Fat Loss & Cognition with Phenylalanine & Tyrosine
Are these amino acids effective for fat loss & cognition?
Week 4 of researching each essential amino acid brings us to L-Phenylalanine.
L-Tyrosine, while not considered an essential amino acid, deserves mention in this article because it is produced from phenylalanine - in fact, half of the phenylalanine we consume is converted to tyrosine.
Both of these amino acids have extremely important indications for physical and mental performance because they are the precursors for adrenaline, noradrenaline, dopamine, and thyroid hormones - all of which are critical for energy and motivation.
These biomolecules are responsible for mobilization of adipose tissue (“fat”) for energy through multiple pathways and as a result have been studied for their ability to increase fat loss during exercise.
Tyrosine in particular is notable for improving cognition, especially under conditions of stress such as sleep deprivation or cold exposure. This one is a personal favorite I’ve seen excellent results with.
As usual, none of the research is yet definitive, but let’s investigate the current data on these potentially powerful amino acids.
Phenylalanine for Fat Loss
There are a few studies specifically looking at how phenylalanine effects fat oxidation during exercise. (1-3) The first of these studies looks at phenylalanine alone. (1)
In this first study, supplementing with phenylalanine before an hour cycling session at 50% VO2 max significantly increased fat mobilization based on significantly increased glucagon secretion compared to placebo. Glucagon is a hormone that mobilizes adipose tissue (fat) for energy. (1)
The second study found a significant increase in free fatty acids compared to placebo, again suggesting that the amino acids consumed pre-workout accelerated fat metabolism. (2) The third study confirmed the second study. (3)
The results are exciting, but these studies are not strong for several reasons.
First, they do not look at actual outcomes, e.g. body composition or weight changes with isocaloric control groups. It is one thing to increase hormones during training, or even improve body composition during the time period surrounding the exercise. But how does the body rebalance over the course of several days? Does the accelerated fat loss cause an accelerated fat gain in coming days, or increased hunger? Is muscle loss also accelerated? There are many questions unanswered that need further study.
Second, they are assessing hormone production which in theory should influence body composition, but biochemistry is not so simple and feedback loops typically prevent the “free lunch” effect. For example, if we increase one hormone now, such as glucagon, this creates a negative feedback loop: the hormone will drop later and its antagonist hormone, insulin, will rise. Glucagon breaks tissue down to increase blood glucose (to be used for energy), then insulin builds tissue by transporting glucose from the blood into cells.
Ultimately, changes in weight are dependent on energy balance, and changes in body composition are dependent on energy balance and net protein synthesis. Of course there are many nuances to that, but the general principal is we cannot conclusively extrapolate outcomes based on short-term changes in a single blood marker.
Third, the sample sizes are very small, 6 healthy young men in the first study, 10 in the others.
Fourth, they used a 60 minute steady-state cardio session. I would predict a different hormone response with a different type of training. In fact, I would expect this type of training to result in loss of muscle mass.
Fifth, they all share the same authors. This is in no way to discredit the data, but these are preliminary studies that need to be replicated by multiple labs and with larger population sizes.
Still, we can take this preliminary data with a grain of salt and experiment with phenylalanine around our training, especially given this is an essential amino acid required for synthesizing protein.
Tyrosine for Cognition & Performance
This is personally one of my favorite supplements for cognitive work and intense training sessions. I have experimented extensively with this amino acid in my own training and it lights me on fire.
But once again, you must be careful of negative feedback loops. If you accelerate the nervous system, it will decelerate later. In other words, if you train or study hard, you need to sleep and recover harder.
This goes for many things however and shouldn’t scare you away from learning more, including drinking coffee or even exercise itself. When you break the body down, it becomes stronger when it recovers.
Tyrosine is so important for our biology that 50% of the phenylalanine we intake is converted to tyrosine, and if we increase tyrosine intake we may decrease the need for phenylalanine (although it is still essential for other processes and we cannot synthesize phenylalanine from tyrosine, but we can synthesize tyrosine from phenylalanine). (6)
The body requires multiple B vitamins, magnesium, and iron, among other nutrients, to convert phenylalanine to tyrosine. By consuming tyrosine directly, we might save these nutrients while directly providing the substrate our body needs to produce catecholamines, dopamine, and thyroid hormones.
Tyrosine increases dopamine and norepinephrine in the brain, which results in improved cognition, focus, and motivation. Tyrosine has been found to be especially effective under stress (sleep deprivation, cold/heat exposure) or cognitively demanding tasks for promoting working memory & preventing cognitive decline. (5)
In general, tyrosine is also required for production of thyroid hormones. The thyroid regulates the metabolism in the body, and thyroid hormones are the switch that turn on energy production.
Tyrosine is found naturally in fish and meat - we can get 2 grams of it in a 6 ounce steak. Plant sources other than tofu are not great for this amino acid. The best you can get is 477mg from a cup of lentils, and that’s a filling serving of lentils for only half of the RDA. (4)
Summary
Based on the research I’ve read, I wouldn’t tout phenylalanine as a magic fat loss supplement, but it shows promise in preliminary trials for enhancing fat metabolism during training.
For reasons discussed in my Leucine & BCAAs article, I would certainly not supplement phenylalanine or any other essential amino acid in isolation.
Even if we put potential fat loss benefits aside, as an essential amino acid, phenylalanine is absolutely necessary for building muscle.
For performance purposes, we must ensure adequate intake of this amino acid to produce thyroid hormones, dopamine, and adrenaline. These are especially important for athletes who may have a higher demand for these hormones.
As for L-tyrosine, there may be direct benefits from supplementation for cognitive performance, especially under certain stressful circumstances. Personally, I have found incredible benefit from periodically supplementing with 1-2 grams of tyrosine. Some might find that to be a higher dose, and I do notice benefits with as little as 500mg, but many studies used far higher doses approaching 10 grams or more. (5)
While the research is not definitive (it often isn’t), in any case you need these amino acids for fundamental biological processes.
For physical or cognitive performance enhancement and maximizing training outcomes, you might have to experiment for yourself.
In strength,
Daniel J. Furtado, CPT, LMT, Owner of Honor Strength
www.honorstrength.com
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