Fasted But Not Fast

Today marks four weeks after my Spring marathon in Manchester and I think this is the time to get back into some sort of structured (ish) training. I would have begun a little sooner, but I had my big two-day cycle ride last Thursday and Friday, so I needed to inverse taper on the bike.

High green hedges with blue skies above.
Walls of green

I’m still feeling some after effects of that ride – internal bruises in the palms of my hand when I try and go into plank, for example. But I managed a long, very slow, run today, averaging 13 minute miles for just over two hours, so that was pleasing.

It was slow, even for me, for two reasons. I still had the ride in my legs, and I wanted to explore running without eating anything first. As I’m a bit of a geek around books and research that is running related, I had read about the idea of running on empty, or ‘fasted running‘. By that I mean not having breakfast first (although I did have a couple of cups of tea with milk) and not having any gels en route.

The theory is that you can train your body to burn fat a little more efficiently if you don’t fill up your carbohydrate stores. You have almost limitless stores of fat, so you won’t run out or bonk, in the same way that you might if you ran out of your sugar (glycogen) reserves. I think this only works for endurance stuff, the kind of exercise where you’re able to breathe comfortably enough, as it’s a slower process to get energy out of fat rather than sugar.

Whether this is good or bad to do is not a blanket, one-size-fits-all thing. But I thought it was worth exploring for me because I want to reduce my reliance on gels, as I think they’re a bit artificial. I also want to reduce my carbs generally: not give them up, because I love bread/pasta/rice/croissants etc, but to reduce the portion of carbs I have with each meal. There are people on the extreme end of this debate, like Professor Tim Noakes (The Lore of Running), who think that virtually all carbs are evil, but there are quite a lot of other people, like Professor Tim Spector (main man in the ZOE Covid health studies), who think that generally, people in the UK and US eat more carbohydrates than they need, but that individually, some people are worse at absorbing carbs than others.

Not all the researchers in this field are called Tim, and there is a lot of research – sometimes with conflicting outcomes, so I think it’s important to be a bit wary of making radical changes. However, recently one of my sisters found that she was close to being diabetic, and physically, she’s way fitter than me and very slim. Apparently South Asians have more of a propensity to develop type 2 diabetes in the UK, six times according to this report but when you’ve tried to keep yourself fit and strong, it’s a bit of a bummer to still be at risk.

Therefore, I’m just exploring things in my own diet a little more. I love food, and I’m hoping that by reducing those carbs a little now, I won’t need to completely give them up in the future.

My fasted run went surprisingly well. For the most part, I didn’t feel hungry or lacking in energy. I did take a gel in the last half hour of my two hour run because my legs were starting to tire but, oddly, it felt like quite an intense sugar hit, and it doesn’t do that normally. This is one run, and the next might be completely different for a variety of reasons, but I will continue to experiment.

I’m not officially marathon training yet, so it’s a good time to try these things out. At the same, I want to get back to a nice base level of consistency so that when I do begin the training again, it’s not a shock to the system. I’m still deciding what that will look like, but I have a ball park of 25+ miles a week on a regular basis. That’s the plan anyway. It’s always hard to stay focused without a specific immediate game plan so I need to create a little bit of a goal, and that number is good enough for now.

6 thoughts on “Fasted But Not Fast”

  1. Yes I too often run 3m fasted and try to limit carbs/sugar which can increase dementia and cancer risk.
    I do wonder if running fasted brings you to ‘the wall’ sooner.
    I watched ‘Run Fatboy Run’ with Simon Pegg last week. Very funny.
    Apologies for missing zoom last night.
    I am looking forward to running the Thames Path again when I get back from the Camino.

  2. I love running on an empty stomach! I always fast with a black coffee. I do 16/8 I have more energy and perform well.
    However I did complete London to Paris bike ride and doing the miles I did I could not fast as needed much more energy as long days. Fasting is so good for us in so many ways x

    1. That’s interesting Nicola. I haven’t explored intermittent fasting but I tend to eat my tea early and mostly eat nothing after 7.30pm, so generally get around 13/14 hours food free. It’s definitely something that I will look at more.

  3. Great that you tried the fasted running Rita (although I suspect that even the milk in your tea gave you a little bit of sugar for your body to work on). If you want to know which carbs work best for you, maybe try the Zoe nutrition program, where you get personalised scores for all foods and lots of Tim Spector’s researched advice about stabilising blood sugar and much more. I’ve done it so if you want to know more, let me know. Rice, unfortunately, is not my best carb!

    1. Oh yes Heather. I have been looking at that, I want to try it. Was thinking the four month package. Been listening to the Zoe podcasts. Yes, the milk would add some sugar to my morning run but that’s okay. I’m not being ultra strict. I just wanted to see how I’d feel. Going to try it a bit more and see if I can keep it going for three+ hours.

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