Intermittent Fasting
Tatiana Keay, RD, CPT
Everyone may be quick to
jump in to give their opinion on this topic. I was one of them when I overheard
someone in my philosophy class raging about "intermittent fasting".
To start off, I have to reveal that there are three different types of intermittent
fasting.
1.alternate day fasting
2.whole-day fasting
3.time-restricted feeding
For the sake of this post, I'll only be going over the current fad.
When you read “intermittent fasting” throughout this post, I am regarding the
time-restricted feeding type of fasting. In time-restricted feeding, 16-18 hours
of the day are spent fasting or not eating. The other 6-8 hours are an open
window for meal times.
So what is this intermittent fasting fad all about? It’s not
really a diet because you are not restricting any foods. A “routine” is a
better description of intermittent fasting.
A certain number of hours are
designated as the fasting window and the remaining hours are the feeding window.
You may ask, “So I eat all my calories in 6 hours!?” Yes, precisely.
Who the
heck started this?
Martin Berhan a nutrition consultant and personal trainer
popularized this diet. Martin's system is called the Leangains Method. Notice the feeding time is from noon-8pm allowing an 8 hour eating window. Of course, many people intermittently fasting are not following this EXACT regimen, but it is an example of what a day/week would look like.
Consider This...
Claims:
- Decrease body fat percentage
- Maintain/increase muscle mass
- Longevity by decreasing risk of heart disease and cancer
Also, many “nutrition consultants” consider intermittent
fasting NOT a diet, but a pattern of eating. It’s not about WHAT you eat but
WHEN you eat.
Some
Bio physiology
Between 18 and 24 hours of fasting, the following happen:
- 50%
increase in fat oxidation
- 50%
decrease in glucose oxidation
- Declines
in plasma insulin may contribute to the increase in lipolysis
In simpler terms, our body burns fat for fuel
instead of carbohydrates.
So the claim for decreased body fat is supported.
What about my muscle?
So we know that our body is burning fat for fuel but what about
protein? This is a concern for many of us. We have worked hard for our muscle, and can't afford to lose any of it! Research studies did find that there is an increase in amino acid release, but
the majority of these studies made comparisons between an overnight fast and a
period ≥60 hours later.
Intermittent fasting does not last for 60+ hours, only 18 at most. So the likelihood that you would lose all your muscle while intermittently fasting is low.
The most interesting study I found was an 8 week experiment on
male athletes conduced in 2016. There were 2 groups: one group practiced time-restricted feeding (TRF) and the other was on a regular diet.
Researchers
found that TRF group had
1. A greater decrease in fat mass
2. Muscle mass remained
the same between both groups
3. Lab values remained the same except testosterone
and insulin-like growth factor 1 which decreased significantly in TRF group.
Dietitian Recommendations
Intermittent fasting is NOT for everyone. Including me! I am a snacker and I like to eat throughout the day. Someone like my husband really enjoys this eating routine and has seen tremendous results.
If you do choose to try intermittent fasting, get medical supervision
(RD, MD). Having a professional making sure you are getting all your nutrients within that 6-8 hour window can benefit.
More research needed specifically
for
time-restricted feeding type of intermittent fasting.
What do you think? Would you be able to follow this eating routine? Comment below!
References
Grant M. Tinsley, Paul M. La
Bounty; Effects of intermittent fasting on body composition and clinical health
markers in humans, Nutrition Reviews, Volume 73, Issue 10, 1
October 2015, Pages 661–674, https://doi.org/10.1093/nutrit/nuv041
Clear, James; The Beginners Guide
to Intermittent Fasting; http://jamesclear.com/the-beginners-guide-to-intermittent-fasting
Chaix, A., Zarrinpar, A., Miu, P.,
& Panda, S. (2014). Time-restricted feeding is a preventative and
therapeutic intervention against diverse nutritional challenges. Cell
Metabolism, 20(6), 991–1005.
http://doi.org/10.1016/j.cmet.2014.11.001
Moro, T., et al. (2016).
"Effects of eight weeks of time-restricted feeding (16/8) on basal
metabolism, maximal strength, body composition, inflammation, and
cardiovascular risk factors in resistance-trained males." J Transl Med
14(1): 290.
