Is the Testosterone Crisis Real? The Numbers Behind the Headlines | Signal Ep 1

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24:06Dr. Jordan Feigenbaum:Your family will find the perfect vacation in Missouri. Missouri, it's the getaway that gets... All of you. Plan your family fun at visitmo.com. All right, we are back here in the Barbell Medicine Podcast. before the break, we looked at how broken the system around testosterone is right now. A quarter of men start treatment without ever getting their blood tested. Most supplements have no data or are outright contaminated. And the lab test itself, it normalizes on its own about half the time. And now for the second headline. Testosterone levels are declining. Every generation has less testosterone than the one before it.

24:43Dr. Jordan Feigenbaum:There's usually a YouTube thumbnail attached that implies civilization is also ending. Now look, the decline is probably real, but the size of it has been overstated, and the cause of it is a lot less mysterious than the coverage wants it to be. Here's where that headline comes from. It's the Massachusetts Male Aging Study. They followed roughly 1 ,700 men from the Boston area over time. They tested two different birth cohorts. These are groups of men at the same age who were born 15 years apart. The younger cohort had testosterone levels between 15 and 20 % lower than the older one. even after adjusting for health factors, including obesity.

25:18Dr. Jordan Feigenbaum:Studies from Finland and Israel found similar patterns. That's three independent groups, three different countries, each using the same type of test throughout their study. The same finding emerging independently carries some weight. These are studies behind the commonly cited figure, approximately a 1 % year decline in testosterone at the level of the population. A few problems though. Those studies were small, they used older testing methods, and the most recent data they included is nearly 20 years old. So what happens when somebody finally does this at scale with up-to-date data? A 2025 meta-analysis pooled more than 1 ,200 studies with over 1 million subjects spanning from 1971 to 2024.

25:55Dr. Jordan Feigenbaum:The decline they found was approximately 0.56 % per year, half of what the headline normally reads. There's one more finding from that meta-analysis that matters. When they broke the studies down by testing method, the studies using mass spec, the most accurate test available, showed no significant decline at all. The authors attributed this to a shortened surveillance period, only 30 years of mass spec data versus 50 years of data overall. But if the decline were truly around 0.3 % per year, a conservative estimate based on this study, and we have high quality data on more than 100 ,000 subjects across 30 years, which the study did, that should be more than enough to detect the predicted 9 % cumulative drop.

26:36Dr. Jordan Feigenbaum:The most accurate test and the largest available sample found nothing. So the real decline in population testosterone is probably closer to 0.3 to 0.4 % per year, which brings up two questions. Why is the commonly reported number so much higher, and why is testosterone going down in the first place? The commonly cited 1 % per year is a mixture of three things. A modest biological decline, fat that BMI can't measure, being labeled as an unexplained cause, and testing artifacts from comparing two different rulers across eras. Let's walk through each one. First, the test changed. Most testosterone research through the mid-2000s used immunoassays.

27:12Dr. Jordan Feigenbaum:Now, immunoassays don't actually measure testosterone directly. They infer the concentration of testosterone by measuring how much of a labeled decoy molecule gets displaced from an antibody. The problem is that other steroids, like estradiol, a type of estrogen, DHT and DHEA, among others, displace this decoy too. This is called cross-reactivity, and it means that immunoassays systematically overstate testosterone levels, especially at low concentrations. At low levels, the overestimation is large enough to push a genuinely deficient man above the diagnostic threshold. It looks normal on paper when he's really not.

27:47Dr. Jordan Feigenbaum:Now, labs started switching to mass spec in the late 2000s. It identifies testosterone by exact molecular weight. It's more accurate, and it has less noise. When researchers retested stored blood samples from men previously measured by immunoassay, the proportion of those falling below 300 nanograms per deciliter nearly doubled. The older tests had been overstating it. The Endocrine Society responded by revising the lower limit of normal from 300 to 264. The threshold dropped because the test got better, not really because the men got any worse. So across the last 50 years, the older immunoassay values read high and the newer mass spec values read accurately.

28:24Dr. Jordan Feigenbaum:If you compare them side by side, part of the decline is just two different rulers measuring the same thing. So Austin, when you're looking at testosterone research and the study used an immunoassay, how much does that change how you read the result?

28:39Dr. Austin Baraki:I think that this is something that points to just a broader issue in research interpretation when you are a practicing clinician. And the point that I'm getting at is the applicability or the generalizability of a study to the context where you're going to be potentially using or applying the result. Now, I am not an analytical chemist, although having dabbled in a little bit of it in my undergrad studies, and I certainly rely on a lot of laboratory medicine in practice doing and interpreting labs and requires to some extent having an awareness of their limitations and caveats and problems that I run into all the time with labs that I might order in a hospitalized patient or in an outpatient.

