The FastDay Forum

Hi! I exercise three days a week, each for roughly 30 mins, pushing myself between 5 and 8 minutes of that time. At the end of it I am shattered but feel really good - and I am now fitter than I have ever been .
Yesterday, a feast day I did my usual swim, giving 8 out of 40 lengths my all. I was shattered, as usual, but even more so, and I landed up stuffing myself with nuts and raisins and biscuits afterwards as my blood sugar was so low. NOT GOOD! I know that I was hungry as my body is fasting (did my first two days fast Monday and Thursday) but it all seemed too extreme.
Any suggestions as to how to handle the shakes and physical exhaustion without smashing all that I've done earler in the week? What do you eat after serious exercise and how do you bring you blood sugar level up to a level that allows you to function? PS, I do not exercise this way on fast days. That would be too much!
PPS. I love this way of exercise as - like this diet - the pain is short but the effects long lasting!
PPS. Love the support and chat on this website. Thanks everyone!

I exercise on fast days, haven't had your experience. Outside fasting days, I often eat a small snack 1 hour before exercising - a small yoghurt and an apple, for example.
Raisins are excellent when I need extra energy fast, read a study recently saying they work just as well as the sports gels/drinks that are being sold for running etc. Banana's also contain a lot of sugar and potassium.
I would stick with the raisins and nuts, maybe a yoghurt, and give it some time. If your exercising after a fast day, consider a small snack before exercise?

Hi carolius, I am probably not the best person to advise but how long have you been following 5:2 for? I have found that even some exercise on a fast day is fine but I haven't normally pushed it as much as you (though I have played squash on occasion) and I have been on the diet for 7 months now.

I think there is a process of adaptation that marathon runners go through where their bodies can switch 'on the fly' to fat-burning from glycogen, doing 5:2 does seem to help our bodies do that (especially I suspect if you are 24-hour fasting i.e. eating all your 500 or 600 calories in the evening).

But if you are quite new to 5:2 it may be that your body is not making that switch so easily yet, so when your glycogen stores run low under intense exercise your body struggles to maintain the blood sugar levels. Continuing to push yourself in that situation doesn't sound like a good idea, but equally stopping and loading with sugars might not help the body's adaptation. I'm thinking aloud here as I don't really know and others can probably give you more expert advice.

Sounds a bit like overcompensating to me. Brain just caught you at a weak point. Probably even a small snack would have seen you right. It's probably not exactly low blood sugar, just the switch to burning fat that's the issue here.

Have a read of the FAQs. I think it's discussed in there.

I'd adjust to 5:2 over a period before doing high intensity exercise. I now have a watered down smoothie, do my exercise at lunchtime (about as high intensity as I can get) and then have my tea at 5. I have some nuts (like 6) if I need them but it's fine.

Just switch your routine around and be gentle with yourself until you're fully adapted.

[carorees]

Dominic is right that your muscles can easily burn fat but it takes a while (some weeks possibly into 5:2) for the body to become fat adapted. Going low carb helps.

Pushing yourself into the high intensity zone does leave you feeling shaky anyway I think until your body increases the muscle capacity to work by increasing mitochondria.

Also, swimming is known to give people the munchies! I saw a paper ages ago saying to be wary of recommending swimming for weight loss because it seems to generate more hunger, but also the cool water means you don't have the increase in metabolic rate for as long afterwards as you do with land based exercise. I love swimming so it didn't put me off but I'm careful to avoid eating afterwards.

I was shattered, as usual, but even more so, and I landed up stuffing myself with nuts and raisins and biscuits afterwards as my blood sugar was so low.

You measured it ? or this is a phrase you use to describe how you feel.

One thing I've found is that -surprisingly - it's easier to exercise hard the morning after a fast (ie no breakfast) than the previous evening. Just ran a 5k race, got a PB and felt great, though yesterday evening I was a little lethargic. I too think it does help to keep fast carbs to the absolute minimum (which I didn't yesterday, possibly causing the lethargy). It's as if the overnight period gives the body plenty of time to switch to fat burning.

Caroline is right, swimming is known to make you hungry, not sure that you had a real drop in blood glucose level. I have been exercising vigorously for years for 35-40 min 5-6 times a week, elliptical and jogging. I do it in the morning after a cup of coffee and a small snack ( a low carb muffin of 80 cals) A small portion of oatmeal ( porridge) will probably do the same trick. I do the same on fast and feed days and have never experienced anything like you.

HI - are you on any medications - as I changed to a different medication for a month of last year and in that month I shook if I didn't eat regularly - and in the end I completely over ate and put on almost 2 stone.... I came off that medication and with this WOE am now losing weight... The first fast seemed to work like a "reset" switch for me... I don't worry about shaking any more. I've burned 600 cals at the gym today - on a fast day and I've not eaten yet but I am not shaking.... I have rather large fat stores however...

Are you slim already? Because that could also have an impact... Also whether or not you are eating enough on your non-fast days...

[carorees]

I swam for an hour last fast day with no problems during or after the swim. I did my HIIT 5 min protocol the previous fast day and my legs felt shaky for an hour after...but they do that with HIIT on feed days too!

I'd agree with dominic and caro - that if you haven't been doing 5:2 for long, you might not flip that switch to fat burning. Give it another few weeks - perhaps if you are exercising on the day afterwards, have something handy to replenish with until you adapt. My PT swears by chocolate milk as having an ideal mix of protein/sugar to refuel with quickly.

I cycle 6 days a week and go to the gym for exercise classes 3-4 days of the week and, even on fast days, manage to get through a 60-90 minutes without keeling over.

As everybody says, you need to take it slowly but experiment and find what works for you....

I'm 11 weeks in and still adjusting/learning what works and what doesn't

Eg this week I fasted Tuesday and Thursday.... I did a 30 ish minute speed intervals run on Tuesday morning which was gone as I was burning off Monday's roast dinner....
I ran a short 3 miles Wednesday morning as it was day after a fast and that was ok too
Thursday I ran 7 miles in the morning - again, ok as I had a normal day Wednesday....
Friday I went out to run a steady 4 - 5 miles but it was hard and I ended up walking for a couple of 30 second blocks and struggled with energy levels

It was the cumulative effect of a good week if exercise plus day after a fast I think - I had also done a 2 mile walk each lunchtime too

I have been reading MFP as I currently logging everything (still need to do this to ensure my "portions" are realistic), and the other thing I have noticed is my weekly summary says I am only averaging around 10% of recommended iron levels so I am going to add in an iron supplement as that also has am impact on my breathing/asthma

I think that's due to eating veggie on 3 - 4 days a week whereas I used to eat meat pretty much every day - I have still got a lot to learn about the nutrient contents of foods and how to maximise my nutrients from allowed calories especially on fast days

Be kind to yourself, try varying intense exercise days and fasts till you find a good balance....

This was an interesting post. I exercise on fast days, and I try to work in a little bit of the high-intensity stuff into my workouts, but recently found out that I'm not getting the benefit that HIIT gives since I don't "shatter" myself like you are doing.

I was considering adding in a proper "shattering" HIIT routine at the end of my workouts, but given what you are saying, perhaps I should not do that on my fasting days.

One thing I'd say is that you shouldn't beat yourself up too much about the munchies in such a situation. It sounds like you didn't actually count the calories you stuffed into your face but rather that you let your "guilt" count them for you. Had you counted them, I'm guessing it wasn't nearly as bad as you think it was, especially if you took a week-long view of all of your calories consumed.