Riding While Fasted - Interesting Observation

(Central Florida Bob ) #1

I’m not sure if I should post this here or in the Extended Fasting forum, but for the last few weeks I’ve been doing another N=1 experiment on myself.

Before the experiment, my “control” was to do my three rides a week at about the 38th hour of a 40 or 42 hour fast. I do alternate day fasts three days a week (Sun, Tues, Thurs) and eat four days a week. My rides were on eating days, before my meal.

Over the last few weeks, I’d noticed a tendency to get cold hands and feet, along with feeling cold in the house. This is Florida, and while it’s not as hot as it was in August, we haven’t had any real cool weather. We’ve had two nights where it dipped under 70. My wife commented on the cold hands a few times, but it was easy to brush it off thinking, “I’m fine, I just had my hands in cold water”.

The experiment was to bring the ride forward 24 hours to the first fasting day, about 14 or 15 hours since my last meal. With six days of riding earlier, I’ve noticed on at least five out of six that the cold hands have disappeared. On the sixth day, I’m not sure. I’d say less cold than they had been.

Here’s the catch. I don’t actually know what’s different and if it’s good, bad or just doesn’t matter.

I do the same amount of riding (about an hour on the road - 13 to 18 miles, depending on what I feel like doing) and I don’t believe I’ve altered my eating. I’m eating to satiety, not measuring grams of food. According to a calculator I’ve played with, the amount of fat I have available to burn, and using Richard’s 31.5 calories per pound of body fat per day, it tells me I can’t produce the energy I need to burn for minimal, sedentary activity - not even counting the ride. According to that my fat can produce 1000 calories less per day than I was burning, not counting the ride which adds another 500 to 600 calories.

That might imply I was going into starvation mode before and conserving energy, but that doesn’t explain why burning those calories 24 hours earlier would get rid of the shutdown.

It might also be telling me I need to get some fat calories while otherwise fasting.

Help: Fasting and Lifting Question?
(Bob M) #2

I’ve noticed something similar. Even though I love higher protein, I need higher calories and even – gasp! – fat to delay/stop the cold feeling. I usually workout after my first day of fasting (so, about 32 hours into a fast, on Tuesday after fasting Monday). I usually last 36+ hours, then eat. I’ve tried really hard to hit a second 36 hour fast on Wednesday, but make it only 22 hours at best. I get too cold.

I’ve also found (by accident) that eating fat causes me to be warm.

There’s a theory that protein is harder to access as an energy source, and that fat is our energy source. So, I generally eat higher protein (particularly after exercising), but before I know I’m going to fast, I try to eat more fat (and calories) if I can (and can force myself to do so).

(Eric - The patient needs to be patient!) #3

I tend to eat more fat the last meal before fasting. And I still get cold at 24+ hours. Humm - much to ponder. I hope the cold is not starvation mode. I don’t want my BMR to go down.

(Central Florida Bob ) #4

I used to joke that I pay far too much money for the privilege of being cold - if I can even get to that point. If I can get cold at all running the air conditioner. With fasting, I can get cold for free. I even save money by not eating or setting the air lower, so fasting pays me to get cold! :crazy_face:

Maybe this is an argument for a fat bomb on fasting days? Richard’s page on why fasting is easier for some people includes a calculator to tell you how much fat you need to add.

Psychologically, I’m not having an easy time thinking I might be too thin for something, and this is saying too thin for riding while fasted. Me being too thin for something hasn’t happened in nearly 60 years.

(Bob M) #5

@daddyoh Try eating higher fat, higher calories for a day or two before fasting. See how that is. Report back (I’d be interested).

@CFLBob and @daddyoh It’s tough to determine what the cold is. I’ve done research, and some say it’s BMR going down, others seem to say it’s a natural effect of fasting (the body’s trying to keep the blood where it’s important and not send it to the extremities). It would be nice if there were a way to test these. For me, I also take carvedilol (a beta blocker), which by itself is known to cause cold extremities.

For my money, I’m betting it’s our body’s way of telling us we’re doing too much fasting (whether that also means lowered BMR, I’m not sure). I say this only because I was getting so cold while fasting, I had to stop. After a respite, I started again, and wasn’t cold anymore. And if I take a longer break between fasts, I can delay getting cold even until the second or third day of fasting. On the other hand, if I try to do “too much” fasting too close together, I get too cold too quickly. If I start out fasting and I’m cold before 11am, I will “fail” for that fast. If, however, I start fasting and don’t get cold the first day or the first day until I go to bed, I will make my fast.

Although if you’re in Florida and getting cold…that’s an issue. :wink: But you get used to your environment. When I was in AZ, people who had been there a while would be wearing jackets and gloves when it was like 60 out. We went there in February one year (from CT), and I had a sweater on in the morning, and it was brutally hot after about 8am…to someone who keeps their house in the lower 60s during the winter. To them, it was cold.

(Susan) #6

Some people do Fat Fasts – have you heard about this?

@David_Stilley has done a few of them and he has lost weight doing them.

Dr. Jason Fung’s video on Autophagy talks about Fat Fasts as well. I think it is in this video where he discusses this (I cannot check the video atm but hopefully David will see this and weigh in on it! He knows a lot more of the specifics/science about it then me!

(Central Florida Bob ) #7

Isn’t that saying the same thing? I mean keeping the blood in the core seems like the body is saying, “it’s a crisis! Screw the hands and feet, we can get by without them!”

I sure do wish I had some good measured data on this.

(Central Florida Bob ) #8

I have, I just haven’t put any thought into doing one, taking the idea that any calories break a fast. I think Carl would say “it’s not a Fat Fast, because you’re eating”. You’re just eating only Fat. OTOH, I usually allow up to 400 calories from fat on a fasting day, an idea I got from Dr. Fung or Megan. Two teaspoons of HWC in the two mugs of morning coffee and a teaspoon or two of butter in the evening (to help some with some meds and supplements I take daily).

I used to like these fat bombs a couple of years ago (last time I made some):

Maybe I’ll make up a batch and try a couple a day. If you divide those ingredients into 24 servings, like recipe says, that’ll be about 70 calories each, with <1 g carb and <1 g protein.


I don’t know about getting cold as I’ve not noticed any of that but I know the 2 Dudes and I think Phinney and Volek talk about only being able to access ‘x’ amount of body fat per day but I don’t see how that can be right. I have done a run 12/13 hours fasted that has lasted nearly 4 hours and not run out of energy. According to my garmin I burned 2000 calories with that run. Today I ran for just over an hour 37 hours into a fast. Haven’t particularly fuelled any specific way before my runs or fasts.

(Central Florida Bob ) #10

Richard Morris used to talk about a paper he saw that said we get 31.5 calories per pound of fat per day. (that’s in my second post, above) I’m suspicious of “one size fits all” numbers that work for a 4’10" tall woman or a 300 lb NFL lineman, but it’s where I get that I can produce about a thousand calories less than “sedentary” on that calculator, not including the ride.

I don’t have issues with feeling like low energy while on the bike or not being able to produce power, only the cold fingers several hours after the ride. Like 10 or 12 hours after the ride.


I’ll pay more attention several hours after then, next time I do a longer fast and then run