You’ve heard the preachers, including me, talk about how important it is to eat every 2 to 3 hours.  And how important breakfast is.

But are we right?

pic: Does fasting help or hurt fat loss and muscle building?
Does fasting help or hurt fat loss and muscle building?

Two counter-approaches contradict the above recommendations:

a)      Intermittent Fasting (complete fasting for at least 24 hrs once a week or so)

b)      Semi-Fasted Cardio (first thing in the morning after about 12 hours of not eating)

Today we’ll cover the pros and cons of intermittent fasting.  Then next week we’ll cover “semi-fasted cardio”.

Here’s today’s outline:

  • Pros and Cons of Fasting
  • Roots of Fasting
  • Fasting for Fat Loss
  • Fasting for Muscle Gain
  • Making Fasting Easier – 10 Tips

Let’s start with a summary, then follow with the details:

Pros And Cons Of Fasting For Fat Loss And Muscle Gain

Pros For Fasting

  • Possibly very effective for fat loss, as studies show increase fat burn compared to carb burn, during fasting (much more detail on this in the rest of the article!)
  • Easier, for some people, than being in slight caloric deficit each day
  • Most people get a natural “high” on those days; better attention; surprising increase of energy
  • More time for life; less time cooking, eating, and doing dishes
  • Increased natural growth hormone:  potentially good for muscle gains (much more detail on this in the rest of the article!)
  • Disrupts the body’s expectations about food, thus preventing diet plateaus (hypothetical)
  • Confidence – any time you try something difficult, and then turn that into a habit, you will feel more confident in yourself; this will lead to you accomplishing more over the course of your life
  • Bragging rights – most people are impressed with someone who has the discipline to fast one day a week
  • Potentially clears the body of toxins and waste
  • Anecdotal benefits to a whole range of health issues, from reducing arthritis and migraines to improved skin and hair

Cons For Fasting

  • It’s harder, for some people, compared to being in s slight caloric deficit each day
  • When starting out, difficult to judge impact on strength and energy; could lead to injury if not careful
  • Could trigger overeating the following day
  • Increased irritability in some people
  • While you can see hypertrophic gains from lifting in a fasted state, the hypertrophy tends to be sarcoplasmic, not myofibrillar (see J Physiol. 2005 October 1; 568(Pt 1): 283–290.)  While a full explanation of this is beyond the scope of this article, strength gains are associated with neural adaptations and myofibrillar hypertrophy, not sarcoplasmic hypertrophy
  • Could be abused/overdone by impatient people seeking fat loss

Let’s explore the science behind these, especially the impacts on muscle gain and fat loss.

The Roots of Fasting

Fasting in general has been practiced for centuries (maybe even longer), mostly for spiritual or religious reasons.  Many major religions involve fasting or partial fasting for parts of the year.

And in the past few decades, fasting has been popular for health as a “cleansing” effect.  Eliminating intake supposedly gives your body a rest from all that hard work of digesting food and fasting allows your body to eliminate even more waste.

But what about for more specific health benefits, particularly for people like you who are interested in crafting an amazing physique by building muscle while achieving a “leanness”?

Fasting is associated with reduced metabolic clearance rate of natural growth hormone (GH), more production of GH, enhanced lipolytic responsiveness (higher fat burn), and lower glucose concentrations, decreased insulin sensitivity.  GH is essential for muscle growth, so having more seems like a good thing right?  And with more resistance to insulin spikes, that’s good too, right?  And did you notice I mentioned increased fat burn, rather than carb or muscle burn?  [The reports on this are numerous; I can’t list them all but for example see J. Clin. Invest. 81(4): 968-975 (1988); also see J Clin Endocrinol Metab. 1992 Apr;74(4):757-65.]

These all sound like the magic pill you’ve been waiting for, right?

Yet you hear lots of people telling you to avoid fasting.  Who to believe?  Well, of course it’s not a simple answer.  And it starts with your goals.

I’m going to assume that if you are reading this, one of your goals deal with achieving an amazing physique.  For simplicity, let’s assume that an amazing physique and body composition comes from two sub-objectives: fat loss and muscle gain.

There are some fitness programs out there that you can buy that advocate fasting for lifters.  I could even try to sell them to you and make a commission off the sale, but I haven’t used them.  And I never recommend something I haven’t used myself or at least purchased and read thoroughly to ensure I agree with it.

I think all you need to know is contained in this article.  Then get a good lifting routine like my 6x6x6 Routine or FullBodyAttack.  You don’t need a special lifting routine just because you fast one day a week.

Fasting For Fat Loss

I had a tough time finding scientific research into how fasting affects fat loss, aside from the obvious calories-in, calories-out perspective.  Lots of studies on mice and rats!  But humans are different than rodents.

So let’s state the obvious anyway: fat loss is tied to burning more calories than you consume.

Let’s say you are trying to lose a pound of fat a week.  Most nutritionists agree that a pound of body fat has about 3500 calories.  So to shed that pound, you need to burn 3500 more calories that week than you consume.

If you are a weight training man, you might be on a 3500 calorie per day diet.  So skipping a day, by fasting for 24 hrs a week, automatically equals your target caloric deficit for the whole week, right?

Using simple math, yes.  But there are some reasons to believe it’s not a 1-to-1 equation.  (Note, none of this is directly supported by science of fasting, but is instead my interpretation of related facts.)

