Cardio exercise during a 45-hrs fast made me feel bad

(August) #1

I tried to google some of the points I want to bring up here, but I didn’t find what I was looking for. So, I’m turning to this forum to seek answers from people with more knowledge than myself.

Yesterday I started my 44-hrs fast. I had my last meal at 20.00 on Sunday, and the plan was to fast until Tuesday at 17.00. I’ve fasted this long before without any issues. I did this twice last week with 3 days in between to refuel my body. I did strength training and light cardio during both of the previous sessions of fasting. I felt good and didn’t really have any problems completing the fast as planned.

However, yesterday went different and I had to abort the fast last night at around midnight. Here is what happened:

At around 15.00 I did a 40 minute cardio exercise without any strength training. Heart rate was about 160 during the training. The type of training was sustained cardio. No HIIT. I felt fine, though the muscles in my legs were sore by the time I finished. Two times during yesterday I ingested high-quality sea salt to replenish my electrolytes.

At around 22.00 I started feeling very tired, so I went to bed. I all of a sudden felt really cold on my feet and hands, and even putting a warm waterbottle in bed with me didn’t help. Neither did taking a warm shower. I felt dizzy, and just generally like something wasn’t right. I tried for two hours to warm myself, but nothing helped.

So, I decided to abort the fast, and I ate some home-made, sugar free yoghurt with some chopped pecans. I had a small-ish piece of spiced Norwegian salmon (100 g). I also took 1 teaspoon of honey, thinking that I might have depleted my glycogen stored too much during the cardio, and the effects I was feeling might be related to that. Ingesting the sugar from the honey would help me get some fast carbs into my blood.

After feeding I could feel the warmth seeping back into my body for the next 45 minutes, and I fell asleep.

I am going to restart my fast today, but today I’m probably just going to skip training altogether, or I might go for a walk to get at least some extra fat burn into this fasting session.

I’m 43 years old, male, and have been pretty much constantly in ketosis since august 2021. I have gone from 114,5 kg in August to 90 kg which I weigh now. My guess is that my body fat percentage is around 22 or so (I have not measured this. Just eyeballing it based on previous experiences and looking at pictures).

What do you think happened to me last night? Thanks for any input and shedding light on this for me.

(Allie) #2

So don’t do it, it’s really that simple - don’t do anything while fasting that makes you feel bad.
When I was doing extended fasts my training was unaffected for the first 24 hours but beyond that, it wasn’t an option. You could try adding salt / plain unflavoured electrolytes in water to see if that helps as for many it will, but it’s very possible you just need to skip training during fasts.

(August) #3

Thanks. I kind of concluded that myself :wink: I won’t do cardio the same way I did yesterday. I was more interested in the biomechanical processes that happened to me. I seem to be quite okay doing resistance training, but that kind of cardio training I wont do again during a prolonged fast.

(Robin) #4

I think your body sent you a message. Not today.
Next week, it may say let’s go! But unless you are dealing with cravings, I have found it smart to follow my body’s lead.
Maybe you’ve reached a point where you can cruise for a while.

(Edith) #5

I think that doing your cardio with a heartrate of 160 was the problem. You are out of the fat burning zone and into the glycogen depleting zone at that point. I think if you want to do cardio while fasting you want to keep your heartrate in whatever the fat burning zone would be for you. This way your muscle glycogen will be spared and you won’t need to replenish it.

(Robin) #6

You are so smart!

(Bob M) #7

When I first started fasting 5+ years ago, I could fast 4.5-5.5 days and work out twice during that time. Now, I don’t attempt any workout when fasting that long. I’m not sure what happened, but I find it harder to fast just in general, and basically impossible to fast while exercising.

My rule of thumb was always, if I started to feel bad while fasting, I ended it. Hunger was not an ending problem. But the longest fast I did was 5.5 days, and I was aiming for 7. On day 5.5 (Saturday morning), I found I was getting dizzy when I stood up from sitting. I decided to end it. Feeling bad is not good.

(Robin) #8

What’s that called….?
Oh yeah, diminishing returns!

(Bob M) #9

Also, I’ve gotten thinner (well, except for my trial of The Croissant Diet, where I gained 20-25 pounds), more muscular, and exercise more. I’m up to 5 days/week of exercise, too: Sunday off; M/Tu workouts; We off; Th, F, Sat workouts. Harder to fast on that schedule.

By “fast”, I mean > 24 hours. I still don’t eat breakfast, though I also don’t quite make 16:8. Instead, more like 13:11. For instance, I ate this morning at about 10 am after my 1 hour abs/lower back/jogging workout between 6-7am. I won’t eat again until about 6:30pm, so that’s a break of about 7.5 hours between meals.

Sadly, I tend to eat too late. Will have one meal at 6:30pm, but tend to eat again at 8pm or later. From after dinner until then, I’m cleaning, taking care of my mom’s cats, getting ready for the next day, taking my daughter to dance or picking her up, etc.

(August) #10

Thanks everyone for sharing your knowledge :slight_smile:

I too guess it has something to do with the specific cardio I was doing on the first day of the fast. I had seen on some youtube channel (zero?) that this person always did glycogen-depleting cardio on the day of his fast, but perhaps I misunderstood, and he didn’t mean prolonged fasts.

I’m fascinated by the biomechanical stuff going on inside our bodies, and I realize after a few years that the topic of nutrition is actually still quite frontier stuff. The Zero youtube channel was talking about depleting the glukogen stores to heighten glukoneogenesis and fat metabolism.

My working theory after this “event” is that by doing cardio beyond the fat burning zone, I depleted my glukogen storage beyond what my body was able to replenish for its needs, and I probably got the cold hands and feet because of that and perhaps low blood pressure (I was generally cold as well). Eating some honey with yoghurt and a slice of salmon got my levels back up, but I still feel like ■■■■ the day after. Really lethargic. So, I decided to just eat normally today, and relax.

There is always tomorrow :slight_smile:

(Rebecca ) #11

I don’t do extended fast because I have never felt inclined to. One of the benefits to eating this way is I let my body decide
…something I hadn’t done for a long time!
I would agree that if you felt “off” while pushing yourself physically and not taking in sustenance, then it’s best to listen to your body!

(Robin) #12

Yes to all of that! Who knew our bodies were so smart! And that we could actually listen?!!

(Butter Withaspoon) #13

Your body could have rebelled against the 3rd 44 hour fast in 2 weeks. Even if you’ve managed that before sometimes the body has a stress response indicating that you’ve pushed too hard from too many directions. The exercise pushed you over this line I am guessing.

Great progress so far, you should be proud of your successes