Disclaimer: I am not a doctor nor a scientist, simply an interested layman who spent a little time reading online and watching documentaries. I do not advocate water fasting. This post is simply an account of my own experience and opinions and is not intended as medical or fitness advice.
The Handsome Hubby and I finished our second longer-term water fast just less than two days ago. For the most part, the low-carb/keto/IF community understands fasting and is aware of what most of the benefits are, but I’ve gotten a few horrified questions and run up against a few people who were certain we were going to starve. And I understand. I had the same fears about fasting until the Handsome Hubby started looking closely into it.
As I mentioned previously, I’m wary of appearing to advocate or recommend fasting, but it occurred to me that it might be beneficial to my readers if I share some of the benefits of fasting and the science behind those, as well as share my experience. All I can do here is skim the surface as there’s a great deal of research out there, some of it Nobel Prize-winning. If you find the subject of interest, don’t stop with this post. Hit up Google!
There are two sets of goals in fasting. The first is the more obvious, weight loss and reduction of body fat. The other is more subtle, the things that take place on a cellular level that renew some of the body’s systems, help in fighting disease, and may (or may not) extend life.
Longer term fasts, like the ones I’ve done recently, serve both purposes, but people usually embark on them for weight and fat loss purposes. Most people believe fasting will “eat up your muscles”, but the opposite actually happens. Once you’ve burned through any glycogen stores (which takes no time if you’re already following a ketogenic diet but can take a couple of days if you follow a standard high carb diet), your body enters a ketogenic state, in which it makes ketone bodies from your fat to burn as fuel, sparing your lean muscle mass. This is most probably a mechanism that evolved early in human development, to keep the unfed body strong and energetic enough to keep hunting and gathering to find that next meal and keep the individual, and the species, alive. The best explanation I’ve encountered so far of how the research into this phenomenon developed is contained in the second half of a documentary called “The Science of Fasting” (2012), which can be found online. You can also check out this talk with Dr. Walter Longo, one the most prominent figures in this line of research.
In my own experience, on my first fast, after re-feeding, I ultimately lost only about 3 pounds, but my body fat percentage dropped by 4 percentage points, from about 26% to about 22%.
The Handsome Hubby and I completed that first fast and the one we just finished primary to take advantage of this fat loss effect. In future, we plan to do shorter 5-day fasts a few times a year, solely for the cellular benefits.
Research has shown that, in just three days of fasting, the body can rejuvenate the entire immune system, primarily by killing off damaged white blood cells, which are then replaced by fresh new cells within 48 hours of re-feeding. The article I linked also touches on how the body can help repair cellular aging, reduce tumor growth, and help protect against the harmful effects of chemotherapy.
Autophagy, or autolysis, the process by which cells repair and rejuvenate themselves, is also promoted by fasting. This effect strengthens and regenerates the very substance of the body on a microscopic level, and might theoretically result in longer life, and greater health throughout that life.
As for my as yet very limited personal experience with fasting, one result I didn’t expect was to learn so much about myself. Many people rest during fasts, but the Hubby and I don’t. I still lift weights and we still hike together almost daily. We’ve always carried snacks with us on hikes, and on any outing that might last over two hours, because I get shaky and feel weak when I don’t eat fairly regularly. For that reason alone, fasting was unappealing to me, and we thought I might not do well with it. I was stunned to discover that, not only could I fairly effortlessly fall into the habit of NOT eating, but even when I get shaky and feel weak during a fast, I have much greater strength than I would ever suspect. I can keep hiking and push up inclined trails even when my brain tells me I don’t have the energy. This revelation alone was worth the experience to me.
Speaking of energy, many people report boundless energy and mental clarity while fasting. I have not experienced these lovely side effects, though I wish I had. At workout time each day, once I started lifting my strength was sufficient (although we both noticed a substantial drop in stamina and endurance), but trying to encourage myself to get up and do it was a bit of a challenge throughout our fasts. I also felt somewhat disconnected and fuzzy-brained, which made writing new blog posts rather a challenge as well!
On our first fast, I did 6 days fasting, took a break for 4 days while the Hubby was still fasting, then finished up the last 7 days with him. On this most recent fast, we did 14 straight days together, and I learned something else important. About 11 or 12 days is my limit. I made it to 14 days, but those last couple were very tough.
As it turns out, the lack of energy I experience while fasting, and difficulty I experienced during the later days, is due to my comparatively low body fat stores, according to Dr. Jason Fung in the obesity code podcast, wherein he states, “The amount of energy we have to use when fasting is based upon how much body fat we have, which gives up its energy at a fixed rate according to A limit on the energy transfer rate from the human fat store in hypophagia. If you have 10 pounds of body fat, then you can generate 315 kCal per day, which would be a state of significant caloric restriction. If you have 60 pounds of body fat, you can generate 1,890 kCal per day, and now we’re talking about a pretty adequate amount of energy to fuel your day.” So there it is. More body fat equals more of that elusive boundless energy!
For those of you who’ve asked, I don’t have final data on my body composition results from this last fast. I know I lost approximately 12 pounds, but that isn’t a final figure. When you fast, some of the weight you lose is simply the emptying of your digestive system, while you’re adding nothing back into it. When you do eat again, the food you eat has weight and takes time to traverse your digestive system, so most people gain three or four pounds just from that effect over the first few days. I’ll be weighing and measuring myself and taking progress photos on Sunday for Monday’s Update post, so all of those figures will be included there.
And please, if you’ve ever had an eating disorder or are prone to binging, please do not ever try fasting unless instructed to do so by your physician. Fasting is not a reasonable or safe long term weight management plan, and it can easily contribute to disordered eating. Be healthy, know your limits, and take care of yourselves!