Water Fasting : the next day
 

There is one thing about fasting metabolism that i don't understand.
If i don't eat anything, i can ride the whole day and never feel tired. My energy levels even peak in the evening on my way back home. I commute 90 km for 3.5 to 4 hours.
When i get back home, i eat a lot.
The next day however, i feel very tired and i can't ride fasted.
How does the metabolism work so it prevents me from fasting the next day ?

Any time you do more physically than the norm, you need at least one day of recovery at less than normal exertion levels. Exercise, nutrition, rest and recovery is the only path to increase physical ability.

All animals rest while digesting a large meal. Your body needs to digest and recover after exercise and a large meal.

Not certain why you find it odd that you could ride a bike for 4 hours and not need anything. That's still way less than a pound of body fat.

I might suppose you didn't drink enough water if you were tired the next day. That was something you do often wasn't it? If you only ride that long ride infrequently then it might be your body just needing to adjust to the unexpected.

​​​You are right ​​​RH Clark , but i'm not an occasional rider and i can ride the whole week when i don't fast.
That's one plausible explanation, so you think that my body continues to digest into the next day and that's what keeps my energy low?
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​​yep ​​Iride01 , i have tried it several times and it's always the same, and i drink a lot so hydration is not related. Whenever i fast the next day i feel very tired the next day.

When I raced many moons ago, I read a book "food for Fitness" (Rodale Press ~1970) that talked extensively about the ease of digestion of various food types. Also that protein, while essential, is not needed beyond a rather small amount in an endurance athlete. That protein is the hardest of the food types to digest. Based on that, I stopped eating meat. Happened upon yogurt and instantly felt so much better than after the milk and cereal I ate my entire life that I stopped all un-cultured milk products. (Not diagnosed but I am certain I'm mildly lactose intolerant.) Tried to limit high protein sources. (That was touch because I live sharp cheddar cheese! But I cut out cheese 7 years ago along with all other diary and instant;y felt much better.) Cut down on salt radically and white sugar entirely also based on that book.

What I found was my recovery after hard rides was far better when I ate easy to digest meals afterwards. Slept better and recovered more after dinner of beans, fresh veggies and whole grains than I ever had eating meat. The low salt meant that on the hot and humid days, I sweated out far less sodium. The very hot races I rode above my class, simply because I slowed less. (And since I had no tolerance at all, white sugar and caffeine were pure drugs. Admit to being guilty of using them in races and on very long, hard rides when I found myself bonking 50 miles from home. (A cup of coffee with two cubes - getting home was easy!)

Your ride intensity might have something to do with it. If you are going at it hard the first day, you might be depleting your energy reserves for quick energy. Depending on what your diet is after you get back from the ride, you might not be getting enough to replete that stored quick energy. If all you are going to take with you is water then go easy on all your rides till your body gets use to that new norm. Then find out how hard you can go.

Interesting book, as the common wisdom is that endurance athletes in training need a considerable amount of protein, up to 0.9 grams per pound of body mass per day. For a 150-lb cyclist, that amounts to about 135 grams, or 540 Calories of protein. That's about 46 ounces of Greek yogurt (doesn't seem like a "small amount").

Fatigue -- boy I don't know!

Fatigue: it's a feedback system that prevents us from exercising to death. It's mysterious and poorly understood.

Even a mouthwash of sugary liquid can improve performance. So why not a feedback that says "hey, if you're going to exercise without eating, I'm going to make you slow down"?

I've had a lot of personal experience in fasting and cycling while fasting and only eating during a short window after a ride. Like you I always had great energy until I ate. That is except for one time when I bonked hard about 35 miles into a ride after having fasted more than 24 hours. I just think when you burn up all the glycogen stores in the muscle, it takes a while to build it back up, especially if you consume low glycemic foods when you do break the fast. I think digestion can cause low energy, just depending on how much you eat and how quickly that type food digests. I would suppose your low energy is more about building back stores of energy and possibly even repairing and rebuilding tissue.

Are you saying that the main fuel one burns when fasted is muscle glycogen ?
I have always attributed those fasting energy levels to ketosis. From what i have read, fasting enables our bodies to use fat as the primary source of energy, but glycogen stores in the liver must be depleted first. Haven't read anything about muscle glycogen, though.

good advice, i am vegan so i wouldn't attribute that fatigue to what i eat, but the quantity might be a clue. I usually eat a lot when i get back at night.
What was the benefit of cutting out on salt?

That's not really a very large amount of protein. Maybe for someone fasting over multiple days. But for those of us eating three squares it's not really a lot.

But the bigger thing is that just because we sometimes do an occasional long distance ride, I don't think that makes us the endurance athlete that the study was talking about. So we, or at least me doesn't need that much protein.

Now if you regularly ride 400 miles a week, then you are probably that person. However I only do 80 - 125 miles per week with very rare week of 200 miles cropping up occasionally. So I'm definitely not that person described for that study.

Absolutely, but this is not my first experience with fasting. For 4 years i have been doing this (90km commute and fasting) mainly because i don't have to worry about hitting the wall on my way back home (which does happen when i don't fast and forget to eat lunch)

When you say fasting, is that just for the ride or are you fasting for a certain part of the day or what?

It means no breakfast, ride 45km, skip lunch, ride back home and eat dinner.

that's a funny way to put it, but i'm not talking about exercising to death. I'm talking about my daily commutes and i can't afford to put more effort than necessary. So my heart rate is mostly zone 2-3.
Besides, seems like evolution shaoed our organisms to be optimised to use fat as their primary source of energy for long periods of food scarcity :

I do similar stuff, but not in the strict context of fasting. I might have a piece of fruit or something small at some point before the ride starts. And although normally I'll have a small bowl or cereal or oatmeal prior to a 100 km ride, last few I've done were on an empty stomach. Though during the ride I'll sometimes get a banana or cookie at the stops. And I always have 120 to 180 Calories sometimes more carbs in my bottles.

