in the 16mph range, and 2.5 day rides in the 13.5mph range. Many of these riders can easily average 20mph for 2-3 hour rides, and push 22mph averages for hard workout days. These stats do not subtract rest stops.
Comparatively, my non-athlete speeds, and I did 40mi at 14.8mph, 23mi at 16.3mph, and I can easily hit 18-20mph on flats, even 34mph on a downhill if I don’t have far to go. I *do* subtract out rest stops.