by Siim Land
The general consensus is that you can only absorb 30 grams of protein per meal and you need to spread your protein intake across 4-6 meals to maximize protein synthesis over the 24-hour period. However, it doesn’t mean that eating fewer meals with higher amounts of protein would make you waste away that protein. Humans in nature wouldn’t have a steady intake of protein either yet they function perfectly well.
Amino acids and some peptides are able to self-regulate their time in the intestines. For example, the digestive hormone cholecystokinin (CCK) can slow down the contraction speed of intestines in response to protein intake[414]. CCK gets released when you eat dietary protein and it slows down your digestion as to absorb it better[415]. See Figure 62.
Figure 62 CCK controls gallbladder contractions
If you were to absorb protein too quickly, your liver wouldn’t be able to maintain a steady stream of amino acids into the blood over the 24-hour period because you’ll burn them all for energy.
Even if you’ve eaten a large piece of steak with over 60 grams of protein, you wouldn’t be converting those amino acids into energy immediately anyway. Because of CCK and the generally slower speed of digesting steak, the protein from that steak will be digested over the course of many hours and your body will slowly assimilate those nutrients without wasting them away.
A Mayo Clinic study found that, on average, it takes about 24-35 hours for food to fully travel through the digestive tract and be completely absorbed[416].
As soon as you consume something with calories, you’re entering into a fed state and your body’s going to be breaking down that food.
After a few hours of digestion, your body goes into the post-absorptive stage, wherein the nutrients of the last meal are still circulating the bloodstream. This can last up to 8-12 hours and that’s when you’ll truly enter a fasted state.
Our intestines will contract according to the speed at which it can digest food. If they can’t handle any more protein, then they won’t waste this precious resource away but will simply slow down gastric emptying. After a few moments, when you’ve digested the protein you already consumed, the intestines will then move the remaining protein down the line so to say and continue absorption.
If you eat more protein than your body needs right now to trigger protein synthesis, it slows down the digestion of the excess and then gradually releases the amino acids into the blood over the course of the coming hours when your protein synthesis gets lower. Some amino acids can even be temporarily stored inside muscle cells for future use whether for maintaining amino acid homeostasis or for energy production.
The reason it’s thought that you can only absorb 30 grams of protein in one sitting is that you only need about 20-30 grams of protein to trigger muscle protein synthesis and actually build muscle[417]. Any more than 40 grams doesn’t stimulate MPS further. See Figure 63.
Triggering muscle protein synthesis is mostly regulated through leucine, which is the main anabolic amino acid. It requires about 2-3 grams of leucine to activate MPS and generally, you can get that amount of leucine from 20-30 grams of a complete protein. That’s where this rationale originated from.
Figure 63 Muscle Protein Synthesis Peaks at 20-40 grams of protein
However, this doesn’t really tell you much about how much protein you can end up absorbing in one meal. It just tells you that if you want to keep the muscle building signal activated more frequently then you’d have to spike muscle protein synthesis more frequently as well. There’s no indication of how it affects muscle protein synthesis over the 24-hour period.
However, the stimulation for muscle growth after resistance training will remain elevated for a long period of time. Studies have found that the potentiation of exercise-induced increases in myofibrillar protein synthesis and Akt/mTOR signaling by protein consumption is sustained for at least 24 hours post-workout[418]. Even if you stimulate MPS twice within those 24 hours compared to 6 times you can still build muscle if you eat enough protein within that time frame.
Additionally, more frequent spikes of protein synthesis won’t necessarily mean more muscle growth either because if you just eat 30 grams of protein then there aren’t many amino acids in that small meal to build new tissue either. If you were to eat that large steak again with 60 grams of protein, you’ll activate protein synthesis and you’ll have more than enough building blocks as well. So, in theory, it could be that less frequent spikes in muscle protein synthesis but with a higher amount of protein could potentially build more muscle just because of the higher availability of amino acids that could be absorbed much more efficiently.
Eating fewer meals and consuming more than 30 grams of protein in one sitting with intermittent fasting has not been shown to have any negative consequences in terms of lean tissue maintenance. One study done on women who ate their daily protein requirements of 79g of protein in either a single meal or 4 meals saw no difference in terms of protein metabolism and absorption[419].
Several intermittent fasting studies have also shown that eating your entire days' protein in a 4-hour eating window has had no negative effects on muscle preservation[420][421][422][423]. When it comes to body composition and fat loss, then meal timing has been shown to be irrelevant as intermittent fasting doesn’t slow down your metabolism or make you lose muscle.
Recent research indicates that, when fasted, we can use up to 3.5g/kg/day of protein and breakdown and metabolize up to 4.3g/kg/day[424]. This makes sense in an evolutionary context where would be primed to use a lot of protein after going without and then making up for lost time after a successful hunt.
Like I mentioned, eating 4-6 small meals a day may elevate muscle protein synthesis more frequently, but more frequent surges of muscle protein synthesis won’t necessarily mean more muscle growth because what matters most is how much protein your body ends up absorbing over the course of the 24-hour period. If you’re doing intermittent fasting with 2 meals a day, you can spike muscle protein synthesis twice a day and that’s going to be more than enough to force your body to grow. What matters more for muscle growth is the training stimulus and adaptive signal.
