Can You Use Intermittent Fasting For Muscle Gain?

12 min read

What You’re About To Get Into

  • The general and undeniable benefits of fasting
  • Moving on from health, how good is fasting for muscle?
  • The pros of fasting for bodybuilders
  • The pitfalls of fasting for bodybuilders
  • Setting up part two

Fasting And Muscle

Here we’re going to answer the big question which comes up around fasting, and whether or not you should. Does fasting suit muscle building?

Intermittent fasting, with its many offshoots, is sitting pretty at the top of the diet trends. That was sealed as much when google released its ‘Year In Search of 2019’. Fasting has exploded recently into the limelight, from being another passenger on the conveyor belt of endless fad diets. Nowadays, you’re guaranteed to have at least a couple of friends posting about their second day of water fasting. And yes, you can check out my thoughts on those two-day fasts. The short-end, it’s not for me.

But regardless of my n=1 experience, fasting is worth the hype. It does something that sets it apart from the rest, by dislodging the emotional addiction of food. When going through long spells of time with only a glass of water for company, the stimulus to eat becomes weaker. Sure you’ll go through a few waves where the discomfort feels unbeatable, but that feeling inevitably vanishes without a trace. 

See here for article on why fasting works so well.

This Isn’t About Whether You Should Fast For Health

Through fasting, the brain can start to untangle the wires that drive up hunger the moment there’s a hint of nearby food. Hunger, for the most part, is an emotional trigger. The physical side rarely gets to factor. There is a lot of science to this diet, but the main benefit is also the simplest one. Fasting gives the body much-needed downtime from the constant feeding cycle. 

But with all that said, I have to hold my hands up and admit that there’s not much to say about general fasting that hasn’t already been said. The spike in popularity also means most of these topics have been beat into the ground. So instead of dwelling on all the tricks autophagy and metabolism, we can look at a matchup that’s less traveled.

Intermittent Fasting For Bodybuilding

Bodybuilding, sculpting, toning, whatever you’d like to call it.

Bodybuilders, better known as competitive dieters. And I don’t just mean the few percenters that sacrifice 20 weeks of their life to get on stage for a few minutes. This is for anyone who’s running through the lifestyle, where the end-goal is reaching and maintaining the lean muscular look.

This is the population that might be more cautious about the effects of fasting. The type of people that need to have a tub of cottage cheese before they tuck up for the night. Because otherwise, the muscle’s just going to eat itself overnight. The kind of bro-science that plays on the fears of gymrats in order to sell fluffed up protein shakes. 

Along the same lines is the built-in belief system that you can only digest 30 grams of protein from one meal. So if you eat anything extra, it’s wasted calories that just get flushed out. And so we have people getting up in the middle of the night in order to get their leucine fix. While also adhering to the elaborate ritual of eating every 2 hours on the clock. Just like the cottage cheese solution, the strategy is to prevent muscle breakdown from outstripping muscle synthesis. 

So you can see where fasting would factor into this. The protein-loading schedule is already balancing on a knife-edge. The thought of missing a meal often have people waking up in cold sweat. Outright banning early breakfasts and midnight snacks should put you on a fast-track to Fight Club’s Brad Pitt. Or does it?

It turns out that the body has a few smart ways of getting around the need to eat every few hours. Fasting is much more than the ultimate caloric deficit. As you stray further and further away from your last meal, the insulin effect diminishes and begins to flat line. While insulin, usually the dominant regulatory hormone, relinquishes its hold on the metabolism, other hormones step up to center stage. That’s the change the comprises most of fasting’s benefits for bodybuilders.

The Benefits Of Fasting For Bodybuilding

  • Lowered Insulin leads to better handling of carbs
  • The lack of insulin also causes more fat-adaptation, increasing the mobilisation and burning of body fat
  • This may also a necessary setting for burning stubborn fat
  • The rise of glucagon speeds up fat burning and ketogenesis, the ultimate level of fat-adaptation
  • Time out of MTOR (anabolism) drops inflammation levels, promoting recovery
  • Digestion is also improved, due to rest and a rebalanced microbiota
  • See here for an article explaining the perks of fat-adaptation.

You’ll see here that many of these positive results aren’t exclusive to a fat-loss phase. Want to gain significant muscle, past the usual newbie gains? You’re going to have to nail the recovery stage. Muscle’s not built in the gym, that’s just the part where you destroy it. It’s digestion, absorption, stress management, and sleep that really prime the body to pile on lean mass.

These effects are going to be significantly dampened in a diet that just features constant grazing and overfeeding. Bloating is not normal. That’s a sign that’s you’ve loaded up with more than your body can handle.

And I haven’t brought up the autophagy, anti-anxiety, increased executive function, working memory, all the sides that should appeal to anyone looking to feel better. Fasting is hugely beneficial, undeniably so. But there’s a catch. It’s a switch that you can use whenever you like, and when you get too trigger-happy, things go awry.

Can You Fast For Days Without Losing Muscle?

If you dipped into the research, you’d find that extended fasting causes no muscle loss, with a plethora of studies showing no adverse effects from going several days without food. In fact, in some cases subjects managed two weeks without losing lean mass. 

