Get Smart About Your Fitness with a Masterclass By Ph.D. Muscle Himself, Aaron Chacon

Aaron Chacon lifting weights in the gym

Rather hear a recap of some of Aaron's main points? Check out this video recap on YouTube!


In my more insecure days, Aaron Chacon would have been the kind of person I would have heavily resented. He's brilliant, puts the gods of Olympus to shame with his physique, and he's an incredibly kind person. Until I met him, I was all but convinced that being smart, buff, and kind was one of those situations where you could only pick two out of three at any given time. Aaron shattered that belief. 

New call-to-actionThere are hundreds upon hundreds of folks online who preach various messages about fitness and wellness (many of whom do so to either build their platform as influencers or to promote their own services) but while many know the mechanics of working out, very few have a comprehensive understanding of the science and mechanics that are foundational for getting in shape. Aaron, once again, is an exception. His Instagram handle and website domain sum it up well– he's the Ph.D. of Muscle. 

Aaron graduated from the University of Texas with a Bachelor of Science in Nutritional Science and a Bachelor of Arts in Dietetics before earning his Masters of Science in Nutrition Education from American University. Currently, he's focusing on his Ph.D. in biomedical and molecular pharmacology and nutrition science. On top of his education, he also has a background in a clinical setting where he specialized in nutritional counseling, IV-nutrition therapy, blood work analysis, and hormone replacement therapy.

Amidst his incredibly busy schedule, Aaron took the time to have a chat with me about some of the lessons he's learned along the way that anyone can use to approach their fitness regimen in a smarter way. 

(My portion of the conversation is in bold. His is in the standard font.)

I'll start with one of my favorite topics: supplements. Especially for people who are brand new to working out or who feel like they're under a time crunch, supplements are often marketed as easy solutions. There are thermogenics that claim to accelerate fat burning, suppress weight loss, or block your body from absorbing carbs; post-workout supplements that boast rapid muscle growth and acceleration; and pre-workout supplements that may or may leave you feeling like you chugged strawberry-flavored methamphetamine before heading to the gym.

All of that leads me to a couple of questions.

If someone is looking to use daily supplements to enhance their fitness progress, what should they keep an eye out for as something to avoid?

Aaron Chacon in the Lab

Well, this all depends (great answer, huh?). Truthfully, it'll come down to the person's goal. Most people probably want to lose fat at some point along their fitness journey - I'd argue that there is no supplement, or ingredient, that directly burns fat (excluding some drugs). I won't get into all the science behind fat loss here, but no supplement can push metabolism towards an increased flux through beta-oxidation (our principle fat-oxidizing pathway). Beta-oxidation involves 5 main steps, and you'll find supplements marketed for each. For example, the first step in B-oxidation involves "activating" and transporting fatty acids into the mitochondria where it's systematically broken down and used to generate ATP (our body's energy...kinda).

One of the most marketed supplements as a "fat burner" is L-carnitine - you see this stuff everywhere. Carnitine acts as a shuttle, moving fatty acids into the mitochondria for beta-oxidation. So, supplement companies perpetuate (the very ill-informed) notion that by ingesting more of this stuff, your body can pull more fatty acids into the mitochondria to be burned up for energy...or something like that. As you can imagine, this is a very simplified view of how things work in the body and as such, doesn't work at all. Just think about it - supplemental carnitine has to get from the stomach into the cell intact to work as claimed. Well, it's bioavailability is poor - I have yet to see a study demonstrating otherwise. Moreover, even when the stuff is infused via an IV, it still can't get into the cell. In fact, L-carnitine only seems to make its way into the cell through an insulin-mediated manner. You can use your imagination here, but it's not a strategy I'd recommend for most. 

