Intermittent Fasting, according to a comprehensive survey of my fellow dietitians, is expected to be the most popular nutrition trend of this year.
Yes, even more popular than keto.
Given how frequently my clients broach the subject with me, I’m not surprised by my colleague’s assertions in this regard.
In today’s piece, in light of latest book on fatty liver disease, explores the evidence around intermittent fasting and NAFLD (non alcoholic fatty liver disease).
With the shameless book plug out of the way, let’s get to the good stuff.
Fasting, Fatty Liver & The Mitochondria
A great deal of intermittent fasting research to date, particularly in animal models, has looked at the potential benefits of fasting on the health and functioning of the mitochondria – a component of cells responsible for energy metabolism.
The effect of lifestyle strategies on mitochondrial health has been a topic of great interest in the scientific community because the mitochondria are increasing thought to play an important role in longevity and chronic disease prevention.
Before we go any further it is important to note that the vast majority of studies on intermittent fasting and the mitochondria have been conducted in animals, so we cannot make definitive claims about this interaction in humans just yet.
So where does the liver come in?
If you’ve been following my recent blog content on fatty liver disease you will know that scientists strongly believe that the improper functioning of the mitochondria has a big role to play in the development of NAFLD.
This theory relates to the fact that the mitochondria are responsible for fatty acid metabolism and that NAFLD is partially a disease of improper fat metabolism because fat ends up where it shouldn’t – on the liver.
I’ve explored the connection between fatty liver disease and the mitochondria in two previous blog posts looking separately at L-Carnitine and Saturated Fat.
- L-Carnitine is a naturally occurring compound which carries fatty acids to the mitochondria to be metabolized. When provided as a supplement to those with fatty liver disease, there is some evidence that liver health improves – providing credence to the relationship between the mitochondria and liver health.
- Saturated Fat is found largely in high fat red meat and dairy products and may increase liver fat accumulation in those with fatty liver disease. Initial evidence suggests that this effect is brought about, in part, because saturated fat may interfere in mitochondrial functioning specifically for those living with NAFLD.
With all of that out of the way, let’s get to the good stuff.
Intermittent Fasting & Fatty Liver – Human Studies
As of right now the current excitement around intermittent fasting has not yet been matched by the appropriate quantity and quality of human studies examining its effects, although that reality is rapidly changing as public and scientific curiosity around this concept increases.
A 2021 systematic review and meta-analysis out of Frontiers In Nutrition found that intermittent fasting could reduce liver enzyme levels (ALT,AST) in people living with fatty liver disease.
The majority of studies in this particular meta-analysis were based on participants engaging in Ramadan fasting which pretty closely replicates the prototypical 16:8 fasting regimen where by a daily fast of around ~16 hours is observed.
In another 2021 systematic review and meta-analysis, this time out of Diabetes Research and Clinical Practice, the relationship between Ramadan structure fasting and decreases in liver enzyme levels (AST, GGT,ALP) was confirmed.
The researchers described the effect of fasting on these enzyme levels to be small but statistically significant.
Finally, in a 2019 randomized controlled trial out of Scientific Reports researchers found that alternate day fasting ( 18:6 fasts, every other day, eating 70% of usual intake on fasting days) not only reduced liver enzyme levels but also improved some indicators of liver fat accumulation and scarring.
In all of the studies discussed above, it’s hard to say with certainty that the outcomes achieve by these fasting protocols were independent of the weight loss that the participants experienced.
It has been suggested, but not yet proven, that intermittent fasting improves liver health independent of weight loss/caloric restriction because it changes the way the body utilizes energy and favours the metabolism of fat – thus theoretically acting to improve the body’s ability to breakdown excess stored liver fat that is characteristic of NAFLD.
This is theoretical of course and remains to be definitively demonstrated and replicated in high quality human studies.
So Should You Try IF For Better Liver Health?
Great question, I’m so glad I asked.
The reality is that I’ve done an incredible amount of research and writing on how one can improve NAFLD through lifestyle modification.
There are quite a few things you have to consider first if you want to fight back against NAFLD including physical activity, dietary optimization and strategic supplementation.
Intermittent fasting, for some, could be the icing on the cake to all of these strategies for which better and higher quality evidence exists of a strong positive effect on liver health.
Most of the evidence suggest that a more modest 16:8 style fast, at most, is potentially sufficient to contribute to reduced liver enzyme levels.
How relevant these reductions are in the grand scheme of things, and compared to all the other things you could do to improve your liver health, is much harder to say.
The good news? I can help you strategize for all of the above – so don’t hesitate to reach out.
Oh! And I happen to have a book on the subject too, and it’s on sale now so be sure to check that out too.
Until next time
Andy De Santis RD MPH