  • Trying to exercise hard on your fasting day is tough, because you may have less energy; with less intense exercise, you burn fewer calories so even though you ate 3500 fewer calories, you also burned fewer so the total effects of the fasting ends up being less than a 3500 deficit.
  • Some people fast on their “off day” so they weren’t planning to exercise anyway.  But if that “off” day becomes a totally sedentary day, you again could be in the same situation as the preceding point.
  • After fasting, some people actually overeat the next day or two, so they eat back some of those 3500 calories.
  • Fat loss, as opposed to simple weight loss, is trickier than just calories in vs calories out.  It has to do with timing of calories, quality of calories, type of exercise, etc.

Of course, none of these is universally true.  In fact, a study on Ramadan fasting which essentially prohibits eating from morning until sundown every day for several weeks, showed that for at least that group, overall calories were the same but shifted to mostly proteins and fast (less carbs).  See American Journal of Clinical Nutrition, Vol 62, 302-307, 1995.

But doesn’t fasting break the “eat frequent small meals to increase your metabolism” rule?  By skipping meals all day doesn’t that lower my metabolism?

Well, that’s a popular belief but I can’t find any evidence that a single day a week of fasting reduces your metabolism.  Reduction in metabolism (meaning, the amount of calories burned “at rest”) can occur when your body is consistently in a caloric deficit.

So Is It Better To Fast One Day A Week Or Be In A Small Caloric Deficit Every Day?

I wrote previously about why cycling your caloric deficit is much better than being consistently low, if your goal is to build muscle and lose fat concurrently.  See this article.

But it appears that if you had to choose between eating 3500 fewer calories one day a week (i.e. intermittent fasting), or 500 fewer calories every day of the week, then fasting wins out.  The logic:  your metabolism will stay higher and you’ll have more fuel during the week for your muscle gains.

But what about effects on muscle on that fasting day?  Won’t I burn muscle as well as fat that day?

Fasting And Muscle Gain

It was long believed as fact that fasting forces your body to burn a mix of fat and muscle.  In fact, studies have shown that true starvation response involves your own body consuming all your muscle.  Despite the fact that this muscle-consumption only occurs after many continuous days of fasting, people have extrapolated that to assume even a single day of fasting must burn muscle.  But evidence seems to be emerging to debunk that belief.

In fact, there is evidence that fasting one day a week will actually INCREASE muscle gain!

Hormonal Responses to Fasting

Several studies have shown that natural growth hormones are in fact present in higher concentrations due to fasting.  For example, in Diabetes January 2001 vol. 50 no. 1 96-104,results demonstrate that GH is a decisive component of protein conservation during fasting and provide evidence that the underlying mechanism involves a decrease in muscle protein breakdown.

And hot off the presses, European Journal of Applied Physiology, Volume 108, Number 4 , 2010, 1439-6319 shows that the anabolic response to a protein/carb shake after fasted resistance training is greater than after a fed state.  However, it also appears that there was more muscle breakdown during the workout.  In other words, the benefits of the fasting and the detriments of the fasting may cancel each other out.  Another study would be needed.

For non-training individuals, it appears that overall body composition (muscle to fat ratios) remain unchanged even after long periods of intermittent fasting, as in a Ramadan-type fasting.  See American Journal of Clinical Nutrition, Vol 62, 302-307, 1995.

To repeat my earlier statement, it is a myth that short-term fasting (12 or 24 hours) increases overall body protein breakdown – this does not start until 3 days of fasting (see Diabetes January 2001 vol. 50 no. 1 96-104).

Making Fasting Easier

If you decide that fasting is something to try, here are some tips:

  1. Tell someone you know and trust that you are fasting; it’s always good to tell someone anytime you make a major change in any health practice.
  2. Don’t tell everyone you know you are fasting – you’ll get too many contrasting opinions and it will shake your resolve.
  3. Drink a ton of water.  This not only makes it easier, but it is VITAL to your health.  Black coffee or pure tea is fine too.
  4. Avoid situations that will be hard, like don’t meet a friend for lunch and think you will just be able to resist!  Avoid the temptations, don’t rely on pure willpower.
  5. Start by doing your fast on a recovery day – no intense workout.  Over time you can experiment with doing a workout but do not do a heavy lifting day on a fasting day.  Simply too risky in my opinion.
  6. Initially, try fasting for most of the day, once a week.   Then gradually increase the duration until you get to 24 hrs.  In other words, see how you feel.
  7. The last meal before your fast should be mostly proteins and complex carbs.
  8. Eat dinner the night before, then have your fast last until the next day’s dinner.  That’s usually easier for most people than eating breakfast, then fasting until the next day’s breakfast.  Going to bed hungry can be challenging!  But try both.
  9. Get a good night’s sleep the 2 nights before.  Sleep deprivation triggers hunger.
  10. Relax.  Stress triggers hunger (or the illusion of hunger).  Meditate if needed.

Ending With a Warning

Even though there appear to be many positives, DO NOT start a periodic fasting without considering your overall health and consulting your doctor.  Fasting for 24 hrs could have serious side effects for people with certain health conditions, particularly anyone with blood-sugar related issues.

If you are cleared by your doctor, I recommend taking it slowly.  As shown in several studies (including Diabetes March 2003 vol. 52 no. 3 657-662) the response from individual to individual to fasting varies greatly.

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