29:21Dr. Austin Baraki:How much do I trust this result? There are various things that can make blood sodium level falsely low it can make an a1c falsely high and that's stuff that requires a lot of dedicated deliberate training and experience to be able to interpret and apply accurately and so i will admit you know earlier on in my career not having a great sense of this uh kind of knowledge base around immunoassay versus mass spec as it relates to the reliability of your testosterone levels That's not something that I was very, very in tune with very early on. But since becoming more aware of these things, it has impacted, again, the generalizability of a given piece of research to the patient in front of me.

30:05Dr. Austin Baraki:And it has also made me more attentive to the test that I'm ordering on a patient. So, for example, if now when I'm ordering these tests on folks and they're going to go get it done at a lab, I am somewhat deliberate in either how I order it or once I see the result or wanting to know what type of assay this lab uses. Because, again, there are these limitations. There are the kind of very older analog assays versus some of these immunoassays versus the modern mass spec. and people who have listened to us talk about this or others might've heard of like, this equilibrium dialysis methods and various fancy things that have different pros and cons, both in terms of accuracy and cost and things like that.

30:45Dr. Austin Baraki:So really it's just a matter of like, how applicable is this result that I'm seeing in this research paper to the patient in front of me or their test result? So if I have an older research paper that is run using older immunoassays and yet I'm trying to apply it to a patient in front of me using a mass spec result, I might have to be a bit more cautious. It doesn't mean it's completely useless, but it doesn't mean that I should just mindlessly, you know, apply one data set to a different context without being a bit more critical about it.

31:12Dr. Jordan Feigenbaum:Yeah, I think overall for the listeners at home, it's like when you're considering this decline that we've seen at the population level, and it's been quoted at 1 % per year for 20 years or more, at least half of that is due to the lab tests changing in the data sets that we currently have. when we restrict the analysis to just the quote good lab test the one that's relatively accurate that decline almost disappears it's at least half perhaps less than what's originally stated which kind of brings up the next question well all right look if that's just half of the explained drop what's the proportion what's the cause of the other half and i think that problem is another measurement issue that these studies when they're quote correcting for obesity they're using bmi which unfortunately misses a lot.

32:00Dr. Jordan Feigenbaum:The problem with BMI, and we stated this on this podcast, in many different ways, many different contexts, is that it both systematically underdiagnoses obesity, meaning that it misses a lot of people who are carrying too much body fat, but who do not have a BMI over 30, misses about half of men, for example. And it also doesn't tell you where the fat is. So for example, a person could have too much fat that BMI just period. And that fat could be surrounding their organs called visceral adipose tissue. So all three of these major quote secular decline studies adjusted for obesity using BMI. And as we know, BMI measures body weight relative to height, but it does not distinguish fat from muscle, does not distinguish visceral fat from subcutaneous fat under your skin.

32:47Dr. Jordan Feigenbaum:And that visceral fat is hormonally active. We call this VAT, which stands for visceral adipose tissue. Again, that's fat packed around your organs. And this fat contains the enzyme aromatase, which drives testosterone lower. BMI doesn't correct for that at all. And as we mentioned, since it does misclassify about 50 % of individuals as non-obese, we get come up with that number by comparing BMI to DEXA scanning, which is much more accurate for not only telling you how much body fat the person has, but also where it is. So BMI performs worse also at the lower end of obesity, where many men with excess visceral fat register below 30.

33:27Dr. Jordan Feigenbaum:They might be 28 or 29, might be carrying too much body fat. BMI does pretty poorly there. Now, why this matters is because visceral adipose tissue or VAT, those levels have been going up much faster than BMI over the same time frame that we've seen this apparent decline. Men at a given BMI had measurably larger wastes in 2000 than compared to 1988. Generation X carries significantly more abdominal fat than baby boomers at the same age. Men have been gaining abdominal fat faster than overall weight. The same BMI reading represented more visceral fat in 2010 than it did in 1985. We also see a decline in muscle because grip strength has also declined across birth cohorts in multiple westernized countries after adjusting for height, suggesting that muscle mass is declining and fat mass is increasing at any given weight across the generations.

34:16Dr. Jordan Feigenbaum:So all of this taken together to me suggests that, look, you can't use BMI alone because it's missing visceral adipose tissue. And even if BMI has stayed stable, people are still getting fatter within that same BMI range. So it is insufficient. So the three studies adjusting for obesity using BMI and finding the same residual decline in testosterone levels are all making the same error here. They're calling the decline unexplained because their instrument can't measure the very thing that explains it. So the tests overstated testosterone in older studies and BMI could not see the visceral fat that suppresses it.

