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Stick with this fitness thing long enough and you'll notice that everything gets recycled. Exercise and diet trends come and go... then come back around again later. It's a lot like fashion.
One dietary approach that's found a resurgence in the last few years is intermittent fasting and all of its variations. And since there are so many variations, we'll refer to it as time-restricted feeding (TRF), which literally means that you eat only during specific hours of a day.
Virtually every culture in existence has historically used some form of voluntary food restriction, mainly for healing or spiritual purposes. But to my knowledge, those cultures never used fasting as an approach to getting jacked. Those bros didn't even wear fanny packs, so clearly they had no idea about what it took to get swole.
So TRF isn't new, but the internet is bursting with lean dudes showing us how it got them knuckle-skin lean and how it's superior to every other type of fat loss approach. Are they right? Should your fat ass do some form of meal skipping? It's possible. Let's take a look at the benefits first.
When it comes to turning on muscle growth, mTOR is what activates gains. It's the pathway that drives cellular growth in the body and regulates protein synthesis. mTOR responds to big eating by letting the body know that sustenance (mainly protein) is in abundance and that it's time to party. But ideally, you'd want to turn on mTOR selectively, then turn it back off. Which leads us to one of the greatest benefits of fasting: autophagy.
This word literally means "self eating," but it's actually not a bad thing. Think of it as the body's self-cleaning process, or natural form of true detoxification. Autophagy is cool. Your body is smart enough to use the leftover and damaged protein "parts" to create newly functional proteins.
During autophagy your cells create membranes that seek out damaged, dead, or unusable cells and use them for energy to create new cells. It's activated by AMP-activated protein kinase (AMPK) when nutrient intake is insufficient for an extended period of time (fasting).
So let's address the elephant in the room: The people opposed to fasting use autophagy as an argument that TRF "causes your body to eat through muscle tissue," also known as catabolism.
Their claim is that an absence of protein intake is what causes this, and that protein turnover is constantly happening in the body, so without constant consumption of it, we just waste away. This is rubbish. In the context of this type of diet, autophagy is the process where the body recycles damaged cells.
AMPK also does a pretty nice job of reducing low-grade chronic inflammation. This is important because just about every major disease known to man has some sort of relationship with chronic inflammation.
AMPK helps to combat inflammation by reducing the nuclear factor NF-κB signaling system, which is a pro-inflammatory signaling pathway. (Nuclear factor signaling system is also the most awesome band name waiting to happen ever.)
Fasting also increases the production of the ketone body beta-hydroxybutyrate, which inhibits the NLRP3 inflammsome. The combination of these bad boys doesn't just reduce chronic low-grade inflammation, it improves immune system function, and creates a more robust and healthy physiological environment.
The cascading effect here also includes insulin. We can't ignore the connection between low-grade inflammation and insulin resistance. Not only will reducing chronic inflammation reduce your chance of an early grave, it should also improve your insulin sensitivity. And that means better nutrient partitioning, which means a harder, leaner body.
The 16:8 protocol is when you fast for 16 hours and eat meals within an 8 hour period. It's so simple that most people can do it fairly consistently. And if you do it with some guidelines, it'll keep muscle retention high and help you take advantage of insulin sensitivity, when it matters most, through nutrient timing.
To maximize fasting benefits – for muscle retention and fat loss – do this:
Let me emphasize that nutrient timing when going into training fasted or semi-fasted (you break your fast about 15 minutes prior to training here), becomes more important than training in a fed state, where you've eaten 90-120 minutes prior to training. In a fed state, getting in a good meal an hour or two after training works just fine. If you choose to train in the manner above, I highly recommend this protocol because the selected nutrients are ones that get through the digestive tract rapidly and into the cells very quickly.
Sometimes it's best not to subscribe to ANY diet until you've got your mind right. If you're putting your health in harm's way just to eat less, then that's a problem, and adopting another diet strategy won't fix it.
If you've struggled with overeating or binge eating, beware. Going without food for longer spans of time may simply increase your appetite for more food during the eating window than what you'd consume with a regular (not time-restricted) diet.
Another reason TRF is not ideal for binge eaters is because it can create a false sense of accomplishment. You might think you're eating less overall simply because you're eating within fewer hours of the day. But anyone can out-eat their maintenance level of calories for the day in about 12 minutes. Using a form of TRF could cause someone to binge during the eating window.
It's not a magic bullet for fat loss, nor is it a killer of gains. Fans of it might get caught up in thinking it's the former, while the opposition will say it's the latter.
Any type of time restrictive eating does not expedite fat loss any faster than a diet where calories are controlled for each day. Remember, 3000 calories in a day is still 3,000 calories in a day regardless of the time frame you eat them. Fat loss occurs when you've been in an energy deficit consistently for weeks at a time.
And just like eating more meals more frequently doesn't "speed up the metabolism," eating fewer meals less frequently won't slow it down, or increase fat oxidation unless there's an energy deficit achieved at the end of the day.
There's a ton of information related to TRF and the benefits of it. It's well beyond the scope of a single article. What's important to remember is that any type of TRF is really just a tool in your dietary toolbox. Understanding the benefits of it and how to apply them for your goals is key. If it helps you reach them, who can argue with that?
But if you don't like intermittent fasting, don't do it. Being lean and eating whenever the heck you want is also a win. And compliance matters most. So if you can't adhere to a dietary approach, then all the science in the world means nothing.
