Have you ever wondered if intermittent fasting was good for bulking? After all, it helps you produce more growth hormone, which purportedly helps with muscle growth; it increases increase in insulin sensitivity, which could help make your gains leaner; and research shows that it helps preserve muscle when losing weight. This could theoretically make intermittent fasting a good bulking diet… right?
On the other hand, most bodybuilders bulked up by doing the exact opposite of intermittent fasting. The guys with the most famous physiques in history all ate at least a few meals per day. Why?
Furthermore, we skinny guys are notorious for having tiny stomachs, raging metabolisms and small appetites—all of which make bulking up way harder. Will intermittent fasting work for our skinny “ectomorph” body type?
There are good arguments to be made for and against intermittent fasting. In this article, we’ll go over the muscle-building advantages and disadvantages of intermittent fasting, then take a look at some studies that compared it against a traditional bulking diet. By the end, you’ll be able to decide if it’s a good approach for you while bulking.
- The Benefits of Intermittent Fasting While Bulking
- Does Intermittent Fasting Prevent Fat Gain While Bulking?
- The Benefits of Eating More Frequently While Bulking
- Intermittent Fasting vs Traditional Bulking
- The Best Types of Intermittent Fasting for Bulking
The Benefits of Intermittent Fasting While Bulking
First of all, intermittent fasting does have some proven benefits. For example, here are four high-quality studies showing an increase in growth hormone in men while intermittent fasting: study, study, study, study.
It’s now mainstream scientific knowledge that intermittent fasting has several proven benefits that can improve your health and body composition:
- Reduction in appetite leading to a comfortable decrease in total calorie intake.
- Increased production of human growth hormone.
- Improved insulin sensitivity.
- Less risk of muscle loss compared to a standard diet.
- Greater cell repair (autophagy).
These claims aren’t being disputed whatsoever in the scientific community. Here’s Examine.com giving a mainstream definition and summary of the research on intermittent fasting:
Our bodies are well equipped for long periods of time without food. Generally, a bout of feeding and digestion is followed by an episode of digestive quiescence (i.e., fasting). In modern days, feeding is rather frequent and fasting tends to be limited to our sleep, plus one or two hours on either end. In other words, no more than 8–12 hours for most people. Intermittent fasting (IF) simply extends this fasting period.
Fasting can be defined as voluntarily abstaining from food (or from certain types of foods) for a given period of time. IF can take many forms, such as alternate-day fasting (ADF), 5/2 dieting (eating at most 500 kcal on two non- consecutive days each week), and time-restricted feeding (TRF; eating only within a set daily time window, which usually lasts 8–12 hours). Ramadan fasting (the Muslim holy month, during which food and drink are consumed only when the sun has set) is a religious form of TRF.
Compared to eating normally, TRF reduces fat mass without affecting fat-free mass or strength from a concurrent resistance training program. Compared to daily caloric restriction, ADF produces greater reductions in fat mass and smaller reductions in fat-free mass. In addition to its proven efficiency, IF has the advantage of only restricting when you eat, not necessarily how, meaning that it can be integrated with other dietary approaches that you enjoy.
However, as you can see, most of these benefits are being researched for how they affect fat loss, not muscle gain. What we’re interested in is how intermittent fasting affects bulking—weight gain.
Because we’re only interested in bulking, we can immediately discount the main advantage of intermittent fasting: appetite reduction. After all, we aren’t trying to eat less food. Quite the opposite, actually. This is a bulking disadvantage, especially for naturally skinny guys, as most of us already struggle to eat enough to gain weight. (If you’re struggling to gain weight, here’s our article about how to eat more calories and gain weight more easily.)
But let’s ignore that disadvantage for a moment. Just for the sake of argument, let’s say that even while intermittent fasting, you’re able to eat enough calories to gain weight. If you can eat enough calories, then you can make leaner gains, right?
Does Intermittent Fasting Prevent Fat Gain While Bulking?
Intermittent fasting is an extreme example of calorie cycling. To understand how intermittent fasting affects our gains, first, we need to understand how regular calorie cycling affects our gains.