34:53Dr. Jordan Feigenbaum:What happens when you fix both problems at once? There's a really elegant study done by Nianti who used archived blood samples from 1988 to 1991. And then a second set of archived blood samples from 1999 to 2004. Right. So spread out by just about a decade. they used the same test in the same laboratory at the same time which removes any possibility that calibration drift of the testing platform contributed to the difference in levels but they also added a waist circumference the venerable waist circumference to alongside bmi to model for obesity now after adjusting for age race bmi waist circumference and lifestyle factors there was no significant decline in total or free testosterone.

35:40Dr. Jordan Feigenbaum:So that corroborates the data from the largest meta-analysis that we have as well, using the best test that is available. When we fix the testing artifact and we measure the body fat properly, this sort of secular decline disappears in a nationally representative sample. So Austin, as a doctor, when you see a study design like that, same lab, same testing platform, and they added waist circumference and the decline suddenly vanishes, what does that tell you?

36:06Dr. Austin Baraki:Yeah, I think you did an excellent job with your homework and analysis here. And I think that the result of this study, really the main effect is going to be to upset people whose preferred narrative is the decline of men or the decline of Western civilization, or here's my supplement stack that will serve to restore your testosterone levels because, you know, men these days aren't what they used to be. that's that's probably the main take-home is people who prefer that narrative explanation might be a little bit upset to find out that maybe it's quite a lot simpler than that uh the tests have gotten better and uh that is a big part of the result vanishing and then the the rest is uh yeah excess visceral body fat that uh is well known and well characterized to have harmful effects on all sorts of things including on this testosterone axis yeah i think that's that's the

36:57Dr. Jordan Feigenbaum:best explanation to me as well. If we consider this sort of like base, you know, assumption that testosterone levels have been going down 1 % per year for 20 years, half of that is due to the testing issue. And the other half, or at least most of the other half is due to the expansion in obesity. The rest, whatever's left over to me is likely noise, you know, and not terribly concerning from a clinical standpoint. That's the way I think about it. And if you really want to blow your own mind. Just go look at testosterone data from the last 10 years, right? So not necessarily 2026. I think the data ends 2023 or 2024, but the last 10 years of testosterone, uh, average level data in the United States actually shows an increase in the United States.

37:41Dr. Jordan Feigenbaum:And so imagine that headline, right? You know, instead of testosterone levels are going down, men aren't what they used to. If instead it said, thanks RFK, testosterone levels are going up, must be the beef tallow. Yeah.

37:56Dr. Austin Baraki:And none of this is to say that, you know, uh, testosterone deficiency is not a potentially real thing that somebody might experience or that they might have that clinical scenario where they actually stand to benefit from treatment, but rather this looks like wholesale population wide, you know, worldwide decline. That is this emergency that we need to search for this, you know, root cause it's like, okay, it's actually a lot less complicated than you're making it out to be. And so by using appropriate testing methods and then accounting for the general trends that we're already observing with respect to obesity and cardiometabolic disease, we can explain a lot of this.

38:32Dr. Austin Baraki:And that also helps us to direct our attention towards the most effective interventions to address this issue to the extent that it is real on a population level. Of course, you know, when you have a single patient sitting in front of you with a particular set of signs and symptoms and lab tests, I'm much less concerned with population-wide trends. I'm just like looking at that person. But to the extent that this, you know, population level claims have caused such hysteria in the media and things like that, then I think that this is a good analysis to, you know, address that.

39:01Dr. Jordan Feigenbaum:So what does all this mean? The decline is probably real at the population level, but it's probably not unexplained. It's in fact pretty obvious that lab testing has contributed and the increase in body fat has also contributed. And whatever's left over is likely too small to detect reliably with any available data set. The higher figures, 1 % per year, testosterone crisis, civilization ending, reflect a mixture of genuine biological decline, fat that BMI has failed to measure, and testing artifacts. The actual rate after accounting for these is probably much lower. Now longitudinal data shows that men who remain lean, active, and free of chronic disease exhibit stability in their testosterone levels.

39:43Dr. Jordan Feigenbaum:It doesn't really drop well into their 70s and 80s, which again, is a counterfactual that most people either have never heard before, or maybe don't believe based on the sort of priming from all of this other stuff. The decline is not necessarily destiny, it's not going to happen automatically, but it does tend to track with metabolic health rather than your birth year. So Austin, when a patient comes in worried that his generation is losing testosterone, and perhaps just wants you to check because of that. How do you frame this? How do you go about this conversation? Yeah.

