It might not be a secret that adding protein to your diet is important for maximizing your strength-training efforts.
As when Ashton Eaton, 2x Decathlon Olympic gold medalist. recently responded to the benign question, “what is your diet?” on Quora concisely highlighting his first principle,
“Protein is king.”
But for those looking to maximizing their results, it pays to go deeper. There is a lot to learn about your protein intake, and diving into the research on protein dosing, source, and timing can lead to fruitful experimentation and better results.
One aspect of protein that might be less appreciated are the roles each individual amino acid play during muscle protein synthesis (MPS). One amino acid worth discussing in detail is leucine.
According to a recent critical review in The Journal of Nutrition about amino acid digestion and muscle protein anabolism, leucine seems to act as a trigger for amplifying protein synthesis.1 If you want to maximize your body’s ability to rebuild muscle after exercise, you’ll need to hit your leucine threshold to trigger mTORC1-activated MPS. Here’s how.
Your Body’s Needs for Building Proteins
To build muscle, your body needs to replace and grow new cells. Growing new cells requires the production (synthesis) of new proteins to do the work of replication and energy production. And taking a relatively simplified view, this process has two essential requirements:
- Enough energy to undergo and complete the process of synthesizing new proteins, and
- A high enough concentration of the amino acid “building blocks” of the proteins you’re going to synthesize.
The body is constantly experiencing “protein turnover.” This simply means that new proteins are being produced while old proteins are being broken down.
Comparing the rates of these two processes sheds lights on whether muscle tissue is growing (if synthesis is greater than breakdown), or muscle tissue is shrinking (breakdown is greater than synthesis).
The act of exercising, and in particular weight training, stimulates MPS regardless of your protein intake. During high intensity resistance training, your body largely shuts down the process of MPS in order to increase blood flow and supply muscles with the energy they need to perform the task at hand.
During this time, as blood flow increases, amino acid flux increases. This means, as you use your muscles for extended periods of time, your body harvests protein from existing muscle tissue. The concentration of available amino acids in your blood stream increases.
In the period just after resistance training (0 – 1 hour), muscle tissue becomes more sensitive to nutrition and gradually shifts from net negative protein turnover to net positive; i.e., MPS increases.
This happens during exercise even in a fasted state. So why eat protein?
Protein extends MPS post-exercise. Adding protein, especially the essential amino acids not available through protein turnover and required from your diet, increases the duration of MPS and helps provide the body with the ingredients it needs to continue building muscle tissue for longer.
The Leucine Trigger
Leucine, in particular, acts as a strong trigger for protein synthesis.
mTORC1 (mechanistic target of rapamycin complex (1) is a protein complex with a role in controlling protein synthesis. Leucine plays a role in activating mTORC1 signaling. Thus, leucine helps directly trigger a key mechanism in the MPS pathway.
Eating protein that includes leucine can trigger MPS even in the absence of exercise. However, the effects are relatively transient when compared to post-exercise MPS.
Adding leucine to post-exercise protein increases MPS in a dose-dependent manner. That means, increasing leucine content increases mTORC1 signaling and thus increases MPS activation.
This occurs when protein consumption is relatively low. When total protein intake is low, the amount of leucine plays an outsized role in stimulating MPS compared to other amino acids. When protein intake is high, it becomes more like a trigger with a maximum threshold. This means, even if protein intake is high but leucine is low, your body won’t be maximizing MPS. Only when the leucine threshold is reached will your body fully stimulate mTORC1 signaling and maximize MPS.
Meet the Leucine Threshold for Maximum Results
I mentioned earlier that energy was required to build new proteins. This is true up to a point. But once you have enough energy, it was shown that adding additional energy to your diet does not increase post-exercise protein synthesis.(2)
This same concept has similarities to protein synthesis, as well.
Say you set out to build your dream home. You’ve got your blueprints ready. Now you just need some materials to start. Wood. Nails. Screws.
You start building. You will make progress as long as you continue to supply enough materials. The walls will get higher, and the home will take shape.
That is, until you run out of wood or nails.
Similarly, you need to have the basic building blocks in your diet in order to build proteins and grow muscle tissue.
