Intermittent Fasting

I recently commented on a thread, within the bodybuilding.com forums. that dealt with the topic of intermittent fasting (IF). Subsequently, I was contacted by the originator of that thread and asked to further elaborate on some of the points I was making and further delineate some of the articles/studies I was referencing. This post is the result of that request.

Although there is no clear definition about what actually constitutes IF, most agree that it entails periodic denial of calories for a 24-48 hour period. It's not just skipping a meal here and there.  From a bodybuilding /sports performance perspective the question for IF is, can it be an effective tool achieving and maintaining optimal body composition while at the same time allowing or facilitating maximum performance.

Based on current research, I believe that IF has great potential value for the general population. Animal studies, in particular, show both an overall improvement in several physiological and cognitive markers and actually show increase in lifespan similar to what has been seen in restricted calorie studies, Human clinical trials likewise show great improvements in insulin sensitivity, blood triglyceride levels, reduction of bodyweight and actual improvement in the hormonal cycles related to hunger and satiation. What's more, most subjects of these tests report that the ability to "sick with" an IF protocol is actually easier than trying to restrict calories on an every day basis, even though weekly and monthly calories totals end up being the same.

All this shows great promise and may be one of the strategies that could be employed in overcoming our national obesity epidemic.

At the same time, one must recognize that most studies are conducted on overweight individuals, not hard training athletes.  This poses a problem for the bodybuilder or endurance athlete wanting to minimize body fat while simultaneously maintaining an extremely intense exercise regimen in that findings may not be applicable to their circumstances.. 

Of note and value, though, there is at least one athlete oriented clinical study that I ran across.  Presented in the Clinical Journal of Sports Medicine, it looked at the performance effect of Ramadan (daytime fasting) on several 5000 meter runners. In this case, over a month long period of day time fasting, the runners lost strength as measured by maximal power output and actual race performance decreased by 5%.  The number of participants and the specifics of the testing points to the need for more studies and is inconclusive for bodybuilding purposes.

Some protocols, described on various bodybuilding Web sites, describe various IF-like feeding protocols that curtail calories during set times during a 24 hour period, usually allowing/recommending feedings around the anabolic/recovery  nutrient window pre and post exercise.  The most popular is referenced as 16/8, meaning you take in no calories for 16 hours (this includes the time you're sleeping) and then you consume your allotted calories just prior to and for the next several hours after your daily workout.  This is very similar to what is described as the "Warrior Diet," described in a book of the same name. Anecdotally, this seems to be a very effective methodology for many practitioners and may be worth a try.

As most know, I am an extreme pragmatist.  If something works for you, no matter the clinical/scientific evidence or the experience of others, keep doing it,  If IF works for you, keep doing it.  If you want to give IF a try, go ahead, it might give you the mental or physical edge you need and I have seen no evidence that it is truly harmful.

At the same time, I will continue to employ the frequent feeding methodology and recommend it to most of my clients.  It does take discipline to master, but has produced proven results in both sports performance and optimizing leanness..