Fasting as a Runner

This topic contains 6 replies, has 4 voices, and was last updated by RunnerRach 8 years, 11 months ago.

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RunnerRach

9:29 am
15 Jan 16
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Hi everyone, just introducing myself, Im Rachel 43, married mother of 2 teens, runner, cardiac nurse. I have always had a tendency to be ‘weighty’, but have successfully managed to keep my weight down with running and eating fairly healthily over the last 12 years or so, my weight does yo yo as I tend to be a bit of an emotional eater (I gorge when stressed).

Anyway, 6 months ago I started a new job where I am not as physically active at work and temptation is thrown in my way every day due to reps bringing food in, added to the fact Im not running as much as I am at work more and I have gained a stone.

I’ve been thinking of doing this for a while as I watched the programme when it was on TV a couple of years back and am impressed by the science behind it. As a scientist, and a nurse, everything I do at work is evidence based so this seems to be the ideal thing for me.

My main concern is my running and this is what has put me off before, I run on averag 5 miles at a time but my long runs up to 12 miles 3-4 times a week, there is absolutely no way I can run even 5 miles if I was fasting. However, a colleague at work who is a runner does intermittent fasting and after speaking to her about it I’m thinking of giving it a go, fasting on 2 of the days I’m a work and running at home in the morning after a fast day while I’ve still got the energy from the calories eaten the day before.

Has anyone else got anymore tips for me?

Amazon

10:29 am
15 Jan 16
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Hi,

What time of day do you usually run, and do you eat beforehand?

I don’t understand why you can’t run on a fast day. The whole point of fasting for weight loss is to make the body burn fat for energy as there is no food to use. Have you tried it or are you just worried that you won’t be able to do it?
I never eat before exercising and often spend an hour doing cardio in the gym followed by a 30 minute swim on the morning after a fast day and I don’t have any issues doing so.

Nama

12:06 pm
15 Jan 16
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Hi Rach,
Just to reinforce Amazon’s comments…once you get used to fasting, you will have no trouble doing any strenuous exercise whilst fasting. I swim laps 3 times a week, on the days I fast. It took me a while to have the confidence/belief this was ok, but I think your metabolism gets used to the fasting after a month or so and you body gets quicker at adapting to no food. Many of us actually feel more energised the days we fast. I think you will find that its more what you eat than the calories you burn with exercise that will help you become master of your weight. The exercise is great but I believe its’ main benefit is the ‘feel good’ factor (endorphins?) and the motivation to continue on a healthy path! Good Luck!

HappyNow

12:08 pm
15 Jan 16
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My understanding is that endurance exercise is better fuelled by fat than glucose, but that you need to be adapted to burn fat (i.e. have been on a LCHF diet to make the switch). You will not make a quick switch from using glucose to using fat on a fast day during exercise, if on non-fast days you are not low carb/low sugar.

I run (only 4ish miles 3 times a week, and not in the depths of winter!) but I struggle with running on fast days. I don’t temperature regulate as well, and feel weaker and light-headed. While I eat very little processed carb and added sugar during the week, I am not strictly LCHF and am therefore not fat-adapted.

Amazon,

I’m guessing that you must have sufficient glucose/glycogen for your exercise sessions, which is why you suffer no ill effects? But you might find during higher intensity and longer duration exercise (i.e. distance running/ cycling) that you did deplete glycogen and ‘bonk’?

Amazon

12:27 pm
15 Jan 16
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Hi Happy,

I have no idea why I’m OK when I go to the gym. It was tough when I first started and I put it down to being new to the gym rather than the effects of fasting but with hindsight it could easily have been a combination of both.
I’m doing 15 minutes on the rowing machine followed by 15 on the bike which includes several episodes of HIT followed by 30 minutes on the treadmill walking as fast as I can. I want to give running a go but am not sure if my knee will like it. There’s only one way to find out……

Apologies Rachel, none of this helps you does it?
I guess the advice your running friend has given you plus the tips from Happy regarding what you eat are the way to go.

Good luck.

HappyNow

12:40 pm
15 Jan 16
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I think there is a difference between exercising in the morning of a fast day (or even the morning after), when you have eaten the night before, and exercising in a truly fasted state (reserves fully depleted).

I tend to run in the evening, so on a fast day this would be perhaps 22 hours from my last proper meal (and more than 22 hours since I ate any significant amount of carbohydrate). Perhaps this is why I struggle!

I’ve just found the following link which may be useful and suggests that the demands of Rach’s running regime are likely to be considerably higher than for most people!

http://www.runnersworld.com/ask-coach-jenny/should-you-try-fasting-before-running

This suggests that it doesn’t necessarily work for everyone, and you’ll need to experiment to find out what works for you.

RunnerRach

2:59 pm
16 Jan 16
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Hi again, thanks for the comments, to our it into perspective, even when I have been ‘dieting’ before and not in a fasted state, it has a significant effect on my running performance in that I feel sluggish, weak and am either slower or find the run harder, for instance today I went for a 5 mile run at 11am, I had nothing to eat this morning at all beforehand but afterwards, felt shaky and ready for my lunch. If this has been a fasting day I just wouldn’t have been able to function.

I do normally run in the morning (usually earlier than this)