How Calorie Cycling Affects Bulking
The first thing we need to do is make a distinction between bulking and cutting. You can use calorie cycling to help with either goal, but the effects are rather different. When you’re bulking, you’re in a calorie surplus, and your body is totally primed for muscle growth, allowing you to build muscle quite rapidly. Mike Israetel, PhD, summarizes the benefits of a calorie surplus as follows:
- More testosterone and insulin
- Enhanced cellular signalling
- Massive nutrient influx
So while we’re bulking, we have quite a bit of potential to build muscle. Let’s imagine it with a simplified graph like this, where the empty area under the dotted line is how much muscle your body is capable of building over time if you do everything perfectly:
As you can see, it’s not a flat line. Your body will be primed for muscle growth after a good workout, and then that muscle growth will gradually slow down as time passes, usually grinding to a halt within 48 hours.
The other thing to keep in mind is that any calories which cannot be invested in muscle growth will be stored as fat. This means that if you eat a large calorie surplus (blue line), you’re going to gain a maximal amount of muscle (red) but you’re also going to gain quite a lot of fat (yellow). This called a “dreamer bulk,” and it looks like this:
Most people don’t want to gain that much fat, so they do what’s called a “lean bulk,” where they eat a smaller calorie surplus, like so:
By bringing down your calorie intake, you’re still gaining almost as much muscle, but you’ve slightly reduced the amount of fat that you’re gaining. However, this is a compromise. You’re not eating enough calories to fully maximize muscle growth after your workouts, and you’re also gaining some extra fat because you’re not tapering off your calorie intake as your muscle growth potential slows.
You can improve your gains by lining up your calorie intake with your muscle growth potential, eating extra calories in the couple meals following a workout, and then easing back on the calorie surplus afterwards. This is still a “lean bulk,” but now with the help of calorie cycling, we’re getting a little more muscle growth:
The first thing to note here is that even though you’re calorie cycling, you’re still always in a calorie surplus. The degree of the surplus varies, but that blue line representing your calorie intake is still always above the baseline (the black line at the bottom). There’s a constant influx of nutrients, your body is always pumping out tons of testosterone, and you’re always benefitting from enhanced cellular signalling. This ensures that you’re building muscle all day long, taking full advantage of your growth potential. (This is how we structure the diet in our Bony to Beastly Bulking Program.)
The next thing to note is that even though your calorie intake follows the curve of your muscle-building potential, there’s still that thin yellow strip of fat gain. You could try to get rid of that yellow strip by reducing your overall calorie intake… but you probably shouldn’t. In order to get all of the muscle-building advantages that come along with a calorie surplus, it actually helps to have a little bit of padding there. Bulking isn’t about eating enough calories, bulking is about eating extra calories.
Now, this doesn’t mean that you should be getting noticeably fatter as you bulk. If you start bulking at 15% body fat, then so long as you’re gaining 85% muscle and 15% fat, your body fat percentage is going to remain at 15% as you continue gaining weight. Furthermore, because your muscles are growing so much bigger, you may even look leaner as grow. (We have a guide about body-fat percentage here.)
That would be the ideal situation, anyway. Realistically, you’re probably going to gain a few body-fat percentage points. Maybe you anticipate this, so you start your bulk at 11% and then stop bulking when you notice that your body fat percentage has climbed to around 15%. For example, here’s Jared gaining 33 pounds in 90 days, with his body-fat percentage rising a little bit as he bulks:
Intermittent Fasting is Extreme Calorie Cycling
Intermittent fasting doubles down on calorie cycling. During the feeding windows, you have more than enough calories to build muscle at full speed, and during fasting periods, you’ll actually dip into a calorie deficit, losing fat. This creates the misconception that you can lose fat even while you’re bulking up.
The misconception comes from the fact that in order to gain weight you need to be in an overall calorie surplus, and that means that during your feeding periods, you need to make up for all the calories you missed while fasting. This means eating so many damn calories that there’s no way to invest all of them into muscle growth, causing the extra calories to spill over into fat storage. So what happens is that you lose a bit of fat while fasting, then gain a bunch of fat during the feeding window, like so:
How to Make Leaner Gains with Intermittent Fasting
If you’re bulking very slowly, gaining just a pound or two each month, then your calorie surplus doesn’t need to be very high. In this case, with such a small overall surplus, you miss out on the extra testosterone, nutrients, and cellular signalling, so your growth potential slows down, like so:
You won’t be able to build muscle as quickly, but you may still prefer this approach. For example, if you’re a fitness model trying to maintain yearlong leanness, and you’re happy making very slow gains, you might prefer this method.