In fact, being in a fasted state makes you more protein sparing and anti-catabolic by increasing growth hormone and ketones. Higher levels of growth hormone and IGF-1 can stimulate muscle protein synthesis and it definitely improves the body’s sensitivity to protein intake[425]. You’ll end up absorbing your food better because it’s perceived as more scarce.
How to Increase Protein Absorption
It’s not about how much protein you put into your mouth and eat. It’s about how much protein you absorb and how many of those amino acids get used for your goals.
The reason some people need to consume ultra-high amounts of protein to build muscle is that they’re not able to assimilate it effectively and it’s simply a waste. You want to eat as little protein as possible to get as much effect as you can.
Here’s what to do to increase protein absorption with intermittent fasting:
Exercising before food will also deplete your body’s glycogen stores which makes the muscle cells more eager to absorb carbohydrates from food. Every food that’s used for recovering from exercise will be prioritized much higher for both muscle growth and maximal absorption.
Before eating you want to create an acidic intestinal environment by stimulating the production of hydrochloric acid (HCl) in the gut. Foods high in HCl are lemons, celery, olives, and vinegar. Warm lemon water with apple cider vinegar is great for blunting the blood sugar response of eating and helps with digestion. Ginger, in particular, helps with protein absorption.
Before eating you also want to put yourself into a parasympathetic state and become relaxed. If you’re stressed out or are feeling anxious, then your adrenals will direct blood flow away from the gut into the extremities. This is going to shut down digestion and promotes constipation. That’s why never eat when you’re stressed out and always sit down with your meal. Chewing your food is also
incredibly important because it’s going to make it easier for your gut to absorb it. Don’t eat on the run and always be mindful of what you put into your mouth.
Pre-biotics are plant fibers that travel through the intestines unchanged and they help with digestion by feeding the bacteria in your gut. Pre-biotic foods you should eat as the first part of your meal are garlic, onions, asparagus, leeks, artichokes, dandelion, chicory root, and green bananas.
Probiotics promote the creation of live bacteria in your gut that are going to help with breaking down the nutrients from your food. They’re microorganisms that are going to influence your mood, your immune system, your cognitive functioning, and body composition. Therefore, you want to maintain a healthy gut flora by eating fermented foods like sauerkraut, pickles, kimchi, olives, miso, raw kefir, and even very dark chocolate.
Combining large amounts of protein with starches and carbohydrates are also going to inhibit the digestion of those foods because they require different digestive enzymes. That’s why animal foods are best eaten with just vegetables and fermented foods. If you do eat starch then it should be easily digestible cooked starch like sweet potatoes, white potatoes, white rice, or buckwheat.
Slow walking after your meal is also going to lower the blood sugar response from what you ate and helps with digestion. It has to be a very slow and peaceful stroll because if you become too sympathetic you’ll shut down the digestion again.
The over-arching message is that when it comes to protein or any other type of food, you want to eat food that’s going to support a specific goal whether that be health, muscle growth, or performance. Just eating large amounts of protein or whatever macronutrient just for the sake of eating it is a waste. That’s why you want to absorb more nutrients from eating less instead of simply burning off calories.
Should You Consume Protein Before Working Out
In the case of wanting to maximize the anabolic effects of consuming protein, of course, you’d want to have slightly more frequent episodes of elevated protein synthesis just due to the fact that if you’re in an anabolic state you’ll build more tissue.
When you’re doing resistance training, then you’re inducing damage to the muscle cells and tissues. If you consume adequate protein after the workout, you’ll be able to heal that damage and hopefully result in sarcoplasmic hypertrophy.
However, when working out fasted you have limited amino acid availability and thus are subject to increased muscle damage. That may not be ideal for someone trying to build more muscle because they may end up with a NET negative muscle homeostasis.
Fasting itself is already a pro-catabolic stressor. Adding training on top of that and then being forced to consume all of your daily protein within a small time frame is indeed like pushing a boulder up a hill.
The amounts of protein you can absorb in one sitting is arbitrary for maintaining lean tissue but it’s probably not optimal for positive NET growth. That’s why having some amino acids circulating the bloodstream during the workout will not only minimize the muscular damage but will also promote additional muscle protein synthesis after training.
Hoffman et al. (2010) found that 42 grams of protein consumed immediately before and after a strength training session improved recovery in strength trainees compared to a maltodextrin placebo[426]. Unfortunately, energy intake and nutrient timing weren’t equated between these 2 groups so it’s hard to identify what caused the faster recovery. It might have been the caloric surplus, protein timing or the supplementation itself.