But there’s an issue here. Fasting science is mainly borrowed from studies taken with obese subjects. That makes sense, as they have the most to gain, like extending their life by a few decades. But the fact is that this population is a world away from the guys who miss a gym day once every six months. Even when the studies run a strength programme alongside the diet, it’s just not the same. The truth is that the more fat you’re carrying, the less chance you have of losing lean mass. Significantly less. It’s crazy to suggest that you could fast for days without tapping into muscle protein at some point.

There are several reasons why fasting won’t be the optimal way for gaining and preserving muscle mass.

The Dangers Of Fasting For Bodybuilding

  • Fasting inevitably uses muscle stores for fuel
  • Leaner individuals will be at considerably greater risk
  • Fasting can overstimulate the catabolic AMPK pathway
  • MTOR is less stimulated
  • Insulin is reduced
  • Protein synthesis isn’t spread out
  • Protein loss in lean dieters

Looking at the metabolism, the leaner you are, the less your fuel reserves. Fasting will initially tap into glycogen stores, then a mix of fat and protein stores. Not necessarily protein from the muscle, but there will be a net protein loss. There are protective mechanisms that take place during a fast, but it’s a completely different ballgame when you’re down to unhealthy levels of body-fat.

A study following these lines, and bear in mind this was done with rats, showed that the obese rodents were able to fast without showing much of a decrease in MPS. The lean rats, however, ended up with suppression.

Overstimulating The AMPK Pathway

The AMPK can be summed up as the catabolic pathway, which isn’t to say it’s a negative mechanism. Training is AMPK-driven, as is fat loss. It’s the state of famine that balances out the feasting. And since bodybuilders are so dedicated to spiking the opposite pathway, the anabolic MTOR, it’s a necessary means for staying healthy.

But just like MTOR can be overstimulated, so can AMPK. If someone is hellbent on removing the last layer of fat around their abs, then they’ll often go straight for the kitchen sink approach to weight loss. That could be fasting, HIIT, high volume lifting, low calories, low carbs, all rolled into one supercharged stress ball. At this point, you’re not just throwing the AMPK switch. You’re taping it down and strapping in for the cortisol ride.

Fasting has been shown to cause parasympathetic withdrawal, lowering HRV and causing excessive amounts of cortisol. As a translation, it’s too much stress for the body o handle. Which inevitably causes downstream effects of insomnia and strength loss.

More Fasting Means Less MTOR and Insulin

On the other end of the spectrum, there’s the MTOR switch that is now getting neglected. Here’s the basic overview. You have a meal, and the carbs and protein spike insulin. That insulin secretion turns on MTOR, which allows protein synthesis to go up, along with a bunch of other effects.

This MTOR has been propelled in the medical community as the enemy of mankind, and it’s completely unfair. It’s portrayed as an overstimulated mechanism that promotes obesity and shortens lifespans. But once again, that’s skewed towards the research of obese subjects. People eat too much, and far too often, and MTOR ends up getting thrown under the bus. We’re dealing with a drastically different section of the population. 

Bodybuilders need MTOR just as much as they need AMPK. MTOR, along with insulin, is anti-catabolic. It protects the muscle, raises MPS (Muscle Protein Synthesis), and is pretty critical when the objective is to hold onto some size. With fasting, there’s less of an opportunity to turn on MTOR, and this is an even greater case with low carb dieters. 

Ketogenic programmes naturally have drastically lowered insulin spikes, and the body has to resort to using leucine to turn on MTOR and MPS. This works perfectly fine, but the fact is that leucine won’t create as strong of an effect on MTOR. Insulin is usually going to be 3-4 times greater.

Can You Really Get Enough Protein During Fasting?

The old science of having no more than 30 grams of protein per meal, has been displaced as a myth by now. That being said, we’re back to the discussion of whether fasting is optimal. If you were to have one meal a day (OMAD, check my guide here), then you’ll be stuffing anywhere between 100-200 grams of protein in one meal. That’s in a different stratosphere to 30 grams.

So what does the science say now about protein intake? Well, it’s still inconclusive. The recommendations are between 0.4g/kg – 0.55g/kg of protein per meal. You’d end up having to spread out over 3-4 meals in order to hit your quota. There is a hypothesis that extra protein can be stored in the gut for later use. But in order to play it safe, which we’re all keen on when it comes to keeping hard-earned muscle, then you’d be best off with at least two well-sized meals.

Wrapping Up

Fasting isn’t the optimal route for muscle gain, and it needs to be managed for fat loss. This statement should get thrown out if you’re just looking for weight loss, rather than targetted fat loss. There’s going to be a big difference here between a functioning programme and the optimal version.

Fasting doesn’t stop you from getting results, and there are plenty of ways for the body to work around these downsides. If you thrive on a fasting routine, then there’s nothing stopping you from continuing down that road. There are really no downsides at that point. Fasting is generally going to be channeled into a force solely for good.

On the other hand, if you’re striving for the best possible results, then there might be better ways of going about this. In case you want to stuff the science and get the action items, that’s what I’ll be offering in the next article. Over Part 2, I’ll offer strategies that allow you to use fasting during both phases. Whether you’re on a MTOR-fuelled bulking programme, or an AMPK-directed shred, there’s no need to rule out fasting. There are still a lot of benefits relating to insulin sensitivity and fat-adaptation that make it worth the inconvenience of learning the ropes.

How Fast And Still Build Muscle – Part Two