I’ve fasted – like, just water and vitamins – for a week before.
I found that I was hungry, especially for about the first two or three days, but that I mostly ignored it after that, though I did find myself paying more attention to food ads and stuff like that than normal.
I was significantly cooler. I assume that the metabolism cranks down. I needed to wear heavier clothing than normal to feel comfortable.
I felt like I had less energy to effortlessly run around. Like, I could get up and go somewhere, wasn’t weak, just felt more like something you’d think about doing before doing.
Don’t need to hit the toilet much. That’s neat. Do need to stay hydrated, which I found to be surprisingly easy to forget about without sitting down for a meal.
I wasn’t trying to push myself physically while doing that, though.
I’ve also tried running a long-run calorie deficit where I wasn’t fasting, but also wasn’t eating much – something like 500 calories a day or less – for a longer period of time, for months, and then did a ten mile bike ride a day – there are calories coming in, but they’re considerably less than what you’re burning just living. I found the biking to be kinda rough. It just yanked all of the sugar out of my blood. Had a couple times doing that when I had my vision start to gray out at the end of my ride, needed to stop and get my head down. Was kinda like a zombie after my ride for a bit. Also was colder, just as when fasting. While it’s doable – I lost a bunch of weight doing it – I have to say that I think that it was rather harder than just outright fasting and not doing the exercise. Every time I ate, I felt like it kicked me back into “being hungry mode”, and it was only really physically a strain during the bike ride.
I had a harder time mentally concentrating on things when I’m doing that. Haven’t tried quantifying it, but I’d say that I was less-productive while doing that.
Everything I’ve seen and read says exercise won’t actually change how many calories you burn in a day. It’s still super healthy to do, but does not replace a calorie deficit.
Your anecdote seems to support that. You burned up all your blood sugar by biking 10 miles and then almost passed out. So now you’re just going to laze around for hours burning fewer calories than you would have during that time had you not exercised.
I’ve dieted before and always embraced the “eat your exercise calories” idea. Exercise is good for your body, but any calories spent doing it should be eaten as extra food outside of your normal calorie goals.
My goodness this must be such an individual response because exercise is the only way I’ve been able to modify my weight downward, ever. Did fasting for health one year, 36 hours a week, no change in weight, did get lower cholesterol.
But start walking to work instead of driving? Weight drops. Stop walking the dogs at night? Weight creeps back up. My activity level seems to be the most important variable in my weight. Except for stress, which I don’t recommend as a weight loss strategy.
Interesting insight. If you were on a 500 calorie diet and “bonked” while cycling then presumably it was shortly after a meal, since at that level of calorie restriction you’re going to be running mostly on fat reserves directly rather than sugar via glycogen. It is absolutely possible to run marathons without having eating a gram of sugar. The advantage is precisely that you can’t hit a wall when the glycogen runs out. But apparently the keto diet is not quite as performant at the margin, which is why athletes haven’t all switched to it. It does deal with the hunger issue though, by all accounts.
I’ve fasted – like, just water and vitamins – for a week before.
I found that I was hungry, especially for about the first two or three days, but that I mostly ignored it after that, though I did find myself paying more attention to food ads and stuff like that than normal.
I was significantly cooler. I assume that the metabolism cranks down. I needed to wear heavier clothing than normal to feel comfortable.
I felt like I had less energy to effortlessly run around. Like, I could get up and go somewhere, wasn’t weak, just felt more like something you’d think about doing before doing.
Don’t need to hit the toilet much. That’s neat. Do need to stay hydrated, which I found to be surprisingly easy to forget about without sitting down for a meal.
I wasn’t trying to push myself physically while doing that, though.
I’ve also tried running a long-run calorie deficit where I wasn’t fasting, but also wasn’t eating much – something like 500 calories a day or less – for a longer period of time, for months, and then did a ten mile bike ride a day – there are calories coming in, but they’re considerably less than what you’re burning just living. I found the biking to be kinda rough. It just yanked all of the sugar out of my blood. Had a couple times doing that when I had my vision start to gray out at the end of my ride, needed to stop and get my head down. Was kinda like a zombie after my ride for a bit. Also was colder, just as when fasting. While it’s doable – I lost a bunch of weight doing it – I have to say that I think that it was rather harder than just outright fasting and not doing the exercise. Every time I ate, I felt like it kicked me back into “being hungry mode”, and it was only really physically a strain during the bike ride.
I had a harder time mentally concentrating on things when I’m doing that. Haven’t tried quantifying it, but I’d say that I was less-productive while doing that.
Everything I’ve seen and read says exercise won’t actually change how many calories you burn in a day. It’s still super healthy to do, but does not replace a calorie deficit.
Your anecdote seems to support that. You burned up all your blood sugar by biking 10 miles and then almost passed out. So now you’re just going to laze around for hours burning fewer calories than you would have during that time had you not exercised.
I’ve dieted before and always embraced the “eat your exercise calories” idea. Exercise is good for your body, but any calories spent doing it should be eaten as extra food outside of your normal calorie goals.
My goodness this must be such an individual response because exercise is the only way I’ve been able to modify my weight downward, ever. Did fasting for health one year, 36 hours a week, no change in weight, did get lower cholesterol.
But start walking to work instead of driving? Weight drops. Stop walking the dogs at night? Weight creeps back up. My activity level seems to be the most important variable in my weight. Except for stress, which I don’t recommend as a weight loss strategy.
Interesting insight. If you were on a 500 calorie diet and “bonked” while cycling then presumably it was shortly after a meal, since at that level of calorie restriction you’re going to be running mostly on fat reserves directly rather than sugar via glycogen. It is absolutely possible to run marathons without having eating a gram of sugar. The advantage is precisely that you can’t hit a wall when the glycogen runs out. But apparently the keto diet is not quite as performant at the margin, which is why athletes haven’t all switched to it. It does deal with the hunger issue though, by all accounts.