Intermittent Fasting –A Passing Fad Or Useful For Athletes?

This is how I felt when I first heard of intermittent fasting.

I have learnt in the past, a lot of things come in and out in the fitness community but only a few actually work.

This is why I like the basics – stick to them- get good at them.

No crackers, Gromit! We've forgotten the crackers!

The main benefit I could see from IF is the CONVENIENCE.

Eating 8 meals a day is a hassle for anyone.

Last year my life had become extremely busy and cluttered. I didn’t have time to familiarise myself with the basics of fasting before I jumped right in. After initial the initial adaption period (I felt horrible adjusting to it), it wasn’t that bad.

I started to lose fat, especially in those awkward areas – around the hips and chest. But after few months I became smaller, much smaller, my friends said that I look sick and eventually my lifts started to plummet.

So I ditched that and started reading around. I came across a book by Brad Pilon Eat.Stop.Eat [76].

To lose fat – short term fasting and exercise is an easy way to create a caloric deficit. We can cope with periods without eating- as starvation doesn’t mean not eating for a few hours [76].

Reducing calories (or fasting for short periods) doesn’t slow the metabolism and it doesn’t cause a muscle loss. Muscle tends to not waste away especially when we are training heavy (heavy lifting is essential when dieting).

Brad gives various examples of studies where metabolism and caloric intake was measured. One in particular showed that fasting for 3 days (72hours with no food) didn’t slow your metabolism down [76].

Kind of makes you rethink meal frequency and the eat every 2 hours idea.

The Role of Glucagon, Insulin and Hormone Sensitive Lipase:

During fasting our muscles start to switch over and start oxidising fatty acids for fuel. Insulin (a fed state hormone) causes storage of calories from food into glycogen and fat [76].  Glucagon is an important hormone in the early fasted state as it stimulates lipase, inhibits pyruvate kinase, and affects enzymes which favour gluconeogenesis.

Lipolysis is controlled by hormone sensitive lipase which hydrolyses triacylglycerol’s. Triacylglycerol’s are hydrolysed by lipase to the free fatty acids and glycerol. In white adipose tissue it lacks the enzyme glycerol kinase so glycerol can’t be metabolised. In the absence of insulin, the fatty acids are released from the adipocytes for use as a respiratory fuel by the liver.

Catecholamine’s have a potent stimulating effect on lipolysis while insulin is a strong inhibitor, where the plasma concentration of both is dictated by blood glucose concentration [37, 78]. Furthermore adaptation to prolonged starvation, cortisol stimulates the synthesis of hormone sensitive lipase.

John Berardi has published a great Free E-book on Intermittent Fasting.

There were a few people noticing the same problem with intermittent fasting (eventual muscle loss) so I started doing my homework.   

I stumbled upon Kiefers work. His idea is: the main reason fasting works is due to the absence of carbohydrates and not just food.He mentions how IF lacks long term studies.

  • High insulin tailors for lipogenesis and low insulin for lipolysis. Metabolism crashes after prolonged caloric and carbohydrate restriction (Part 1).
  • Within 12 hours of fasting, several regulators of growth shutdown the mTOR pathway – a very important pathway for protein synthesis and breakdown prevention. John Meadows has an article on mTOR and maximising protein synthesis.

mTOR pathway inhibition prevents resistance training from triggering muscle growth, insulin mediated muscle breakdown prevention, decreases free IGF-1 and allows cortisol to breakdown muscle tissue (Part 2). It makes me want to weep after reading that.

  • Fasting for more than 12hours will inhibit the mTOR pathway and allow macroautophagy to destroy muscle (Part 3). So is fasting useless?

Long term fasting might be good for fat loss for people who aren’t interested in muscle gain and performance. The key is to fast long enough to trigger macroautophagy without down regulating the mTOR pathway (Part 3).

Keifer continues to produce some great work on the benefits of skipping breakfast. We wake up every morning ready to burn fat, due to hormonal fluctuations over the 24 hours period. This fat burning effect gets dampened when eating carbohydrates – as insulin increases – ghrelin and GH are inhibited. So  skipping breakfast and the overnight sleep is how he uses fasting.

Cortisol which rises during the night accelerates fat burning in the morning. Ghrelin is released during the night and stimulates GH release, causing the release of more fat to be burned and lowering protein use as fuel.

If you’re fasting overnight eat some fat and protein when you wake up. You will get the fasting benefits without muscle breakdown. The idea is to under eat before training and then feast after. So the day is splint into no carbs before training and carbs after. This provides materials for growth and prevents catabolism doing too much unvented damage.

He also has a great article on the effects of meal frequency on metabolism and weight loss. Bigger or smaller meals don’t speed up or slow down metabolism -the number of meals doesn’t matter for fat loss – only calories do.

This article took a while to research and write – share it if you found it useful :)

[expand title=”References used (Click here to expand)“]

37. A.E. Jeukendrup, W.H.M Saris, A. J. M Wagenmakers (1998). Fat metabolism during exercise: A review, Part2.  Int. J. Sport. Med. 19, 293-302.

76. Eat. Stop. Eat Book by Brad Pilon.

78. The Ultimate Diet 2.0 Book by Lyle McDonald.


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