If you have plenty of wood, but your nails run out, you similarly won’t make it to a complete home.
Likewise, if you have plenty of some amino acids, but not enough of some others, you won’t maximize your ability to synthesize new proteins. You need quality protein that has plenty of all required essential amino acids.
So just like in our home-building analogy, your home will get closer to reality as the amount of all of your required building materials increase together.
Until, of course, your home is complete.
When you’re finished, you’re finished. Extra wood and extra nails won’t help anymore.
Here, too, the similarities continue with your protein intake. MPS continues to increase by adding more leucine to your diet as long as it comes along with a balanced, quality protein of all essential amino acids. But once a threshold is reached, it won’t continue to provide additional MPS benefits forever.
This critical review states that the leucine threshold for maximum MPS is roughly 1.8 – 2.0 grams.
MPS continues to increase in a dose-dependent manner upon increasing leucine until this threshold. Consuming more has not shown to provide further gains.(3) In the words of the study’s authors, activation of mTORC1 through leucine appears to act more like an “on/off switch” as opposed to a “dimmer switch.” However, if protein quality is low, leucine supplementation can amplify mTORC1 activation.
Optimization Through Personalization
In addition to other interesting information on protein dosing and timing that is worth reading in this review, one final interesting note pertains to the individualized way in which we respond to protein intake and MPS.
Their review highlights a large variability in individual response to protein and amino acid quality on lean mass growth and fat free mass growth. Some individuals respond extremely well to adding protein to their diet for stimulating MPS, while others appear to be “non-responders.”
Another interesting area of ongoing research is the desensitization of your muscle tissue to amino acid flux over time. For those all-too-familiar with plateaus and stalled progress, understanding your body’s response to repeated exercises may help direct your future workout plans.
For those looking to maximize muscle growth, its important to measure your progress. As the old saying goes, “you can’t improve what you don’t measure.” So track your growth, track your strength, track your protein intake, and analyze your findings to optimize your plan to meet your goals.
- Reidy, P. T., & Rasmussen, B. B. (2016). Role of Ingested Amino Acids and Protein in the Promotion of Resistance Exercise–Induced Muscle Protein Anabolism. The Journal of Nutrition, 146(2), 155–183. http://doi.org/10.3945/jn.114.203208.
- Glynn, E. L., Fry, C. S., Timmerman, K. L., Drummond, M. J., Volpi, E., & Rasmussen, B. B. (2013). Addition of Carbohydrate or Alanine to an Essential Amino Acid Mixture Does Not Enhance Human Skeletal Muscle Protein Anabolism. The Journal of Nutrition, 143(3), 307–314. http://doi.org/10.3945/jn.112.168203.
- Glynn, E. L., Fry, C. S., Drummond, M. J., Timmerman, K. L., Dhanani, S., Volpi, E., & Rasmussen, B. B. (2010). Excess Leucine Intake Enhances Muscle Anabolic Signaling but Not Net Protein Anabolism in Young Men and Women. The Journal of Nutrition, 140(11), 1970–1976. http://doi.org/10.3945/jn.110.127647.
When it comes to losing weight and getting a six-pack, not all types of cardio are created equal.
For example, doing low-intensity steady state cardio (such as jogging) can be great because it allows you to improve your lung capacity, burn some calories and get a euphoric feeling afterward (thanks to endorphins flooding your body). However, do too much of it and you can overtrain yourself and potentially even get an injury.
On the other hand, high-intensity cardio (such as sprinting) can also be great because you’ll burn tons of calories in a short amount of time, improve your speed and become more athletic. However, the risk of injury there is high, especially for beginners. Also, do too many sprints and some of the same issue as with the low-intensity cardio may arise.
Let’s get into both types of cardio and determine which one is best for weight loss.
First off, does cardio get in the way of muscle growth?
There is a common fear among the lifting community that doing cardio will either:
- Make you lose your muscle mass;Or..
- Make gaining more muscle mass hard or impossible to achieve;
There is some ground to these fears, but the context matters a lot.
Sure, if someone tries to run a 5k or 10k and reach a 300-pound squat at the same time, chances are, they won’t achieve either goal.