Earlier, I very specifically mentioned that no ingredient directly burns fat (although I'd be eager to be proved wrong). There are indirect methods that may help, provided the person is maintaining a caloric deficit. Your body, first and foremost, doesn't want to lose body fat. Why would it? It's evolved in a way to maintain metabolic functions to support reproduction. It may be an odd way to think about it at first, but rest assured, that's its primary goal. When in a caloric deficit, the body has plenty of ways to regulate the conservation of energy. It's always easy to lose the first few pounds but gets increasingly more difficult as time goes on. Why is this? Well, it’s complicated, but I can give a few brief examples:

Your thyroid can be thought of as the master regulator of metabolism. When it’s functioning optimally, things move smoothly. As calories drop too low for an extended period of time, it flips a “hormonal switch”. It’s starts producing a mirrored form of the active thyroid hormone and puts the brakes on energy expenditure – it’s called reverse T3. As the levels of this rise, energy expenditure becomes less and less efficient – i.e. fat loss becomes increasingly more difficult. There are a few things that can trigger this in addition to too low of a caloric intake that also impacts the ability to lose fat. Unregulated cortisol (a stress hormone), for example, will make fat loss near impossible. Sub-optimal sleep is a very active area of research that ties in with circadian rhythm’s effect on metabolism. Point being – there are useful supplements that can help correct these issues.

So, my advice to someone trying to lose fat – stay away from the supplement store at first. Rather, assess your stress levels, quality and quantity of sleep, and while we’re at it, gut health (your diet is only as good as what you’re absorbing and utilizing). When I say assess, I’m not talking about how you feel – rather, everything I mentioned can be evaluated objectively through lab testing. If you feel something is off, don’ t let your subject perception take the place of objective analysis. By having some hard data in front of you, you can determine the right course to take supplement wise (and save you a lot of money and frustration in the process). So, thyroid support formulas (which usually contain fat-soluble vitamins, selenium, and iodine), cortisol-balancing supplements (ashwagandha, theanine, forskohlii, and many more), and a probiotic (this is a complicated one) are where I would start. Rather than buy into something gimmicky, try and optimize health first (a wild idea, I know). I haven’t even touched on liver health but know that your liver is where most of the fat-burning is going to take place. This is a topic for another time, but rerouting your perspective to focus on health, rather than some supplement with lofty promises is a good place to start. If you have readers interested in the biochemistry of it all (hah, jokes), I'll be having an entire blog series going up soon that dives into this type of stuff. 

Now, let’s say the goal is to build muscle - there are, in fact, a few supplements that are useful, all of which are derivatives of food. Protein powders have their role, but not all powders are equal. It’s a bit of a nitpicky point, but I stay away from whey blends or concentrates and stick solely to whey isolates, cold- or micro-filtered whey, and casein hydrolysate. There’s a distinction for each, all of which revolves around their ability to be absorbed. This will be a controversial point given the success of its marketing, but I’d recommend avoiding branched-chain amino acids altogether. It was believed that the branched-chain amino acids (specifically, leucine) were the sole triggers for the mammalian target of rapamycin pathway (mTOR). Think of this as the “muscle-building” pathway in the body. While leucine is essential for this pathway’s functioning, there’s much more to it (as is the case with any of our biology). Essential amino acids (these are the amino acids our bodies cannot synthesize) need to be consumed for the mTOR functioning. Essential amino acid supplements have their place (albeit, a small one), but you’re better off eating whole food.

The marketing campaign for BCAAs points out the major flaw with supplement companies – they cherry-pick data. Whatever the agenda may be, supplement companies will take whatever scientific finding is remotely relevant to their product, pull data out of context, and create a slick marketing campaign. People will continue to fall for this strategy and the supplement companies know it. Fun fact, as of 1994 the FDA has to disprove a supplement company’s claims to have their product removed from store shelves rather than the supplement company having to provide evidence that their product does what’s claimed. The burden is of proof is on the FDA and it can take years (if ever) for them to get around to it. Just remember that tidbit when shopping around. 

