I’ve been doing rare fasts of about 16-20 hours every once and a while for about a year.  In February while on vacation, I decided to make it more of a formal experiment on myself.  This was somewhat of a decision of convenience, as it was just easier to go surf in the morning and eat my first meal of the day around 11.  Ali had to do it too – at least for a week!

Why? —  I don’t know, why not?  I like to experiment mostly. There are some very solid reasons to do this and then some theoretical ones.  Really,  I just wanted to see what would happen with my body.
So what did this look like on a daily basis?
Wake up in the morning – drink coffee, water and tea and no food.  I started eating around 11 or 12 to begin with and after a few weeks I more typically ate my first meal of the day between 1 or 2 PM. I tried to not be too strict with times, but kept it pretty steady. Basically, no food for about 16 hours and eat for about 8 hours.
I ate mostly a plant, meat and fat diet although I’m not shy about eating small amounts of dairy or grains when I feel like I want some (about 80/20 in paleo talk).  Very rare processed food and zero fast food.  I did this most days of the week, but I didn’t do it if it made me feel bad or if I just really felt like eating.  Average of 5 days a week for the last five months.  I checked my DEXA scan before and after.
Results:
1. Basically stable weight.  Lost 2 pounds of body weight.  I lost a total of 4 pounds of body fat and gained 2 pounds of lean muscle mass.  My training regimen did not change in the 4 months I changed my eating pattern.
2.  Lipid panel.  I’m gonna check and I’ll let you know later if you care, but honestly I don’t care too much.
3.  Energy levels.  Most days – great!  I actually find that I’m more productive and have higher energy until I break my fast.  I still have a bit of a hard time breaking my fast.  I’m a BIG eater, so I tend to get a little crazy with my food when I break my fast.  When I do this, it can make me feel a bit sluggish and sleepy.  When I do a better job at breaking my fast gradually I feel just fine.
4.  Performance.  Athletically I mean!!  I’m not gonna talk about the rest.  No change basically.  I have not tracked this statistically, but in general I haven’ t seen either an increase or decrease in metabolic conditioning or endurance.  My lifting has much more to do with how my back feels than my eating, so I don’t have any data in that regard.
Any drawbacks?  Sure.  A few.
1. Fasting is a bit of a stimulant.  I am much more sensitive to caffeine when I fast.  I had a few days where I over did it with the coffee and got jittery.  I am even more sensitive to alcohol while fasting.  This is not a good way to break a fast.  Your tolerance goes way down.  Cheap date for sure.  Also along this line, if had something stressful in the morning (speaking conferences, tense conference calls) I noticed that I didn’t tolerate fasting well on those days.  I just plan on eating early breakfast when I have those situations.  I really don’t like public speaking and its probably one of the biggest stressors I face!
2.  People think you are weird.  Even weirder than they already do.  Some might even think you have developed an eating disorder.  Well –  F ’em.  I don’t really care and you probably shouldn’t either.  They are also having a hard time catching their breath while making fun of me as we walk up one flight of stairs together!
3.  There are days where events get in the way of your plan.  This was not really a big issue.  I just went ahead and ate if I felt like it.
4.  Long work outs.  Like long meaning 40-60 minutes of continuous WOD (think Murph) or hard lifting for over 70-80 minutes.  These are tough in a fasted state.
My personal experience with this mirrors larger data sets, but with every thing diet, it all depends on your own experiment.  I think this does help to dispel a couple of common myths about fasting.
1.  You will loose muscle.  This is not supported by any data or my experience.  It has been extensively supported by your jacked and tan bro at the shake shack that wants to sell you some killer new supplements and a banana chocolate peanut butter smoothie. Bro – don’t miss the window of  gainzzzz!
The basis for this myth comes from experiments performed on single cells not animals on a macro level and certainly not humans.  It is true that your body uses stored protein during fasting but it not in the way you think. This happens during autophagy.  This is your body’s natural process of using waste material inside of cells as fuel in the in between stages of fasting as its moving towards using your body fat as fuel. A lot of these waste products are indeed proteins, but this is NOT synonymous with degradation of muscle cells themselves.  Autophagy is a very important process of eliminating cellular waste, but there is NO evidence that this process decreases muscle mass on a larger scale.
2.  You will be sluggish.  This was definitely not the case for me.  It is likely that this will happen to you if you eat a refined high carbohydrate diet.  It is similar to a common dip that many will experience after transitioning from refined diets to natural foods.  When you diet you are essentially eating your stored meals – yes that is what my love handles are – just a few extra meals!  If your body is not prepared to use fat for fuel you will probably have a hard time fasting and will feel sluggish.
So, back to the first question.  Why do this?  What happens when we fast?
The answers are not that complicated, but they often don’t compute well because it flies in the face of conventional nutritional wisdom.  As you probably already know, I believe that “conventional nutritional wisdom” is an oxymoron of the highest order.  If a nutritionist or doctor gives you nutritional advice, your best bet is to do the exact opposite.  Remember that I don’t count.  I’m a neuroradiologist – just a geek in a dark room reading MRI’s – not a real doctor.  So don’t ask me about your damn rash or that lump on your scrotum please!!