Specificity and the interference effect.
Specificity refers to your goal of improving something by practicing it more often. For example, if you want to become a great marathon runner, you need to run more. If you want to squat, bench and deadlift a lot of weight, you guessed it: train these 3 lifts more often.
If you try to improve too much at once, you’ll be mediocre at everything and never reach any goals you set.
The interference effect has more to do with the direct physiological impact cardio can have on your body’s ability to recover and build muscle. If you reach a point where you can’t properly recover because you’re doing too much cardio, you compromise your muscle-building efforts.
If you feel sore and fatigue from cardio by the time your next deadlift or squat session arrives, your performance will suffer and you won’t have very productive workouts.
But if you include cardio in in moderate doses and plan it around your weightlifting in a way that it doesn’t compromise your performance, not only will it not hinder your muscle growth, but it can also enhance it over time.
Is HIIT cardio better than steady state
There has been a fierce debate among people on whether HIIT cardio is better than steady state cardio. One side swears by sprints, the other one considers jogging and low-intensity cycling to be the holy grail of weight loss.
However, things aren’t so black and white and both types of cardio have their merit and can be effective, as long as you do them intelligently and within reason.
Let’s compare the two types and see the pros and cons of each:
Low-Intensity Steady State Cardio Pros:
1)When done in moderation, it is better for beginners as it carries a much smaller risk of injury.
2)It can burn a lot of calories if you do 20-60 minutes per session.
3)It improves your lung capacity which has a direct carryover to lifting weights and your daily life.
4)Low-intensity cycling hasn’t been shown to directly interfere with your strength.
Low-Intensity Steady State Cardio Cons:
1)You can burn yourself out if you overdo it.
2)You need to do at least 20 minutes to burn a noticeable amount of calories.
3)Jogging has been shown to impact lower body strength so it’s a good idea to plan it at least 48 hours before doing squats or deadlifts.
4)It can become boring and tiresome to do.
High-Intensity Interval Training Pros:
1)It’s a fun and challenging way to push yourself.
2)You can burn a good amount of calories in a short period of time.
3)It improves your speed, explosiveness, and overall athleticism.
4)It provides an afterburn effect for up to 24 hours after the session.
High-Intensity Interval Training Cons:
1)It carries a bigger risk of injury, especially for beginners.
2)It can impact your strength and performance on upcoming strength training sessions.
3)It’s more mentally challenging and doing it too often can lead to burnout.
As you can see, both types of cardio have their pros and cons and both can be the better option, depending on the context.
Is fasted cardio better than fed cardio
Before we delve into this, let’s first define the terms:
Fasted cardio is done on an empty stomach, but it goes a bit deeper than that and has to do with your body’s ability to process and absorb the food you eat.
You see, when you eat food, it gets broken down into various molecules that your body can use. The hormone Insulin is released and its job is to shuttle these nutrients into the cells. Depending on how big the meal is, your insulin levels can spike a lot and stay elevated for 6+ hours.
During the period when your body is digesting the food you’ve eaten, you are in a fed state (also known as a postprandial state). Once your body finishes digesting and absorbing the proteins, fats, and carbs you’ve eaten, your insulin levels drop to baseline and you enter a fasted state. Depending on your meal frequency, your body can move between a fasted and fed state multiple times within a day.
Also, having an empty stomach doesn’t necessarily mean that you’re in a fasted state. Your body may still be absorbing the nutrients from your last meal.
So, let’s recap:
- Exercise that is done when your insulin levels are at baseline is “fasted cardio”.
- Exercise that is done when your insulin levels are elevated and your body is processing the food from the last meal is “fed cardio”.
Now, there is a common myth that fasted cardio is superior to fed cardio for weight loss and there are two common arguments for that:
- Since insulin has been shown to suppress lipolysis (the breakdown of fat), it makes logical sense to do cardio in a fasted state when insulin levels are low. Theoretically, this would result in more fat being burned during the cardio session.
- In the morning, our glycogen (a form of energy that we store in our muscles and liver that the body can readily use for physical activity) levels are low and this should theoretically make the body more likely to go for fat mobilization to get the needed energy for the cardio.