Guys like Martin Berkhan (LeanGains) and Gregory O’Gallagher (Kinobody) do a good job of this. They might be able to get results that look something like this:
However, to say that their programs are designed for this would be to sell them short. Even the LeanGains intermittent fasting protocol is designed for fat loss and muscle maintenance, not for bulking. To quote the guy who created it, Martin Berkhan:
The “gain” in Leangains can therefore be a bit misleading, as most of my clients wants to lose fat, while retaining as much muscle as possible in the process.Martin Berkhan, creator of LeanGains
Using Intermittent Fasting for Cutting
I don’t want to make it seem like I’m thrashing intermittent fasting. The evidence is quite clear that intermittent fasting is fantastic when you’re trying to lose weight. It allows you to dig into a massive calorie deficit for most of the day, and then you can pop up for a bit of muscle growth in that prime post-workout window, like so:
Yes, the amount of muscle you build will be small compared to when you’re bulking, but with traditional cutting, you wouldn’t be building much muscle anyway:
Again, I should point out the exceptions. Total beginners, obese people, and guys on steroids can build muscle and lose fat at the same time more easily, so they can expect better results than are shown in these graphs. This applies to all of the graphs equally, whether or not they are calorie cycling or intermittent fasting. On that note…
Calorie Cycling Isn’t Very Powerful
Calorie cycling pales in comparison to the quality of your workouts, the quality of your diet, your overall calorie intake, your overall protein intake, and how well you’re sleeping. Because the effects of calorie cycling are so minor, I would consider it a bonus technique, not a foundational technique. However, it does work, and because it’s so easy to add into your routine, we recommend it to almost everybody—including all of our members, both when cutting and bulking.
Does Intermittent Fasting Allow for Leaner Bulking?
So does intermittent fasting allow you to make leaner gains while bulking? No. If you’re trying to build muscle quickly, you’ll likely make leaner gains with regular calorie cycling instead of intermittent fasting. However, it won’t impact your gains that much either way (study), and the difference may not even be noticeable, so you should also factor in your personal preferences.
Okay, now that we’ve seen what intermittent fasting can and cannot do, let’s see what frequent eating has to offer.
The Benefits of Eating More Frequently While Bulking
There used to be rumours about “stoking the metabolic fire,” where in order to maintain a healthy metabolism, people thought they had to eat every three hours. That was disproven, and it was more of a fat-loss concern anyway.
When it came to bulking, bodybuilders worried that if they spent a prolonged period of time fasting, then their bodies would begin to eat away at their muscle mass (catabolism). That was also disproven. Intermittent fasting is fantastic for maintaining muscle mass, even in an overall calorie deficit.
However, research has turned up some genuine advantages to eating frequently:
- If you eat twice as often, your meals can be half the size. This allows guys with small stomachs to comfortably eat enough food while bulking, and it prevents the feelings of lethargy after large meals. One good way to take this principle even further is by having snacks between meals.
- More testosterone. Being in a calorie surplus allows you to build more muscle by improving testosterone production, cellular signalling and providing a constant influx of nutrients. The more time you spend in this muscle-building surplus, the more muscle you will build over the course of the day.
- Less cortisol? A recent study looking at 16:8 (LeanGains) intermittent fasting found that the group who skipped breakfast not only produced less testosterone, but also more cortisol—even while eating a comparable amount of calories overall. This would lead to less muscle growth and more fat gain. However, some of these hormonal changes, while not good for building muscle, might be good for improving your longterm health. So it would seem that intermittent fasting would perhaps be better for day-to-day muscle maintenance, but worse in terms of trying to build muscle leanly.
- More muscle-protein synthesis. Researchers have proven that every time you eat a meal that’s rich in protein, you trigger muscle growth (aka muscle-protein synthesis). This means that the more often you eat (up to a maximum of 5 meals per day), the more muscle growth you can stimulate.
Let’s dive deeper on that fourth point. If we’re intermittent fasting, are we sabotaging our gains by missing out on opportunities to trigger bonus muscle growth?