So if you feel you are tired the next day, maybe you just rode too hard and depleted your reserves, though usaully I feel that if I'm tired for an extended period of time after hard activity, then it's usually I hydrated poorly. I've sometimes weighed before and after a ride. When I was regularly losing 3 or more pounds (1.3 kilogram) of weight, then my energy levels did take more time to recover. Today I can go on a 62 mile, (100km) ride and not lose any weight at all since I hydrate well. And I don't feel tired that evening or the next day. In fact, just give me 20 minutes and I'm ready to go.

That might be controversial as some think that maintaining your water weight is detrimental to performance. However it hasn't seemed to for me. But I'm not that big into one day of performance. I'd rather be able to perform multiple days in a row.

Tired is one thing, but if you feel fatigued then something else might be needing a doctors opinion.

The body needs salt in the system as an agent to make things work. (Sorry, no formal background here at all.) Less salt than that amount and the body suffers. Now the body uses salt but it does not break down salt. So the salt you eat must be eliminated. It works to eliminate the excess by adding it to urine and sweat. But the body does not have a "saltometer" (equivalent of thermometer) that works in real time. All it can do is say that since you regularly intake X amount of salt, it needs to add Y percent of salt into urine and sweat. That works fine on most days but that day you sweat 2 gallons of Y% sweat, you have just emptied your body's salt reserve. Crash time! So the bike rider who regularly eats X salt per day needs to replace a lot of salt on the hot day.

But suppose you eat far less salt every day, like say half? X/2. Well, the body adjusts and just puts Y/2 percent salt in your sweat. Same two gallons of sweat? You just lost and need to replace half as much. Now, this reset of our "saltometers" takes a lot of time. I started in the winter of my big racing year. Shot for no more that 1000mg/day. By summer, my sweat no longer stung when it got in my eyes. I never saw traces of salt on my jersey, even on the hottest and driest days. My clothes felt better after riding. The low salt regime was tough at first but it got easier. Salted foods started tasting too salty. I started seeing how incredibly much salt we eat in this country. It is everywhere. I only did this rigorously for one year but the results were striking. And what a boost in hot weather races!

In the third world there are countries where salt is scarce enough and expensive enough that only the wealthy can afford to buy it and salt their food. The rest simply don't. And do just fine. But if one of us goes to visit those of the working class, we'd better bring salt or we're heading for trouble! And the wealthy make it a point not to eat their food. Class, etc. yes, but also they'd keel over like us.

I've been a lacto-pisco-vegetarian for 50 years. You need protein. I've been taking 30g-45g of a high-quality whey protein for decades. I've experimented with running that quantity up and down over the years and this quantity for a 145 lb. guy coupled with high quality grains, veggies, etc., works for me. (Older athletes need more, though that's not been well investigated.) Less does not work. On a too-low protein diet you'll feel fine for a while, but you'll eventually notice that your muscles aren't recovering like they used to. On an unnecessarily high protein diet you'll feel fine. It's not the protein in the meat that's the problem, it's the fat and all the rest of the feed-lot garbage that causes problems. If you are a hunter and are eating your own game, meat is not an issue as long as you're getting plenty of carbs, fruit, and veggies.

Terrymorse is correct. I wouldn't take for fact anything you read from Rodale Press. Depending on age, an endurance athlete needs anywhere from 1 to 2 grams of protein per kilo of bodyweight. The problem with a diet like mine is that it's almost impossible to figure the daily protein intake for a varied diet, so I had to experiment to see what worked for me.
https://www.ncbi.nlm.nih.gov/pmc/art...cise%20%5B4%5D.

Like I said, Rodale is BS.

For the OP, riding fasted depletes you. Simple as that. It's all take-away and no put-back. A riding buddy of mine spent some time in India, where like much of the population, he picked up the habit of fasting one day a week. When he came back here and started riding again, he too was puzzled about his low energy for the 2 days following his fast. That meant he couldn't train as hard as he was used to doing and was gradually getting weaker. I got him to quit the fasting and his energy and training came right back no problem.

I'm Jewish and fasting on Yom Kippur, even though it's only from the end of one dinner to the start of the next, is a significant burden which has to be made up for nutritionally. And I definitely don't exercise on YK!

Yup, I read that the muscles will first look for glycogen or fat, else it will get into protein-burning mode which bad because you need protein for recovery and strengthening the muscles.

The Muslims have a similar fast and during Ramadan just before dinner, everyone rushes to the grocery stores hoarding every food on the shelves! They don't seem to lose weight on the 30-day fast so I suppose they make it all up from 6pm to 12am. Although Ramadan gives you 6 hours to eat, allowing some workout sessions within that time as well. However, I doubt hard workout sessions would be possible.

I'll stick with Pritikin. Its nothing radical or complicated, and it works. https://www.webmd.com/diet/a-z/pritikin-diet

Pisco vegatarian!? Interesting food choice I've never seen associated with vegetarians. Though I'm sure some vegetarians do also partake! <grin>

Yeah, there are a lot of us. Otherwise no one will invite you to dinner. At home, we eat some fish, not a lot. I'd like to eat more wild caught salmon, but it's too expensive. We never eat the farmed stuff. A friend took us prawn "fishing" the other day. Fun, and we got 80 nice prawns in the freezer, probably a year's supply.