These arguments make sense and from a first glance, it would seem that fasted cardio is superior to fed cardio for weight loss.
So where does this idea go wrong?
The prevailing argument against the superiority of fasted cardio is this:
Just because you burn more fat within each individual cardio session, doesn’t mean that you’ll burn more overall fat. There is a good bit of research out there that supports this argument.
For example, one study split 20 young women into two groups: one group doing fasted cardio and the other one doing fed cardio. Both groups were put on a 500 calorie deficit diet for 4 weeks.
The subjects completed either 1 hour of fed cardio, 3 times per week or 1 hour of fasted cardio, 3 times per week.
After 4 weeks, both groups had lost a significant amount of fat, but there were no noticeable changes between them.
This study suggests that as long as there is an established caloric deficit, doing either fasted or fed cardio won’t make much of a difference in the grand scheme of things.
You can check the full study for yourself.
The downsides to this study obviously are:
- The sample size is small. Only 20 women are participating.
- The study is a relatively short-term (only 4 weeks) one. If the researchers carried out the study for a longer period of time, maybe they would have seen one group starting to outperform the other, but we can’t know that.
From the research we have so far, we can conclude that there is no evidence that suggests one type of cardio being better than the other. More studies with larger groups of people and a longer duration should be made in the future to further prove or disprove the current consensus.
So, to recap:
- There doesn’t seem to be any special benefit to doing fasted over fed cardio if your goal is weight loss. Being in a caloric deficit is going to be the main driver of weight loss over time.
- Everyone should do cardio as it best suits them. Some prefer fasted cardio in the morning to start off the day happy and energized. Others prefer to do it in the evening, after having a few meals in.
Practical recommendations for cardio
With all of this said, let’s go over a few recommendations on how to do cardio for weight loss safely and sustainably.
Recommendation #1: Do cardio 3-4 times per week
Three to four cardio sessions per week is the sweet spot for most people. It allows some flexibility in your schedule, it doesn’t put too much stress on your body that you can’t recover well, it’s sustainable because it doesn’t take much willpower to follow through and it’s a nice change from a regular lifting routine.
Here’s an example:
Monday: 20 minutes of interval running
Wednesday: 30 minutes of stationary bike cycling
Friday: 30 minutes of jogging
Saturday: 20 minutes of cardio (bike ride outside)
Recommendation #2: Don’t go over 30-40 minutes per session, at first
As with everything else, you should ease into the process. If you’re just starting out with cardio, allow your body some time to get used to the stress before ramping up the numbers. Start off slow and build the habit of doing cardio consistently.
After a few weeks, start increasing gradually as you see fit.
But don’t go over 30-40 minutes per session in the first weeks.
Recommendation #3: Combine both low intensity and high-intensity cardio
As you already know, both high and low-intensity cardio is great for weight loss and health. Combining both types is great because it allows you to mix things up and keep things interesting. Here’s an example:
Monday: 10 sprints (HIIT)
Wednesday: 30-minute bike ride
Friday: 10 x 30-second running intervals at 70-80% intensity
With the above example, you’re combining very high intensity (sprints), low intensity (bike ride) and moderate intensity (interval running) types of cardio within each week. This is fun, engaging and each cardio session is different.
Recommendation #4: Do cardio on days where you don’t lift weights if your schedule allows
As we already discussed above, depending on the amount and intensity of the cardio you do, you can see some negative effects on your strength. For that reason, you should try and do cardio on days when you don’t lift weights. That way, you can keep the momentum going, develop a great habit of exercising daily and stay motivated.
Here’s a schedule:
Monday: Strength training
Tuesday: Low-intensity cardio
Wednesday: Strength training
Thursday: Interval running
Friday: Strength training
Alternatively, if you can’t make time for exercise every day, you can do cardio and strength on the same day, try to spread them at least 6 hours apart:
Monday: Low-intensity cardio (morning); Strength training (evening)
Wednesday: Interval running (morning); Strength training (evening)
Friday: Low intensity cardio/sprints (morning); Strength training (evening)