Studies by Brad Schoenfeld and Alan Aragon (2017) haven’t seen any significant differences in muscular adaptations when consuming protein either pre- or post-workout[427]. However, these studies aren’t probably done on subjects who exercise fasted. If you’ve eaten something a few hours before training, you’ll have plenty of amino acids circulating the blood which will then be used for energy. That’s why if you’ve had a real meal pre-workout it’s not necessary to be taking any protein shakes or the like. Intermittent fasting throws a monkey wrench into the spokes of most studies because it puts the person into a different metabolic state.
Despite the catabolic factor, fasting has many physiological benefits if not on muscle growth then at least on longevity and general health. However, there are still some advantages to working out fasted
Consuming carbohydrates and raising insulin suppresses lipolysis and fat burning during exercise[428]. You’d have to burn through those carbs first before getting access to your adipose tissue. Whether or not it matters is subject to context and the goal of that particular training session.
Training fasted improves glucose tolerance and improves insulin sensitivity[429], which doesn’t help with muscle growth directly but it’ll help you to stay leaner while building muscle.
Fasting increases blood flow in abdominal subcutaneous fat, which can help with losing that stubborn belly fat. A 3-day fast increased abdominal subcutaneous blood flow by 50%[430]. However, this change is minute and probably not relevant.
Fasted resistance training causes a bigger anabolic response to eating post-workout than fed training by increasing the p70S6 kinase[431]. Theoretically, you’ll create a bigger super-compensatory effect for muscle hypertrophy by working out while fasting and then refeeding properly.
Increased growth hormone from working out fasted may help to preserve lean muscle and protect against excessive catabolism[432]. This may be worthwhile if you’re eating at a caloric deficit but still getting more than enough protein. At other times, it would depend on what macro ratios you eat.
Even Muslim bodybuilders who workout during Ramadan haven’t seen any decrease in muscle or body composition[433], despite working out hard and even during dry fasts. They may train differently than normal but it comes to show how more advanced trainees can even workout fasted.
However, in most people, fasted exercise leads to a decrease in performance. It’s natural to feel weaker and slower if you haven’t eaten for too long. That can cause mental fatigue, lethargy, and lower your workout results. At the end of the day, if you’re able to work out harder, then you’ll be able to burn more fat and build more muscle, which then helps you achieve a better body composition. If fasting gets in the way of that, then you need to adjust your approach.
Ramadan style fasting has been shown to decrease anaerobic performance and power output[434]. High-Intensity Training modalities like CrossFit, P90X and Tabata intervals can stop muscle growth and repair processes by down-regulating mTOR through AMPK activation. It’ll also cause further muscle fiber teardown, which adds an additional catabolic stressor to the body[435]. In that case, increased AMPK and autophagy actually protect against muscle degradation by promoting cellular turnover and lean muscle maintenance[436].
Although working out fasted limits your performance slightly it can only hinder your potential to a certain extent. In reality, the difference will only be like 5-15% which isn’t detrimental nor always necessary. You don’t need to be performing at 100% of your maximum every workout to see results or to get stronger. In fact, most people will get as good of a physique in spite of that minor limiting factor.
There’s this dichotomy between wanting to fast longer during the day and trying to build lean muscle mass with it.
To maximize the autophagic benefits of fasting, you’d want to fast for as long as possible every day. In most cases, that would entail about a 20-hour fasted window.
For optimal muscle growth, you’d want to have a smaller amount of amino acids and protein in your system before working out.
For better body recomposition and nutrient partitioning, you’d benefit more from backloading most of your calories into the post-workout scenario where your body prioritizes recovery, not storage.
This gulf of wanting to build muscle while trying to fast for as long as possible even before training is quite difficult to breach. However, it’s possible with something I call Targeted Intermittent Fasting (TIF).
Enter Tar
geted Intermittent Fasting
You don’t need to be consuming any calories all the way up until the point you’re about to do resistance training. At that moment, you’d want to have some protein and amino acids to protect you against excessive catabolism.
To minimize time spent in a fed state, the fastest and most efficient solution would be to consume a protein shake with about 20-30 grams of protein immediately before or during the workout. This will promote recovery and muscle growth despite having fasted for that long beforehand.
Here’s what the Targeted Intermittent Fasting Protocol looks like:
Fast for the majority of the day as long as you can before working out.
Consume only water and zero calorie teas or coffee all the way up until 18-20 hours of fasting.
When starting to workout at 18-20 hours, consume a protein shake with 20-30 grams protein. It’s preferable to drink it during the actual workout and use quality protein powders that don’t have artificial sweeteners or other additives.
While working out, focus on heavier compound movements and hypertrophic exercises to stimulate muscle growth. In between your sets, sip on the protein shake.
In the post-workout scenario eat the rest of your calories within 2-3 hours or in a single meal. Make sure you still get enough protein after training.
This is what I call the Targeted Intermittent Fasting protocol inspired by the targeted ketogenic diet approach wherein you consume a small amount of carbs during high-intensity training. The idea is that you’ll be consuming protein and calories only when your body needs them. At other times you’re much better off by fasting because of deepening autophagy and ketosis. This sort of nutrient timing will yield positive effects on muscle growth as well as reaping the benefits of being in a fasted state. It can breach the dichotomy without missing out on potential growth.