On the flip side, are there particular supplements (workout-specific or generally dietary; let's assume that the person in question has a clean bill of health and is looking to build lean muscle) that you think of as "must-haves" or at least generally helpful to take?

I touched on a few things up above but let me state that there are never any “must-haves”. Most would probably be better off spending that money on quality food than some supplement. That being said, when trying to build muscle, it can be quite difficult to get in the amount of food actually needed. I mentioned some various types of protein powders earlier but what I didn’t mention are carbohydrate supplements. When the goal is muscle-gain, carbohydrates should be the biggest variable in the diet. Protein gets maxed out pretty quickly – there seems to be a ceiling effect with it. Dietary fat, while it can increase, doesn’t have nearly as much wiggle room as carbohydrates do. To put it in perspective, carbohydrate intake for the experienced lifter can easily get well over 600 grams per day. That can be a bit of a challenge and that’s where carbohydrate supplements can come in handy. Cyclic dextrin is a favorite of mine to use during the training period – you can read a bunch about it on this blog post of mine:

I’ll actually be taking this blog post down soon and rewriting it as some newer research has come out, but the gist of it holds true. During the training period, a “window of opportunity” is created that increases our body’s ability to partition nutrients.  If the goal is to build muscle, then be sure to take advantage of this window.

Outside of the aforementioned protein powders and cyclic dextrin, the only thing I’d add to the mix would be something to aid in gut health. Digesting all of this food can be difficult, especially to someone who’s new to this whole bodybuilding craziness. A briefly discussed probiotic supplementation – that’s a staple in mine and my client’s arsenals. I can’t stress enough the importance of maintaining gut health. Thing is, it’s a complicated topic.

Here’s some info I wrote about a while back:

I’ll also be taking this one down (I’m in the middle of re-doing the entire blog really) and making it much, much more complete. Along with a probiotic, digestive enzymes and, interestingly, ox bile are excellent gut-health supplements.

There’s a whole host of supplements that can play a role, but I don’t want people to fall into that trap. Supplements should be taken on an as-needed basis which, it turns out, isn’t as-needed as most would think.

Moving on to diet: I'm going to take a bit of time in the article to discuss the classic ol' faithful of a balanced diet vs some of the hot, trendy diets of the moment like keto. On that topic, I tend to be in the camp of thinking that keto is overhyped, and I know from some of your Instagram posts that you neither particularly like or dislike keto.

If you were working with a client whose primary goal was to lose weight and they said they were going to go keto, what might you advise them?

Back when I was working at the clinic, this came up all too often. Now, I’m not for or against keto – I actually don’t care what people do, and in the case of keto, they never stick with it.

When we’re talking about “keto” we’re referring to the production of the ketone bodies, acetoacetate, D-beta-hydroxybutyrate, and acetone. The production of these ketone bodies gets triggered when there are low levels of a certain intermediate of the TCA cycle. The term ketone is not limited solely to this process – there are hundreds of ketones identified. Ketones are merely a classification of an organic compound characterized by a carbonyl group and two different side structures. Ketone bodies are, inherently, acidic compounds. The unregulated build-up of these acids can put a person in a state of ketoacidosis. This state usually involves insulin deficiency/resistance (often called diabetic ketoacidosis) which leads to increased production of ketones in the liver and gluconeogenesis, leading to hyperglycemia and excessive blood ketone levels. This is no trivial point – a “coach” somewhere on the east coast had a diabetic client on the keto diet which ultimately resulted in her death.

The history of the keto diet is actually quite fascinating – it was used as a treatment for epilepsy nearly 100 years ago. But, as is the nature of diet culture, everything gets a weight-loss spin on it. A diet intended for one thing (often for a specific medical condition) somehow gets the weight loss label slapped onto it. So, understanding a diet strategy’s intended purpose is probably a good place to start for anyone about to hop on its bandwagon.

