We do not have to eat all the time, therefore we are free to choose when we eat.
– Brad Pilon
Fasting, once seemingly reserved for a niche subset of the bodybuilding community, is quickly gaining popularity, not only among bodybuilding and fitness enthusiasts, but also among public health and longevity researchers.
What is Intermittent Fasting?
The concept behind fasting is simple. Don’t eat. It’s not actually so radical a concept. The classic “three meals a day” eating style is really a product of the last 150 or so years (depending on who you ask). Before then, eating habits varied widely between cultures and time periods in terms of the standard number and timing of daily meals. In fact, for most of human history, going hungry for days at a time was likely the norm.
Fasting proponents, from bodybuilders to longevity researchers, have discovered that longer-than-standard periods of not-eating can have dramatic physiological benefits.
Fasting and Body Composition
For obvious and not-so-obvious reasons, fasting can be good for body composition (more muscle, less fat). The obvious reasons:
- When you spent less time eating, you may eat less overall
(meal size may not increase to 100% cover calories in “removed” meals)
- When you spend less time eating, the things you eat may change
(less dessert if you don’t eat after 8!)
However, research shows that even holding calorie consumption constant, fasting strategies can result in improved body composition (both reduced body fat and increased muscle). Magic. Sorta. More to come on that.
Fasting and Health/Longevity
This is where the research gets really interesting. Sparing the technical details, fasting seems to be a type of hormetic stress. That means stress that causes a response in the body leaving it better prepared for stress in the future. Just like strength training is a stressor that ultimately improves strength, fasting is a stressor that causes a host of positive adaptations in the body.
To list a few outcomes observed in animal and human models, various types of fasting protocols have been shown to result in:
- decreased fat mass
- increased lean muscle mass
- improved glucose tolerance & blood glucose levels
- improved lipid profile
- reduced inflammation and c-reactive protein (CPR, an inflammatory biomarker)
- higher mitochondrial volume (cellular energy factories)
- protection from mild age-related fatty liver
- generally favorable improvements in gene expression
- increased production of ketone bodies
- decreased breast cancer risk and reduction in recurrence
- improved effectiveness of weight-loss therapy
- improved sleep
From a bio-mechanism standpoint, it is currently thought that fasting promotes two processes, programmed cell death (apoptosis) and cell disassembly/clearing (autophagy), which sound scary but just result in the destruction and clearing of damaged, aged, or otherwise compromised cells (which is really awesome).
On the flip side, during the re-feeding period post-fast, stem cells are stimulated to create brand new, healthy, “young” cells. Basically, we’re talking about stimulating the body’s build-in anti-aging mechanisms at the cellular level. The research here has tons of promise for longevity and health-span. Super cool.
There’s still a lot of research to be done to understand both the mechanisms for these benefits and other benefits that may be associated with fasting, but so far the results are looking extremely promising.
“Don’t eat sometimes” is fairly nebulous advice. Perhaps not surprisingly, many different strategies can be employed to varying effects. I haven’t personally tried most of the methods, and the research is still fairly nascent in terms of comparing them, so take all of this with a grain of salt. In general, there’s no consensus on naming scheme for different method, so bear that in mind as well
Time Restricted Feeding
Perhaps the most well-known method – a general strategy of a largely fasted day with one restricted window each day for eating. These strategies are the most commonly seen recommended for body-composition goals, but research shows health benefits beyond just body comp as well. Common feeding windows include:
- 10-12 hours (in Dr. Satchin Panda‘s and Dr. Ruth Patterson’s research)
- 8 hours (in Martin Berkhan’s “Leangains” method)
- 4 hours (in Ori Hofmekler’s “Warrior Diet” method)
Occasional 24-hour fasts. Common protocols include:
- The “Eat Stop Eat” Method popularized by Brad Pilon – one or two 24-hour fasts each week
- Alternate-Day Fasting – eat every other day
As you’d expect, this is the most “extreme” of the bunch – although not terribly out of the ordinary in our evolutionary past. Largely isolated to research and medically-supervised situations for the time being, but potentially the most advantageous for longevity-promoting effects. Dr. Valter Longo is the pioneering researcher in this area that I’m aware of.
As I described briefly in my “journey” post, I have personally found success from a body composition perspective with a daily 8-hour feeding window (roughly the Leangains or Renegade Diet method). Most of the time that has meant two meals (lunch and dinner) and a snack or two. I believe that to be a good starting point for most people, although a 10-hour window would be fine and give a little more flexibility.
I’ll be sharing more specific experiences and recommendations in future posts, but hopefully this is enough to whet your appetite.
Other resources to check out for more information:
- [Podcast] Dr. Rhonda Patrick on The Tim Ferris Show
- [Website] Found My Fitness (Dr. Patrick’s site – see also her podcast and YouTube channel)
- [Blog] Leangains
- [Blog] Eat.Blog.Eat
- [App/Study] MyCircadianClock (participate in Dr. Panda’s research through a mobile app! science!)
- [Book] The Warrior Diet
Thoughts? Fears? Other responses? Comment below.