The #1 Marker of Physical Supremacy

And it's free to measure...

We are in an age where people are obsessed with tracking their health.

This is particularly common in high performing, type A men.

So they will obsess over their Whoop scores, HRV, biological age, yet they have 1 marker staring at them in the mirror that they completely ignore because they prefer to find comfort in the data that supports their bias that they are healthy.

You also have a large uptick in men who are getting blood testing done. They are measuring their free testosterone, hormonal profile, while the biggest marker of testosterone (their physique and how they look), is something that they can gauge for FREE.

Now if you have the means to afford these gadgets, tools and diagnostics, by all means, go ahead…

But as mentioned, there is a free, very accurate marker that you can check in a 2 second look in the mirror, and that is your bodyfat percentage.

This is always the #1 thing I will address with my clients, and this article is going to give you the 4 biggest reasons why…

1- Testosterone Maxxing

Whenever I onboard a client and they are concerned about their testosterone levels, whether that’s through blood testing results, the fact they are getting into their 40’s or just some subjective signs: tiredness, erectile dysfunction etc… The first thing I will look at is their bodyfat percentage.

Fat converts testosterone into estrogen, so the more adipose tissue you have on your frame, the higher probability of the sacred testosterone compound in your body that gets converted.

And this is often the advice I give way before thinking about TRT, peptides or any of the commonly rushed solutions we see in the market.

The leaner you are, the better optimized your testosterone levels are, and this is a positive feedback loop of: being lean → lower estrogen → higher testosterone → easier to preserve & build muscle mass

And that beautiful cycle repeats.

2- Insulin Sensitivity

Being insulin sensitive is one of the most powerful markers of metabolic health because it means your body can efficiently shuttle glucose into the muscle tissue where it belongs, rather than leaving it circulating in the bloodstream and storing it as body fat.

Put simply: the more insulin sensitive you are, the better your body handles food, recovers from training, and partitions nutrients toward muscle instead of fat.

This is why body fat percentage matters so much. As body fat climbs, especially around the abdomen, insulin sensitivity generally declines, which means your body has to produce more insulin just to manage the same amount of carbs.

That’s where the problems start: worse energy, poorer nutrient partitioning, harder fat loss, and a much greater likelihood of storing incoming calories as fat rather than using them to fuel performance and build lean tissue.

From a performance standpoint, insulin sensitivity is an elite trait. It allows you to eat more strategically, recover better from hard training, and stay anabolic without constantly fighting your own physiology. This is why the leaner, more muscular athlete usually looks and performs better: they’re not just leaner visually, they’re operating with a better metabolic setup.

This is the exact reason why with each of my clients we will choose 1 quarter a year to do a ‘fight camp’ style shred to maintain & maximise insulin sensitivity and peel away any body fat (particularly if they are above the lethal standards we have developed).

3- Movement Efficiency & Kinaesthetic Skill Acquisition

The biggest mistake I made in my professional athletic career was pack on unnecessary size and bodyfat in order to improve my athletic output.

I remember vividly how much slower I moved, that I would gas out quickly and that with every pound of bodyweight added to my frame, it had huge detriments to my agility, gas tank & ability to perform.

Now this example is obviously at the highest levels of performance, but unnecessary bodyfat on your frame, particularly if you are someone who is running, sprinting, playing sports, will place significantly more strain & stress on your joints, ligaments & tendons.

It’s no coincidence that those who are overweight are far more likely to be prone to total hip and knee replacements, from the sheer stress that is placed on these areas of the body, compounded over decades.

This is also exactly why training standards such as the pull up are baked into the lethal standards criteria, because the heavier you are (and higher bodyfat you have), the harder a pull up is going to be.

It’s also why for squatting, deadlift and pressing patterns, we don’t calculate total weight lifted, we look at it as a multiple of your bodyweight.

4- Heart Health Risk Factors

It’s no secret that heart disease is the #1 leading cause of death in the United States.

And the connection to body fat is not subtle. As body fat climbs, particularly visceral fat stored around the abdomen, you get a cascade of downstream effects: elevated ApoB (the primary driver of arterial plaque), higher LDL particle count, rising triglycerides, lower HDL, and increasing blood pressure. Each of these independently raises your cardiovascular risk. Combined, they stack.

The mechanism is straightforward. Excess body fat drives insulin resistance, which forces the liver to overproduce VLDL particles, flooding the bloodstream with more ApoB-carrying lipoproteins. More particles in circulation means more opportunity for them to embed in arterial walls and begin the process of atherosclerosis. Over decades, that process is what kills people.

The leaner you are, the cleaner your lipid profile tends to be. Not because weight is the only variable, but because low body fat is a reliable signal that your metabolism is running efficiently and not generating the hormonal and inflammatory environment that accelerates heart disease.

This is why body fat percentage sits at the top of the diagnostic hierarchy. Before you start worrying about which supplement stack to run or what your latest blood panel says, ask yourself the simpler question first: are you actually lean? Because the data consistently shows that people who maintain a low, healthy body fat percentage across their lifetime dramatically reduce their cardiovascular risk profile, without needing a single pharmaceutical intervention to do it.

So Before You Start Looking at TRT, Peptides, Supplements & Blood Testing…

Focus on your body fat percentages. It’s the lowest hanging fruit, which if addressed, leads to a cascade of incredibly beneficial changes to your body, hormonal profile and physiology.

It’s no coincidence that it is something that we cover in detail in the lethal physique protocol which is coming very very soon.

It will be a streamlined protocol and something that you all have waited very patiently for instead of piecing together all of the substack articles that have been written.

Until next time.

Jack Krucial