Next, the ultimate determinant for weight loss or gain is energy balance. Diet composition comes after that. That is, if the person is in a caloric deficit there will be weight loss. Note: this is not necessarily the same as that god-awful saying “calories-in vs. calories-out” – that mistakenly oversimplifies the complexity of energy balance. The problem with the keto diet, in this regard, is fat is the primary fuel source. The carbons of a fatty acid are much more reduced than that of a carbohydrate or protein. As such, its potential energy is much greater from its oxidation. This is why a gram of fat is ~9 kcal and a gram of protein and carbohydrates is ~4 kcal. As you can see, it’s a lot easier to consume higher amounts of calories from a fat-rich diet. Provided the person has been coached on portion sizes and educated on a bit of nutrition science, then this can be avoided. As I mentioned before, no one sticks to a keto diet. The longest “long-term” study on the keto diet (with human subjects) has been 26 weeks. This isn’t the fault of the researchers – no one can find subjects who can stay in ketosis longer. It’s simply too difficult of a diet to maintain. As such, the health implications of a high-fat diet for the (actual) long-term aren’t known. I can tell you though that when we’re trying to mimic some human disease state in a mouse or rat model, we typically put them on high-fat diets (around 60%). Take that for what you will. 

In short – if a patient or client wants to go on a keto diet, I wouldn’t stop them – the pushback isn’t something any provider wants to find themselves facing (and often leads to a much worse outcome).

When you're actively training, what type of diet do you tend to adhere to?

Keto, always.


I keep it unbelievably simple. I may not be the best example to follow because of this. I don’t plan on competing ever again, but the dieting habits are still with me. When I have a physique goal in mind (which isn’t too often anymore), I view it as a game of variables. As such, my objective is to control these to the best of my ability – the less there are, the more control I will have over attaining my goal. I mentioned the importance of sleep, stress, and gut health already – diet and training would be the two variables, each of which I know I have great control over.

For my diet, I have 6 meals per day. The number isn’t significant and no, more frequent meals don’t “boost” your metabolism. It simply a pattern than somehow came to be over the years. Protein is kept around 30% of my caloric intake, carbohydrates between 45-60%, and fats make up the remainder. The total caloric intake adjusts depending on the goal and can increase or decrease often – the macronutrient breakdown, however, doesn’t change much. Back when I competed, the last few weeks out from a show were a bit different, but most of the time, it was simply a game of systematically lowering the calories on an as-need basis.

Typically, protein intake is stable throughout the day, the majority of carbohydrates are consumed pre-, intra-, and post-workout, and fats are kept away from the training period. There’s a bit of evidence supporting this structure but nothing too strong – I simply like this pattern and it’s something I know I can keep consistent. And that’s the key – consistency. Consistency is simply concise describing control over variables.

Are there dietary mistakes that you see folks making (such as overindulging on cheat days, misunderstanding dietary macros, or anything along those lines) that may fall through the cracks if someone is taking a "well-rounded/ indulgence in moderation" approach to their diet?

Where to begin? I’d say there are two main classes of mistakes: 1) lack of consistency 2) lack of understanding / misguided application. Lack of consistency predominates – people have a unique ability to always find the path of least resistance. It’s quite fascinating how we come up with excuses. Behavior change theory is something I’m quite fascinated with and, if you comb through the research, every model of behavior change draws a similar conclusion: our conscious effort isn’t the driver of our behavior – our emotions are.

This isn’t limited to dieting. How often is it that you have to do something, say study for a test, but your mind wanders, and you end up procrastinating?  Most of us know what we need to eat, but why is it so difficult to stay consistent? Emotions drive a push and pull between thoughts and feelings which ultimately dictate behavior and thus, your results. This is why, depending on the person, cheat meals can be a terrible idea.