Stimulating Muscle Protein Synthesis
Dr Layne Norton’s research is the most relevant here (study, study, study). We’ve already shown how lifting weights triggers a period of muscle growth that lasts for up to 48 hours, but to take advantage of that opportunity, you also need to be on point with your diet. Norton found that when we eat a meal with enough protein in it, it triggers a surge of muscle growth that gradually slows down over the course of around six hours, like so:
This isn’t just “potential” muscle growth, this is your body actually constructing muscle. That means that if you eat three meals per day, you’d be having muscle growth spurts that look something like this:
Already we can see that skipping a meal is a missed opportunity for muscle growth:
This Nortonian model of muscle growth brings up some questions. First of all, if you miss a growth opportunity, can you make up for it later by eating a meal that has extra protein in it? For example, what if we could do something like this:
Unfortunately, catching up is not possible. Norton’s research has proven that muscle growth is maximally stimulated with around 40 grams of protein. If you have more than 40 grams of protein in a meal, no additional muscle growth is triggered. So if you skip a meal, or eat a meal with too little protein in it, there’s no way to make up for it by eating more protein in the next meal. This means that it’s better to spread your protein intake out over the course of the day.
Note: it’s fine to eat more than 40 grams of protein per meal. If you have more than 40 grams in a meal, that’s perfectly fine, and that might be needed in order to hit your daily macro goals, but it won’t trigger extra muscle-protein synthesis.
Note: 20 grams of protein still stimulates a lot of muscle growth. While eating 40 grams of protein per meal will get you the absolute ideal amount of muscle growth (100%), eating just 20 grams of protein will get you most of the results (80%). If you don’t hit 40 grams of protein in every meal, that’s fine, just make sure to get at least 20 grams.
For example, it’s common to have more protein with dinner than with breakfast, so a common way to distribute your protein over the course of the day might look something like this:
The breakfast will still produce good muscle growth, and that large amount of protein with dinner will still be fully digested. It’s not perfectly ideal, but it’s pretty good. If you wanted to 100% maximize your muscle growth, though, you’d move 20 grams of protein from dinner to breakfast, giving you at least 40 grams in each meal.
How Often Can You Stimulate Muscle-Protein Synthesis?
This raises another question. How often can we stimulate muscle protein synthesis? Could we eat protein all day long, perpetually maintaining peak muscle growth conditions? What about something like this?
Layne Norton tested this idea and discovered that we can only trigger muscle growth once every four hours or so. If we eat meals more frequently than that, again, the protein will contribute towards our daily macros, but the meals won’t stimulate extra growth via muscle-protein synthesis.
This leaves us with an ideal meal schedule that looks something like this:
How controversial is this research? Could it be wrong? While there are still some questions about this theory, most of them are finer details, not issues with what we’ve discussed above. One of those finer details is that these spurts of muscle growth seem linked to one specific component of protein (leucine), not our overall protein intake. Dr Stuart McGill’s research has shown that some protein sources have more leucine than others, so it’s not quite as simple as just making sure to eat 40 grams of protein (study). For example, you can get maximal muscle growth with just 27 grams of whey protein, whereas you might need more like 50 grams of rice protein in order to get the same effect.
However, Norton’s overall research isn’t controversial. In fact, it’s the dominant theory among the top researchers in the field, including both Dr Eric Helms and Dr Brad Schoenfeld. To quote Schoenfeld:
The anabolic effects of a meal last a maximum of 6 hours or so. Thus, consumption of at least 3 meals spaced out every 5 to 6 hours would seem to be optimal for keeping protein synthesis continually elevated and thus maximizing muscle protein accretion. This hypothesis needs further investigation in a controlled long-term study.
Now, one discrepancy to note is that Norton recommends eating every four hours, whereas Schoenfeld recommends eating every 5–6 hours. While their recommendations are slightly different, their understanding of the research is not. Norton is simply erring on the side of eating more often, whereas Schoenfeld is erring on the side of eating a little bit less often. They’re both giving advice based on the same understanding of the science.
How Do Lifting and Protein Distribution Fit Together?
Both lifting and consuming protein increase muscle protein synthesis. We’re talking about the same phenomenon in both cases. After a good workout, muscle-protein synthesis will shoot up and then slowly decrease over the course of a few days. Eating a meal that’s rich in protein has a similar but milder effect that lasts for just a few hours.
If you consider that you’re going to have extra growth potential immediately after training, does that mean you should be eating extra protein post-workout? Yes. Some recent research is showing that after a hearty full-body workout, there’s a benefit to having some extra protein.
