A week of intermittent fasting


4 minute read

Experimentation 🧪

I do a lot of little experiments in life to see how I can optimise and improve my productivity, wellness, discipline, lifestyle, relationships, diet, and training.

Previous mini social experiments I’ve tried on myself are:

  • A vegan diet for a month - I ended up sticking to this except the occasional cheese and chocolate - now I’m trying to keep it fully.
  • Becoming minimal - recording every item I used and purging quite a lot of them afterwards.
  • Tracked every calorie I ate for a month - and longer.
  • Didn’t use social media for 30 days - I’m back on it now.
  • Quit alcohol for a month - and longer.
  • Quit coffee for a month - I lasted 2 weeks.
  • Ran every day for a month - more on that in a later article.

Only a week!?

I do most of my experiments for 30 days to get a clear result and ingrain a habit. This time I tried intermittent fasting for only a week.

Why a week? - I thought I’d be pretty hungry by then.

No, it’s mainly because I’m due to start marathon training soon so I don’t want to be doing too much at once. Starting an intense training plan as well as a new eating routine might be too much, even for me.

Although I did do the Calendar Club challenge in April 2020 whilst trying out a vegan diet for all but 2 days of the month… 🤔
I might re-think this if it goes well for a week.

Intermittent fasting is...

described more as an eating pattern than a diet - it doesn’t define what you eat but gives you a window within which to eat. Fasting for the rest of the time is said to have clear benefits for your body, and I also believe your mind.

Some benefits (the ones that I’m interested in, anyway):

  • it can help weight loss, and in particular, belly fat loss
  • when I exercise I’ll be burning fat stores more often, rather than carbs from the food I’ve preloaded with
  • fasting this way reduces the amount of food you consume when you actually do eat, reducing caloric intake
  • short-term fasting can increase your metabolic rate, helping you burn even more calories

My fasting

I chose an 8-hour eating window with 16 hours of fasting. Ideally, 8 of these hours would be asleep, so pending any sleep-walking midnight snacks, I’d be fasting anyway.

Potential problems and solutions

  • Conflicting with work schedule, not having free time to break the fast:
    • Have snacks on hand and time meetings appropriately.
    • Work’s core hours are supposed to be 10:00-12:00 and 14:00-16:00 anyway.
  • Exercise in the morning:
    • Do only a short strength session in the mornings, if anything.
  • Exercise at lunchtime before eating:
    • Do only a short 2-mile run, which is what I do for my standard lunch break route already.

Choosing a window

I wanted to keep it consistent each day so my options for the 8-hour window were:

  • 09:00-17:00 - a good time for breakfast, but early dinner
  • 10:00-18:00 - good for family dinner time
  • 12:00-20:00 - a good length of time in the morning, and good for snacking into the evening after exercise
  • 13:00-21:00 - a late lunch, perhaps too late to be snacking too

I chose 12:00-20:00. The 4-5 hours in the morning between waking up and eating is a good length of time to burn fat, and a good length of time to be disciplined for.

Once you’re through this stint, that’s 5 of your 8 fasting hours dealt with (the other 8, you’re asleep for).

Family dinner time is usually between 17:00-19:00 so that’s catered for in this window too, along with a bit of time to snack if I’ve done some training in the evening.


What I did

I have only black coffee and water in the morning before I break my fast. This helps me control my hunger. It’s extremely important to stay hydrated, and most people who fast tend to consume calorie-free drinks during the fasting stage so I figured black coffee or tea would be okay.

I usually exercise before I eat. At first, this almost killed me, but perhaps that was because I was trying to run sub-7:30 minute miles... When I got used to it, I paced myself better on these runs and actually ended up feeling really good. I didn’t risk having a full stomach or feeling bloated before a run and utilised my fat stores from the previous day’s eating to power me. I felt physically fresh and had a sense of achievement afterwards.

I eat quite a big lunch after the exercise to recover and to drive my afternoon. I have coffee throughout the rest of the workday and a big healthy dinner in the evening before the 20:00 cut-off time.

I go to bed feeling more content, and am more ready to sleep without a belly full of biscuits!


How I felt

  1. Hungry
  2. Fresh - much less groggy
  3. Disciplined
  4. Concerned - about eating enough during the window
  5. Shattered - this was half marathon day
  6. Strong
  7. Tired and craving - I’d been up since 05:00, which increased the number of fasting hours

I’ve felt the physical benefits - more weight and fat loss than I’d usually expect in a week, feeling fresher in the mornings and not so full and bloated before I do my lunchtime exercise. It served to make me feel less groggy in the mornings, too.

Having a week of intermittent fasting has helped my discipline and focus a great deal. I enjoy testing my resolve with experiments like this. It shows me that I can do whatever I put my mind to.

It’s had a small impact on the amount of time I save in the morning and evening with food prep and procrastination - it’s contributed somewhat towards simplifying my daily routine.

I’ve found that I don’t eat snacks between meals anymore - I don’t even think about them with this new routine.



Before the experiment

  • Weight: 11st 6.8lbs
  • BMI: 23.8
  • Body fat: 12.7% (it was a gluttonous Christmas)

After the experiment

  • Weight: 11st 2.4lbs (net loss 4.4lbs)
  • BMI: 23.2 (net loss 0.6)
  • Body fat: 12.2% (net loss 0.5%)

Screenshot of Feelfit app with my weight statistics

FeelFit, with my statistics

Will I continue?

It turns out I probably need to do this for longer to get real benefits. I enjoyed the discipline it gave me and the time in my day I got back from going straight into work without taking time for breakfast and snacks.

It’s not just the physical and social benefits that I’ve gained from trying intermittent fasting, but the mental too. I enjoy testing my resolve to stick with a habit like this and I have that sense of achievement that I’ve been able to.

Now, for a snack.

Thanks for reading! 👋🏻
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