Several years ago, I developed a diabetes prevention program that was built on resolving this very thing. There are 4 main parts to it, all based on behavior change theory:

1) awareness (or maybe more accurately, self-awareness)

2) affective attitudes (this addresses the emotional component)

3) perceived behavioral control (we have to work within the boundaries of what’s realistic for the individual)

4) self-regulating skills (the growth of self-efficacy)

As for lack of understanding, well, that comes with education. It’s an uphill battle given the misinformation that spreads through social media. My advice? Keep it simple. Our body’s chemistry hasn’t changed – stop trying to “biohack” it with whatever fad diet pops up each year.

Finally, I want to cover actual workouts. Since there are enough workout myths to fill an entire book, I want to hone in on what the workout experience is like for beginners.

How would you advise someone who is brand new to lifting to strategize their workouts?

For example, should they focus on doing moderately high rep counts with relatively low weights to start by building stability and muscle control, or are they better off to start by doing assisted machine lifts that target larger muscle groups, or should they start off with the "big three" and go straight for the deadlifts, bench presses, and squats?

I try to get the idea of reps and sets out of a beginner’s mind entirely. In the beginning stages of a fitness goal, these are arbitrary numbers – they simply do not carry meaning yet. Rather, I emphasize the importance of execution. There’s a big difference between moving a weight from point A to point B an arbitrary amount of times and properly executing a movement. As with diet, I’m a proponent of simplicity – getting very strong at basic movements won’t steer you wrong.

When I take on a new client, I spend a great deal of time “re-wiring” their way of thinking about training (which is why beginners are much easier to work with). Terms like “warm-up” and “working” sets carry a slightly different meaning in a bodybuilding context.

As for exercise selection, it can actually take a bit of time to figure out what works best (hell, I’m still trying to figure it out for myself). It’s not uncommon for me to switch things up frequently with a new client for the first few months. We’ll start with a broad plan and refine it until we figure out what’s best for their goal. Machines, free weights, cables, etc. – the “classification” doesn’t matter. What matters is picking a movement that we can progressively load safely, and that has a good strength curve to it. All of this, of course, is determined by their goal.

Let's say that a guy built like me (as in, historically scrawny and generally slow to build muscle) goes to the gym and they feel discouraged when they see younger guys, women, or just other guys their age are out-lifting them and they're starting to feel like it's futile to stick with lifting regularly.

What would you say to him about his self-consciousness or how might you advise him to keep his head up?

Good question – it's certainly an issue and one that probably doesn’t have a clear-cut solution. It’s incredibly difficult to get started as a beginner in the gym, especially if you’re alone. We can get into our own heads, imagining scenarios that make a situation much more daunting than it actually is. Feelings and thoughts play off one another (with feelings probably having a bit more of an impact), but how in the heck do you change what you’re feeling? Earlier I spoke a bit about how emotion is the driver of these. Feelings and emotions are not the same things.

Emotion derives its name from energy in motion – it is a combination of physiologic effects the body experiences under any given circumstance. Feelings are the awareness of emotion. People can have an emotion and not acknowledge them – a concept, I would argue, in which men and women are distinctly different. Knowing that emotion is more physiologically driven, wouldn’t that mean how an individual interprets this (their feelings) is, ultimately, under their control? Let’s take the feeling of stress as an example. What if we shifted our thoughts and beliefs about stress to a more positive one? Because, what is the stress response really? Your stress response serves to build up your stress resilience. How you think and act determines the experience of stress.

So, what if you viewed the stress response as helpful?  The EXACT mechanisms by which stress occurs mirrors the biology of courage. I’d say, don’t suppress the feelings you’re experiencing about a stressful situation – embrace it. Stress in your life isn’t going anywhere, is it? You can absolutely be the architect of your own experience whether it’s the gym or any other anxiety-inducing task. May as well use the gym to strengthen the mind as well as the body, huh?

On a more practical note, having a training partner makes the whole process much easier.

A big thank you to Aaron for chatting with us! If you have any questions, be sure to leave them in the comments below. Also, be sure to follow Aaron on Instagram and check out his website for more great content and insights into your health and wellness.


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