So you might consider your ideal workout day to look something like this:
This is a pretty classic bodybuilding diet, where you eat 4–5 meals per day and have an especially big post-workout meal. Fairly simple, and fairly ideal.
Does this mean you should be eating 4–5 meals per day? Yes, but keep in mind that they don’t all need to be massive meals. You can trigger muscle growth just as easily with snacks, such as a bit of greek yogurt, a protein bar, a protein shake, or some cottage cheese. These snacks should actually make your overall diet easier, as they will allow you to have a smaller breakfast, lunch and dinner.
However, don’t worry if you can only eat three meals per day. Just have breakfast early, have dinner late, and make sure that all of your meals have at least 20 grams of protein in them. It won’t be perfectly optimal, but that way you’ll spend most of the day with boosted muscle growth.
But what about growth hormone? The main muscle-building advantage of intermittent fasting is often said to be growth hormone, and if we’re eating steadily throughout the day, we’re missing out on having elevated growth hormone during our fasted periods. So, should we eat more often to get more muscle-protein synthesis, or should we fast to get more growth hormone?
Let’s compare the two overall approaches.
Intermittent Fasting vs Traditional Bulking
We’ve looked at the muscle-building advantages of intermittent fasting, with the main advantage being that you’d produce more human growth hormone. We’ve also looked at the muscle-building advantages of eating more frequently, with the main advantage being that you’d stimulate more muscle growth more often.
Which advantage is greater? Researchers have compared different meal schedules and concluded that having several meals spread out over the course of the day builds more muscle than intermittent fasting (study).
Eating 3–6 meals per day is ideal for muscle growth, especially if you’re skinny. However, once again, the difference is going to be very small. So small that it may not even be noticeable. In fact, some studies comparing intermittent fasting against a more normal meal schedule found identical amounts of muscle growth (study).
Eating more frequently may result in leaner gains. Since the amount of calories you eat determines the amount of weight you gain, and since intermittent fasting reduces muscle gain, this means that while the overall amount of weight you gain in either situation will be the same, you’d theoretically gain less muscle and more fat with intermittent fasting.
Eating more frequently makes it much easier to eat enough calories. And keep in mind that if you have a smaller stomach or faster metabolism, eating more frequently is absolutely essential while bulking. Your stomach simply won’t be able to handle the massive meals of an intermittent fasting bulking protocol. (We’ve had members attempt this and wind up giving themselves acid reflux.)
The Best Types of Intermittent Fasting for Bulking
By now it should be clear that we don’t consider intermittent fasting to be ideal for bulking. However, nutrient timing isn’t that big of a factor when it comes to muscle growth. If your workouts, diet, protein intake and sleep habits are all good, you can make good gains with anywhere from 2–7 meals per day.
This means that intermittent fasting is still a valid option, even while bulking. Furthermore, some intermittent fasting diets take some of our criticisms into consideration.
Using BCAAs to stimulate muscle protein synthesis. The main disadvantage of fasting while bulking is the lack of muscle protein synthesis. However, what if it were possible to stimulate muscle protein synthesis while fasting? This would allow you to get the best of both worlds, right?
Supplementing with leucine or branched-chain amino acids (BCAAs) sort of allows you to do that. They contain enough of the amino acid leucine to trigger muscle-protein synthesis, but they contain so few calories that Martin Berkhan still considers it fasting. The downside is that since you’d still be in a calorie deficit, there wouldn’t really be any muscle growth going on. (The strategy works better while cutting, as the BCAAs prevent muscle loss and improve workout performance.)
Fasting just once per week? There are also types of intermittent fasting where you only fast for one 24-hour period each week. The most famous version of that is Brad Pilon’s Eat, Stop, Eat approach, and that’s also the approach Dr John Berardi used when testing out an extreme bulking plan on the fitness blogger Nate Green (Bigger, Smaller Bigger).
There are three benefits to doing 24-hour fasts. The first is that they give your digestive system a total break from the stresses of overeating; the second is that you get to burn a little bit of fat right in the middle of your bulk; the third is that if you’re only fasting for one day each week, then you’d be growing at full speed 86% of the time. That’s a big improvement compared to 16:8 fasting, where you’d only be growing at full speed for around 67% of the time.