The first thing to realize is that fasting has NOTHING to do with calorie restriction.  The human measurement of calories don’t really mean a damn thing to your body.  It is a measurement of potential energy held within chemical bonds in different compounds that gets released during combustion. Your body does not combust foods! Your body doesn’t count calories and it doesn’t communicate in units of calories. It does however speak fluently in the language of hormones.  That is how your body controls energy use and storage.  One more time to be clear – fasting has nothing to do with calorie intake. It has everything to do with hormones.
When you fast (which by the way you get away with doing every single night without somehow wasting your biceps into little raisins) your insulin levels drop.  They drop very low.  Insulin is the master hormone which lets your body know when to store energy or when to use it.  You can visualize it as the gatekeeper for use of fat as fuel.  When it is high, your body will not use fat as fuel – either the fat on your thighs or the fat you ate in your last pint of Phish food ice cream.  When insulin levels are low your body will begin using fat as fuel.  Very simple but profound concept.  You can keep insulin levels pretty low by eating a natural food diet, but fasting will get them even lower.
So when you stop eating during sleep every night insulin levels drop and you start metabolizing your own personal energy fat stores as energy. Simultaneously your body begins scavenging degraded proteins and free radical damaged compounds in your cells to recycle as additional building blocks for energy.  Your body preferentially spares intact proteins in lean muscle by the secretion of HGH and testosterone.  Yes, the exact same substances that folks go to the doctor and pay hundreds of dollars a month to get injected into their bodies. Your body makes this stuff all on its own!! This process is well on its way by the time you wake up and then you –  – HAVE to eat the MOST important meal of the day (pretty sure Kellogg sponsored that slogan).
This process comes to a screeching halt after your first bite of cereal.  It comes to less of a screeching halt if you eat real food, but it doesn’t’ stop at all if you don’t eat. Actually very well conducted studies have shown that HGH levels continue to rise during a fast up to about 20 hours – between 1200 -2000% increase.  Although I haven’t seen studies on testosterone, it is very likely that they track together to a large degree.  This is what keeps your lean muscle intact and may actually be a stimulus for muscle growth.  There is of course a break point.  Fasting for very long periods of time (more than a couple of days) will eventually begin to drop your HGH and testosterone levels.
Once you take your first bites of food this hormone cascade is reversed and your body begins the process of energy storage.  This is the normal ebb and flow of energy in our bodies.  The real problem is that the balance is usually WAY off.  There is consistent ebb and no flow.  For most westerners, the body does not spend enough time in the utilization phase and a whole bunch of time in the storage phase of hormone balance.  Hence – excess body fat.
Take aways:
1.  Fasting is normal.  This is part of everyday life that has been eliminated to a large degree by the abundance of food, abundance of toxic food like substances (think Taco Bell) and bad nutritional advice.  It is not strange, dangerous or bad for your health.  Your body probably needs some rest from the constant onslaught of food, at least on some level.
2.  Usually it a positive experience rather than a negative one.  Sometimes it sucks- so then eat and the suck goes away.
3.  Always challenge nutritional dogma.  Be a skeptic.  Even of me. Or especially of me.  Try things out and see what happens.  My only caveat to this is you actually have to try it – not half ass it.  This takes time, dedication and patience. My personal experience is that diet related stuff takes 3-4 months for a reasonable trial period.
4.  It probably doesn’t matter all that much if you cook and eat natural foods and are happy with your level of body fat.
Who should do it:
1. Experimenters. Why not.  You can always go back to eating sour patch kids during your workout if you don’t like it.  (thats right – I’m on to you!!  I hear all.). I’m pretty sure this is how the Rock got those huge pecs.  Maybe I’ll try that next.
2.  You’ve got your diet dialed in but are looking for more rapid or pronounced fat loss.  Let me repeat – this is NOT for you if have a crappy diet.  It will frustrate you and not work well.
3.  Those looking to optimize anabolic hormones (HGH/testosterone).  Intermittent fasting is a perfect protocol for both males and females looking to get higher levels of these hormones. This is a double whammy in relationship to body fat.  Excess body fat is highly estrogenic.  This means that any circulating testosterone that you may have will be largely converted to estrogen by any excess fat cells.  As you get rid of more body fat, less of your circulating testosterone will get hijacked into the production of man boobs if you are a guy and for stimulating breast cancer cells if you are a lady.  Also for the ladies, don’t worry about testosterone.  Females just don’t have the adequate hardware to produce large amounts of testosterone.  You will not experience the dual scourges of male pattern baldness and clitoromegaly that plagued the eastern european weight lifting teams of the 1980’s. This requires injectable steroids – a la Ivan Drago of Rocky IV fame.
4.  You have a hard time with breakfast.  This is a common problem I hear with people trying to transfer to eating real food.  People just can’t get away from the habit of eating candy for breakfast in the form of boxed cereals or granola.  Go ahead and skip it then.  Have a cup of coffee and be on your way.  You will be just fine.
Who should not:
1. You are pregnant or lactating.
2.  You are happy with your level of body fat and hormone levels. You are right where you want to be from a nutritional and health standpoint.
3.  You still eat a mostly refined food diet or very high carbohydrate diet.
4.  You don’t give a shit.
Let Ali know if you have any questions!
Jer