7 day water fast

Nothing but water

I recently completed a fast in which I consumed nothing but water for seven days.

The notion of a water-only fast was non existent in my list of priorities until I came across a few episodes on the Smart Drug Smarts podcast. There are several episodes that feature various medical doctors and professors that specialise in the area of fasting and the study of subsequent health effects/benefits on humans. I can be a pretty lazy person in honesty, so I thought.. Not having to worry about any food preparation for seven days? Sure.

Key pointers of complete caloric restriction and my experiences:

  • Reducing the intake of carbohydrates to less than 20-50g per day will put the body in to a state of ketosis. This is where your body starts burning stored body fat instead of glucose (carbs). This is a perfectly normal biological function.

  • Starves out cancer. Research indicates a 7-day water fast once per year could be a good preventative measure for cancer by increasing mitochondrial respiration and killing off weak/unstable cells and replacing them with new, strong and healthy ones.
  • Immune, metabolic and biological benefits
  • Complete caloric restriction (as opposed to ketosis via a diet) is said to give the body extra legroom to repair and regenerate within the body as it doesn’t need to focus as much energy on digestion during the fast
  • Surprisingly, daily bowel movements
  • Important to note that I was already half keto adapted going into this fast. My body is used to using keytones for energy and I didn’t have that painful three day break in period those who have never been ketosis would get.
  • I didn’t leave the house much unless it was for work or walks. I wanted to preserve energy and also was paranoid something might happen if I was ‘out’.
  • Steady water intake of 2-3L per day
  • My concentration seemed limited while fasting. I couldn’t sit down for hours like I normally can. I had to get up and vary my actions or everything became frustrating, boring and intolerable.
  • Dizziness was apparent through most of the fast, but mostly during times of sudden rapid movement, not continuously.
  • When leaving the comfort of my house, everything seemed easier to manage and to put up with. It’s like being at home put a lot of emphasis on the fast and this kept my mind on it 24-7. Being at work made me forget about much of the experience, and helped pass time by focusing on other things.
  • Falling asleep and having a constant, undisturbed rest was harder than normal. This is apparently common among those who have fasted before.
  • Fasting myths – At the bottom of the page is a link to a fantastic blog post by Dr. Jason Fung on the many myths and misconceptions about caloric fasting. These are things like starvation mode, muscle loss, being ‘just bad’ for you etc. Very worthwhile read if you have five minutes.

Day 1 & 2

Very easy. No distress here. Quite productive on day two (which is usually what running on keytones will do for you). Lost 2.2kg.

Day 3

Spent 6 hours feeling a bit under the weather which could be a toxin flush. Also overslept which certainly didn’t help with that awful groggy feeling. I closed my eyes for 10 minutes and it instantly disappeared. I felt perfect for the rest of the day. My journal notes describe it as a bogged down feeling, almost like a slight hangover. First spout of dizziness felt on this day. Mostly watched movies to pass time. Lost 1 kg.

Day 4

Felt pretty great today. Got through some health documentaries that I had been hearing about. “That Sugary Documentary” was one of them. Interesting watch. Little bursts of dizziness when making sudden movements. Lost 2kg.

Day 5

Experienced quite a lot of intense arm and leg aches. Felt like I was going through growing pains again. It made work extremely uncomfortable and almost unbearable. Surprisingly, I still had my ability to mentally focus and concentrate on my tasks though. Lost 0kg.

Day 6

I mostly felt tired. Dizziness remained consistent with previous days. Was pretty mentally over it by this point. My colleagues will attest about how much junk food I was talking about that I most certainly couldn’t eat. Lost 1kg.

Day 7

Ended the fast about half way into the day. Technically I should have waited until I woke up the next day, but my work here was done. Especially since I was already keto adapted going into the fast to begin with. I had lost a substantial amount of weight and felt it too. I’m sure my body did a significant amount of repairing and cleansing during the 6.5/7 days of not eating. Prior to starting, I didn’t eat right up until I fell asleep either. So I could probably argue it was the right amount of hours in total.


Very happy with a 6.2kg loss. Several days after finishing, I’ve only put about 1kg back on, but this is expected because there is food inside me now! I started off with a light salad with some healthy fats. This gave me a little boost. It wasn’t until the following day that I felt completely ‘normal’ again though. The next sleep after eating food, I slept for about 9 hours uninterrupted and I woke up feeling amazing. I would love to know why I lost no weight on day 5. I mean, from a biological point of view, how is this possible? If I have had zero calorie intake, and my body has spent 24 hours chewing through fat/keytones to keep me alive and functioning, how can there be no loss? Would love to find out more.

For those who are curious, there was no physical ‘hunger pains’ for the duration of the fast. It was all psychological. My brain knew I was unable to eat, and therefore kept telling me “oh wouldn’t it be nice to go and get xyz food right now”. Interesting experience.

Resources & notes:

  • Ketosis vs Cancer – Smart Drug Smarts with Thomas N. Seyfried Ph.D.
  • Starvation And Its Benefits – Smart Drug Smarts with Valter Longo, Ph.D.
  • /r/keto
  • Fasting myths – Jason Fung MD
  • There are probably tons of other credible sources of information by doctors and professors sharing fasting/ketogenic knowledge. I haven’t looked for them all and this list is certainly not exhaustive.
Written on January 16, 2016