There are also two downsides to 24-hour fasts, though. First, you won’t be building muscle on the day that you’re fasting, and this will slow your results down. Second, it can be extremely unpleasant for some people.
If you want to experiment with 24-hour fasts, I recommend scheduling them as far after your workouts as possible, where there wouldn’t be much muscle growth taking place anyway. For example, your week could look like this:
Monday: full-body workout
Wednesday: full-body workout
Friday: fully-body workout
So. daily 16-hour fasts or weekly 24-hour fasts? From a results perspective, I think 24-hour fasts are a more logical approach. Your digestive system will enjoy the break, you can schedule it far away from your workouts, you might actually lose a decent amount of fat, and it won’t slow your results by very much.
However, from a lifestyle perspective, most people—especially guys in their 20’s—seem to prefer 16-hour fasts. They quickly get used to skipping breakfast, and they often find that it helps them be more productive in the morning. The 24-hour fasts, on the other hand, can be quite unpleasant, even for young guys who are good at following intense diet protocols.
The Skinny Guy’s Bulking “Fast”
Okay, so we can see that there are two significant advantages to intermittent fasting while bulking, namely:
- Our digestive system gets a break from overfeeding. Bulking diets can be brutal on skinny guys. There are just so many damn calories that it can feel like a relentless assault on our stomachs and energy levels. Taking a day off each week where we don’t eat any calories can be a welcome break.
- Skipping breakfast is pleasant and productive. Most skinny guys wake up without much of an appetite, making breakfast more of a chore than a treat. Moreover, eating a big breakfast can use up our morning energy on digestion, especially if we have weaker digestive systems (and many of us do).
However, there are also two major downsides to intermittent fasting:
- Less muscle growth, more fat. When you’re fasting, your muscles aren’t growing. This will not only slow down your muscle gains, you’ll also gain more fat.
- Intermittent fasting makes eating enough to gain weight way harder. It’s hard enough to eat a bulking diet when you’re eating 3–5 times per day. Cram those calories into a couple of meals over the course of a few hours and it becomes downright brutal. Who wants to eat a 1,500-calorie lunch? Lots of people, sure, but I’d rather stick a fork in my eye.
So, how can we min-max our results based on all of this research? I have two protocols that you might want to experiment with. Keep in mind that you’re always free to follow a traditional bulking diet, eating 3–5 regular meals per day. But if you find yourself wanting to experiment with intermittent fasting, here’s what I would recommend instead:
The Mini-Meal Reverse Cheat Day
24-hour fasts allow your digestive system to take a break, and it might give you a chance to lose a little bit of fat right in the middle of your bulk. That’s great, but we can accomplish all of that without any fasting whatsoever.
Instead of fasting once per week, we recommend having a “cheat day.” But instead of doing the fat-person cheat day, where you eat extra food, we recommend doing the skinny guy’s cheat day, where you eat less food. You can still eat several times per day, just keep your protein intake high and your calorie intake low. Your digestive system will love the break, and you’ll lose some fat. (This is how Jared gained 33 pounds in three months, as shown above.)
You’d have a meal schedule something like this:
Monday: full-body workout, eat big
Tuesday: rest, eat big
Wednesday: full-body workout, eat big
Thursday: rest, eat big
Friday: fully-body workout, eat big
Saturday: rest, eat big
Sunday: take a break from eating big
The Light Breakfast
Skipping breakfast increases morning productivity, but you miss out on an opportunity to stimulate muscle growth. One solution is to have a protein-rich breakfast that’s smaller and lower in calories.
This light breakfast could be a protein shake and some fruit, a protein bar and a latte, or even just a smoothie. All of those will be quite easy to digest, they aren’t very filling, and they can contain at least 20 grams of protein. The meal will be light enough that you’ll still be productive, you won’t fall too far behind on calories, and you’ll kick-start some morning muscle growth.
These half-fasts are what Dr Layne Norton recommends to bulkers who are curious about intermittent fasting:
If you want some of the benefits from intermittent fasting but want to optimize muscle mass, I would advise a different type of fast. Rather than cutting out all calories, simply restrict carbs and fats during your fasting window, but continue to evenly distribute your protein intake throughout the day.
