How would you approach running during/after a 24-hour fast

Take a rest day. Stay up until midnight and eat a small meal. Go to sleep. Run your morning run but keep it easy. Then eat a nice meal with plenty of protein.

I have a lot of experience fasting and training. It usually take a full 24+ hours from when you break the fast to be back to your normal levels of hydration and energy. Therefore your best bet is to take off or run very very easy after breaking your fast. I'll usually run 9+ min pace either soon after I break the fast or the following day.

tfg6 wrote:

I have a lot of experience fasting and training. It usually take a full 24+ hours from when you break the fast to be back to your normal levels of hydration and energy. Therefore your best bet is to take off or run very very easy after breaking your fast. I'll usually run 9+ min pace either soon after I break the fast or the following day.

So for someone that usually runs around 6:15-6:45 minute pace, what speed should I strive for the day after the fast?

Everyone’s different, but I would regularly fast (once a week) for 40-45 hours (from dinner Wednesday to lunch Friday) to lose weight while maintaining 40-50 miles a week. I did not alter my training during the fast. 1 day of not eating is not that big of a deal (IMO).

I experimented with weekly 36hr fasts last year. I'd suggest waiting to break your fast after your run, because your body will be redirecting a ton of blood to your GI system after you eat. If you feel gassed, take a zero day, but you probably won't have any issues doing an easy run tomorrow AM.

Being fat adapted, I wouldn't have to change anything.

one day off won't slow you down!

TheXCrunner wrote:

one day off won't slow you down!

May turn into two though if I feel like crap the day after the fast

Just run baby don’t over think it

If your fasting is not a regular habit, it will be a lot harder on you than it is for regular fasters. Don't extend it by an extra 12 hours!

Eat a snack at midnight, go to bed, eat another breakfast snack, run. Make it a normal running day, but not an intense workout.

I fast periodically, and generally I'm fine the next day (with a meal the previous evening and breakfast that morning). But the one time I had a race the next day, I hit the wall 12 km into a 15 km race, saw my pace drop by 40 seconds/mile, and finished on shaky legs.

Just run easy. Go by feel. Do whatever you might on a rest day and enjoy it.

I’ve found that it takes about 3 straight days of fasting before I hit a wall energy-wise and have to stop running in earnest, but the longest I’ve fasted for is 10 days, so YMMV.

If you’re not used to running fasted you might get a little grumpy, but most people have plenty of glycogen for a run in the first 24hrs so you’re probably not going to die.

Historically speaking, not eating for a day isn’t unusual for humans and we are well adapted to it.