"You can only burn fat if you keep stoking your metabolic fire and eat 6 times per day!"
"If you don't eat breakfast you'll get fat!"
"Fasting will cause you to get hit by a bus and pirates to kill your family!"
When it comes to breakfast, meal timings and the like, there's a hell of a lot of misinformation out there. And it's so easy to buy into it, as so much of it seems like it makes sense on the surface. Add a sprinkling of broscience to back up the claim, and you're hooked.
So let's clear some things up, and look at why Intermittent Fasting is so celebrated currently. I've broken this up into a few smaller posts as opposed to one monster, as there's a lot of material connected to it.
"You'll lose muscle if you don't eat every two or three hours!"
No you won't. The human body has had to deal with scarcity for the majority of it's existence. Yes, our bodies are slowly adapting to modern day abundance, but they're not "there" yet. Often, this myth is supported by the claim that "the body can only absorb 30g of protein at a time". Just think, if that was true, our ancestors would have been screwed. And it would mean overeating wouldn't be an issue, because hey, you can only process a certain amount of it!
Whilst it is true, that over the course of around 3 hours, the body will absorb only 30g of protein, this does not mean that it suddenly throws in the towel, stops absorbing it, and starts eating itself.
In one study, the sample meal was still being digested, and nutrients absorbed, well over 5 hours after ingestion. This sample meal? A cheesy pizza. Simple carbs, readily digestable dairy proteins, all in all a very easy to digest food. With foods requiring more time to digest, such as a nice big cut of meat with a heap of vegetables, it could be way over 10 hours before your body is "done". And even then, it won't turn to eating muscle.
The 30g figure most likely stems from a 1997 Study by Boirie et al., which quantified the absorption rates of different types of protein. It discovered that, in a fasted state, 30g of whey protein (one of the fastest proteins to digest) took between 3 and 4 hours to be entirely absorbed. However reading further into the study than just a skim read, one discovers that even other dairy proteins such as casein were still being absorbed over 7 hours after ingestion. It is speculated that most whole food proteins have an absorption rate of between 3 and 6g per hour. So as long as you're getting your protein from high quality sources, you're probably fine.
So that's the protein absorption taken care of. Now for the muscle loss.
Only in really prolonged fasting can catabolism start to rear it's head, when stored liver glycogen is depleted. To maintain blood sugar, glucose is created from amino acids. This is not a sudden switch, it's a gradual process, and yes, if amino acids are not available from food, these amino acids come from the body, i.e muscle. One study found that amino acids account for about half of glucose level maintenance after 16 hours of fasting, and pretty much entirely after 28 hours, when the glycogen stored in the liver is fully depleted.
Assuming however, that you don't start fasting for ridiculous periods, and that you have a high protein meal before commencing the fast, there is no threat to your precious muscles.
Martin Berkhan, of Leangains.com, whose resources I am heavily leaning on to write this (thanks Martin!), says the following of the matter:
"Whenever you hear something really crazy you need to ask yourself if it makes sense from an evolutionary perspective. It's a great way to quickly determine if something may be valid or if it's more likely a steaming pile of horseshit".
That's generally pretty good advice for a lot of this diet stuff.
Coming soon: Stoking the metabolic fire.
This post intends to encourage a more critical approach to nutrition, and hopefully spark an interest in the science behind it. It is not a peer reviewed journal article. Our understanding of the body is developing constantly, and this post was written with the materials currently available at time of writing. Should you find there to be any glaring mistakes, I would appreciate an email to chat about them!