Take this approach, and you are still going to get a large volume of food in the feeding period and spend a large portion of the day in a low-insulin fat-burning state, but you’ll be able to distribute protein in such a way that is better for muscle growth.Layne Norton, PhD
This is what we recommend to our members, and this is how I managed to gain 55 pounds over the course of a couple of years:
Most of the bad rumours about intermittent fasting are false. You won’t lose muscle while fasting, it won’t tank your metabolism, and your body won’t have any trouble digesting 80+ grams of protein per meal.
Moreover, many of the benefits of intermittent fasting are true. For example, intermittent fasting really will allow you to naturally produce more growth hormone, and it really does help people maintain more muscle mass while cutting.
However, intermittent fasting is still bad for bulking. Intermittent fasting is designed to help overweight people lose weight and still feel satisfied by eating large meals. It also helps people burn fat while retaining the muscle they’ve already built. But intermittent fasting is not helpful for skinny guys trying to bulk up because it makes it harder to eat enough calories, it limits muscle growth during the fasting period, and the main advantages don’t help with muscle growth anyway. As a result, intermittent fasting is not a great approach for people who are trying to prioritize muscle gain.
Just to further emphasize how consistent researchers are with their opinions on intermittent fasting, here are the researchers over at Examine.com weighing in with their bulking advice:
Meal frequency is a topic of much debate. For decades, “six meals per day” has been a bodybuilding mantra, but now the intermittent-fasting crowd claims we can be awake for hours, even a whole day, without eating a bite — and be healthier for it!
The truth probably lies somewhere in the middle.
Skeletal muscle protein synthesis changes with amino acid concentrations in the blood; our bodies become desensitized to the anabolic stimulus of protein after about three hours. Eating too frequently can therefore impede muscle protein synthesis.
On the other hand, you don’t want to deprive your muscles of the amino acids they need to grow. Since a moderate-sized meal might take up to 5 hours to be digested, it seems prudent to eat something every 4–6 hours, which translates to 3–4 meals per day (study, study).Examine.com
So there we have it. Intermittent fasting is great for cutting, but if you want to build muscle as quickly and leanly as possible, it’s better to eat 3–5 meals per day.
Update 2019: the Tinsley Intermittent Fasting Study
A new study on intermittent fasting by Tinsley et al. just came out. They compared muscle growth between different groups of women, some of whom were eating steadily throughout the day, others who were intermittent fasting (using a 16:8 protocol). What’s interesting is that these women were bulking on a modest calorie surplus of around 200 extra calories per day, and there were no differences in muscle growth between the groups. This seems to show that, at least with slower rates of weight gain, intermittent fasting doesn’t reduce our ability to build muscle while bulking.
I reached out to Eric Trexler, PhD, for his thoughts on what to make of this for guys doing a bonafide bulk (eating in a larger calorie surplus and gaining closer to a pound per week). He told me the following:
It’s certainly possible that results could’ve been different if they pushed for a particularly rapid rate of muscle gain, but we can’t be sure. There are certainly some downsides of IF, and I don’t see a ton of utility when it comes to bulking. The primary benefit seems to be satiety management when caloric intake is low. I can’t imagine intentionally nudging somebody toward time-restricted feeding unless they were struggling with hunger, or simply couldn’t accommodate more meals into their eating schedule due to timing/logistics.
As noted in the [Monthly Applications in Strength Sports] article, it is interesting that interventions don’t seem to show a detrimental effect on hypertrophy. Based on the research to date, I’m left to assume that the robust effect of resistance training on 24-hr protein synthesis is essentially “washing out” the small benefit of more carefully scheduled protein feedings for initiating frequent spikes in muscle protein synthesis. However, I think the “default approach” for bulking would still be shooting for 3-5 meals spaced throughout the day.
And as more research comes out on the topic, I feel less and less confident telling someone that they’re making a huge mistake by adopting a time-restricted feeding window, from a muscle retention/hypertrophy perspective.
As far as my own take on this, I think I might need to adjust my graphs to show a larger boost in muscle-protein synthesis from lifting weights and a smaller boost in muscle growth from individual meals. I think that’s going to give us a clearer visual representation of how intermittent fasting affects muscle growth while bulking.
I’ll keep my eye on the research to see what else happens. Intermittent fasting remains popular, so I think we’re going to have plenty of new studies coming out, hopefully with some of them conducted on men who are bulking up more quickly.