I find I can run on a fast day, BUT running the day after a fast day is difficult. I want to move, but I feel like I’m a 100 years old (even with some food in me to break my fast). Maybe it’s just me, but thought I’d comment so that if someone else is experiencing this effect they might have some insights into how to get around it.

I was dubious too, but ran 4/5 miles a couple of weeks ago on a fast day and was fine. Planning to do some lengths in the pool tomorrow am in this heat as I’ve run 10k today.

Hi I’m 2 weeks into the 5:2 but would like to fast on my running days as those are the days I eat separately from the family anyway. I run with an evening running group so will not be eating my evening meal till 9pm (probably a soup) for ease, don’t think I could manage breakfast at 9am then nothing till after my run at night. Any suggestions how to work this?

Thanks rockyromero. Decided I’m going to skip breakfast and eat something pre-run instead so banana sounds like a good idea tho will need to make it into a smoothie as its the only way I can eat banana! Hopefully have better luck this next few weeks as I seem to be taking off and putting on the same few pounds so far, probably because I am starving and definitely eating more carbs than I should on non-fast days. Determined to crack this though.

Hey Rogw, I was wondering whether you getting so exhausted was simply because your liver ran out of glycogen and you turned to fat burning? This is known as hitting the wall and can provide those symptoms I think.

Just my two cents ^^

I have done a bit of running on fast days and felt fine. So far I haven’t run the day after, instead doing weight training (like today; fasted yesterday, lifted today. Then ate some cake).

I didn’t find any drop in my ability in the gym due to fasting yesterday. If I run after a fast day soon I’ll come back to this thread and post my findings!

I’m faster on fasting days and as long as its under 2 hours I don’t really notice any down side. Above 2 hours and I really start to run out of steam.

The only thing I would say, is if you train against zones e.g. intervals or HITs then you need to take account of your probably lower HR on fasting days.

I need to take at least 10bpm off each zone max. I think its probably reasonable to ignore the cals burned reduction on fasting too as this is usually a factor of HR & time.

I generally find I have a lack of go in me on the following eat day. Its the same as having a huge lunch and then expecting to train hard in the early evening.

I run almost every day, and I have no problem working out on my fasting days. However, I am very slow and tired on the day after a fast. Maybe my body is too depleted by that point. I try not to schedule long runs or races on the day after a fast. If possible, I make them rest days.

Hi ,

I run 5k’s and am finding. My times improving with the weight loss. I can and do run on fast days, Monday’s and Wednesday’s but find it harder on the 2nd fast day.

Good luck everyone

F

Is there any evidence to back up the (apparent) consensus here that exercising in a fast day is fine; but exercising the day after a fast day is a struggle? I am just starting out on the 5:2 regime and am trying to work out which days to fast. Every Saturday and Sunday I cycle for 80k. On Monday mornings and Wednesday evenings I swim 1.5k followed by 5k runs. My preference – simply on social grounds – would be to fast on Fridays and Sundays, but I’m concerned that will just exhaust me. Can anyone advise me on a strategy? Thanks.

6 weeks into 5:2 on ketogenic diet, and have to say i can excercise after a fast day

Perhaps becasue i have been keto adapted athlete for a good couple of years possibly(?)

i’m good for high intensity running for at least a couple of miles. I was working on the hypothesis that as there were super low levels of insulin at this point it had enabled my fat burning to be ramped up higher than normal.

The first time i managed 5 miles fast and appeared barely out of breath.

I repeated this for a 10k race a week later but there must have been something i was missing as i only lasted a couple before dying a death. All i can think of was that i had eaten a lot the day before the fast day the first time

Raced a half marathon yesterday using my old favourite protocol of carb loading and suplement with gels during race but this is playing havoc with my digestion… it appears as i have been ketogenic for so long i can no longer tolerate carbs to barely any degree. I feel nauseous & get terrible brain fog.

i love racing and started all this to race better marathons but it appears i need to introducce carbs back in for the high intensity endurance or forget racing and continue to enjoy the stable keto way of eating… any ideas???

loving the 5:2 diet… is it still called that if i’m ketogenic

peace