24-hour fasting experiment

What is fasting?

In simple words, fasting = not eating. There are several of protocols used as therapeutic fasting or fasting-mimicking diets (e.g. intermittent fasting, alternate day fasting, calorie/protein restriction).

Why fast?

There have been many experiments conducted in all sorts of critters (from yeast to humans) to study the impacts of fasting. Results from both non-human and human studies suggest that fasting could extend lifespan, reduce oxidative stress and inflammation, prevent neurodegenerative disease, improve cognition, reduce cancer growth and enhance metabolic function, among other health benefits. The mechanisms behind those effects include the production of ketones and their role as an energy source for the brain, the reduction of blood glucose and insulin, and the stimulation of apoptosis (programmed cell death) and autophagy (cellular cleanup process).

The aim of this post is not to cover all aspects of fasting therapies, but to report on my n=1 experiment. If you’re interested in learning more about fasting/fasting-mimicking diets, here are some resources:

On to the experiment

I have been thinking about doing this experiment for a few years but life always got in the way. The opportunity presented itself when my husband had to travel for a job interview (I find it easier to experiment with my diet when he’s not around).

My last meal was Sunday lunch. I had had neck and shoulder pain for a few weeks, so I went for a massage, then came back home, watched a documentary and did some work. I drank several cups of warm water and didn’t feel hungry until 20:30ish. I did a short meditation, prepared my stuff for the next day and went to bed around 21:30. I was expecting having trouble falling asleep due to:

  • Not having done any physical activity
  • Being slightly hungry
  • Having trouble sleeping when my neck hurts
  • My personal heater (i.e. husband) being away

I was awake until 3:00. My alarm buzzed at 6:00, so I had a grand total of 3 hours of sleep. I tried to go back to sleep but couldn’t, so I decided to get up and go on with my day.

I got to work half hour earlier than usual. By then I could recognise the signs of full ketosis: a clear brain and low body temperature. Hunger came and went but didn’t last long. I contemplated having my morning coffee as per usual (after all, it has negligible energy and zero protein) but decided to stick to water.

The hardest part, surprisingly, was not flicking through Instagram food photos, but smelling my coworkers’ lunches around noon. I normally eat at noon but this time I had to wait until 13:00 to complete the 24 hours. I’d say the last hour was probably the hardest, also because I finished the work I was doing so had nothing pressing to keep me distracted. I ate my lunch plus a few handfuls of macadamias sprinkled with sea salt not because I was hungry, but to make sure I was making up for some of the calories that were not consumed during the experiment. I kept drinking water throughout the day.

That night I did a Krav Maga class as per usual, and surprisingly didn’t feel any shortage of energy nor strength, despite having slept only 3 hours and eaten just one meal within the previous ~30 hours. The lack of sleep didn’t hit me at all, but I’m not sure if I can attribute this to fasting.

Parting thoughts

From what I’ve read, I think there is compelling evidence to suggest fasting once in a while is beneficial. It makes sense that lack of energy intake would elicit a hormetic response and allow cellular cleaning processes to occur. It also makes sense from an evolutionary perspective that we should not have food in our bodies 24/7.

My plan is to implement fasting periods of varying durations whenever there is an opportunity (e.g. travel, periods off training such as dealing with injuries, etc.).

Ketosis and athletic performance

The Sydney Morning Herald published an article on this topic last week (you can find it here). In it they describe how endurance athlete Tim Reed adopted a mostly ketogenic diet and the impact it has had on his performance. They also present work by professors Tim Noakes and Grant Schofield who are very well-known in the low carb high fat community.

Anyway, the article is pretty decent, except that they show a picture of a breakfast entitled “full fat: slow burn food?”. The plate contains potato chips, half a roasted tomato, 3 strips of roasted capsicum, baked beans, a sausage and a slice of toast topped with a fried egg. It looks very carb-loaded to me! I ran a search in MyFitnessPal.com and lo and behold, here’s the rough composition of the meal:

Food Portion size Fat Carbs Protein
Fast foods – Potato, french fried in vegetable oil (Generic) 1 small 16.0 34.0 4.0
Beans – Baked, canned, plain or vegetarian (Generic) 1/2 cup 0.0 27.0 6.0
Sausage – Beef, fresh, cooked (Generic) 50 g 14.0 0.0 9.0
Roasted Roma Tomatoes (Eurest) 1/4 cup 1.0 2.0 0.0
Pepper Red Roasted (Parkhurst) 1 Oz 0.0 1.5 0.0
Bread – White, toasted 1 slice 1.0 12.0 2.0
Eggs – Fried (whole egg) (Generic) 1 large 7.0 0.4 6.3
Total 39.0 76.9 27.6

Moral of the story: if you feel inspired by Tim Reed’s story give ketosis a shot but don’t think a breakfast like that will take you there.

If you want to learn more about ketosis and athletic performance check out Ben Greenfield and Dr Peter Attia‘s work.