40:15Dr. Austin Baraki:Fortunately, this is not a situation that I've actually had to deal with where their primary concern when coming in is for the broader generation. But I can see how that could happen to where they've maybe heard this or seen this headline and they get worried and want to check. And so really fundamentally, I'm doing the same sort of general health assessment that I would on anybody else. How are they feeling? How are they functioning? Are they sleeping? Are they exercising? What's their body composition looking like blood pressure blood lipids cardiovascular risk all those sorts of things and then what are their what are their goals and sometimes you know we i do end up getting to points in these conversations where even if things are all looking okay the person is just like adamant and they really just want to get their test done and again i'm to be to be blunt i don't care enough to be like a rigid paternalistic gatekeeper around this information but rather i try to like get the person on board with the idea of like we do tests in a way that should be hopefully informative to what our subsequent steps are going to be.

41:11Dr. Austin Baraki:So let's like role play this scenario out a little bit. Let's say that you do this test and it comes back at this number. What are we gonna do? Let's say it comes back at this number. What are we gonna do? Let's say it comes back at this number. What are we gonna do? And if we end up in a scenario where the answer to all three of those things is the same, sometimes patients are like, eh, okay, I'll skip it, not worth my time. And they kind of come to that realization in real time during the conversation. Other times they still just wanna get it done. Like, okay, fine, it's your health information.

41:37Dr. Austin Baraki:I'm not here to like gatekeep it from you. That doesn't mean that I'm going to like recommend treating, you know, on the back end if it's a solidly normal number or something like that. So that's the way I would have that conversation is assessing like, where is this concern coming from? Maybe gently, if they're open to having the conversation, pushing back a little bit on some probably some inaccurate ideas about, you know, whether that generational decline is so precipitous. And then really just focusing instead of on the generation or the media or the headlines on like them, their health, their goals, their priorities, and how we can best support those.

42:08Dr. Jordan Feigenbaum:Yeah, well said. Again, focusing on the patient rather than like this narrative that's been built. Although again, that narrative is hard to ignore if it's been beaten into you. So to summarize, the secular decline is real, but it's modest, probably about 0.3 to 0.4 % per year, which is mostly explained by rising obesity and testing artifacts, not a mysterious generational collapse.

42:36Dr. Jordan Feigenbaum:So here's what we're left with. A prescribing system where a quarter of men start testosterone without ever confirming that it's low. A supplement market where the majority of products have no supporting data and 1 in 8 muscle building products is contaminated with undisclosed steroids. A lab test where half of the low results normalize on their own. And a headline about declining testosterone that is mostly explained by rising obesity and the fact that we changed how we measured it. The system around testosterone is not serving the people that it's supposed to help. The guys who are genuinely struggling with fatigue, brain fog, with the sex drive that disappeared, with a body that doesn't respond the way it used to, those guys deserve better than a wellness clinic that treats a number without asking what produced it.

43:14Dr. Jordan Feigenbaum:They deserve better than a supplement aisle full of empty promises. And they deserve better than a single blood draw at 3 in the afternoon that becomes a lifelong prescription. That's why we wrote Signal, and that's what this series is all about. Before we close, five things to take with you this week. 1. A single low testosterone level is not a diagnosis. Roughly half of initially low values will normalize on repeat testing. A snapshot isn't a pattern. 2. The supplement market for testosterone is largely unsupported by evidence. 62 % of products have zero published data. 12 % of muscle-building supplements are contaminated with undisclosed steroids that can actually shut down your natural production.

43:52Dr. Jordan Feigenbaum:3. The secular decline in testosterone is real but modest. about 0.3 to 0.4 % per year, after you account for the testing artifacts and the fat that BMI couldn't measure. When you fix both problems, the decline disappears in nationally representative data. Four, the decline tracks with metabolic health, not your birth year. Men who stay lean, active, and free of chronic disease maintain stable testosterone well into their 70s and 80s. Five, if you're concerned about your testosterone, the first step is not a clinic, not a supplement, and not a single blood draw. The first step is understanding how the system actually works, and what real evaluation looks like.

44:28Dr. Jordan Feigenbaum:Next week on the podcast, how testosterone actually works, feedback loop that produces it, what the number on your lab report really means. It's the concept from our book that I think changes how most people think about this hormone and what a real diagnosis of testosterone deficiency requires. Episode two of four in our Signal book launch series. Everything we talked about today and everything that we'll cover over the next three weeks comes from our upcoming book, Signal. It's the complete picture, the history, the physiology, the diagnosis, the lifestyle interventions, and the treatment protocols.

44:56Dr. Jordan Feigenbaum:If this series is useful, the book goes deeper on every topic. Signal's coming soon. Link in the show notes and at barbellmedicine.com. If this episode was useful, leave us a five-star rating and a review. It's the single best thing you can do so we can keep bringing you other this nuance in health and fitness. I'm Dr. Jordan Feigenbaum. That's Dr. Austin Baraki. We'll catch you next week and every week right here on the Barbell Medicine Podcast.

45:25Bye.