Key Takeaways

  1. Back in 2014, researchers found that a new variant of HMB supplementation turned this once ineffective muscle building agent into one that was as potent as anabolic steroids.
  2. The idea that an amino acid metabolite could cause people to build 16 pounds of muscle, lose 12 pounds of fat, and increase their squats by 25% in just 12 weeks led many people to question the results. The study, and its legacy, remain controversial to this day.
  3. In the years after the study was published newer research has failed to shed any light on this subject as future studies were either not perfect replications or continued to be suspect.

I’m an optimist.

I’m a secondary researcher, and I’m good at seeing trends among large amounts of data.

After reading more than 20,000 studies while working at Examine, I have a good feel on how many studies are written, and I feel like I can feel an author’s love and excitation through how they write their introductions and conclusions.

I mean, one of my happiest moments was after writing the spirulina page on Examine when a researcher (who researched spirulina for over 50 years) reached out to me and we just giggled like Japanese schoolgirls on just how cool and amazing and so hunky spirulina was. I was so academically giddy!

But I’ve also been pretty good at sniffing out inconsistencies and bullshit.

Every now and then a study comes along that’s very controversial and, at least online, we’re in a culture where “the study trumps all.” You can’t argue with me, I have a citation!

What happens when the citation itself is sketchy? What happens when said citation turns around and spits in the face of all previous research while not even seemingly having two feet to stand upon?

That’s what I’m writing about now.

Today we’re going to be doing a rough review on Wilson et al.’s infamous 2014 HMB free acid study. I’m also going to go over the state of HMB free acid supplements currently.

In case you aren’t familiar with it, this study made waves when it first came out. Why?

Because it showed that the HMB free acid used in the study caused more muscle growth than steroids.

If you’re B.S. detector isn’t blaring yet, it will be in a moment.

Just a note—the full text of the study is free to access online if you want to verify the information yourself.

Hopefully I can lay the seed in your head that “this shit be fucked, yo.”

What Did the Researchers Do?

hmb supplement

The study, overall, was a 12-week resistance training program. Rather than being a standard workout program designed for new lifters, however, the researchers only used people who were considered well trained (by having intermediate to advanced strength levels):

  • 8 weeks nonlinear-periodized resistance training
  • 2 weeks of further training attempting to “overreach” the subjects*
  • 2 weeks of further training but with a tapering of training volume

*Overreaching refers to the initial stages of overtraining, where training capacity exceeds the ability of body and mind to repair itself. Overreaching, however, won’t result in harm if more nutrition or less workload is introduced shortly after to allow recovery.

The experimental group was to take 1 gram of HMB free acid three times a day (3 grams total) with the first dose taken 30 minutes before exercise (in the morning) and the other two at midday and evening meals. On non-training days the three doses were just taken at three different meals.

HMB is a metabolite (breakdown product) of the amino acid leucine. While leucine primarily tells muscles to grow (by increasing protein synthesis), HMB’s role is to prevent muscle protein breakdown. The free acid form (HMB-FA) is absorbed better than the calcium salt form (HMB-ca).

The placebo group had the same dosing schedule, just with a placebo instead of HMB free acid.

Diet was similar between the two groups; a diet of 25% protein, 25% fat, and 50% carbohydrate overseen by a dietitian that started two weeks prior to the study.

You can look at the methodology of the study if you want more information on the specific exercise protocol, follow ups with subjects, and other measurements, but overall it seems to be quite well structured. Everyone followed the supplementation, diet, and exercise regimen closely.

The scientists took a variety of measurements including squat, bench, and deadlift strength, as well as peak power output during a Wingate test (a fancy bicycle), and vertical jump power. They measured body composition with Dual X-Ray Absorptiometry (DXA), too, which is considered extremely accurate.

Ultimately, the researchers gave HMB free acid (3 grams) to one group and placebo to the other. This was paired with a relatively intense workout regimen (at least compared to other studies on workout supplements) in already trained men on controlled diets.

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What Were the Study Results?

The study results section is where we start to see why this study was controversial.

After 12 weeks of supplementation and training, with supplementation being the only differing factor, we found that between the two groups:

Power output increased in the group that took the HMB free acid relative to the group that took placebo on all measurements after 12 weeks.

Here’s what the gains looked like for strength and power:

(The number on the left is for the group that took the HMB free acid, and the number on the right is for the group that took placebo).

Squat: +25.1% vs. +5%

Bench: +11.3% vs. +3.3%

Deadlift: +16.5% vs. +8.2%

Wingate peak power (cycling): +18% vs.+11.7%

Vertical jump power: +20.2% vs. +12%

Body composition improved in the group that took the HMB free acid relative to the group that took placebo on all measurements after 12 weeks.

Here’s what the gains looked like for muscle gain and fat loss:

Lean body mass: +16 pounds vs. +5 pounds

Fat mass: -12 pounds vs. -4 pounds

Quadriceps thickness: +14.3% vs. +4.7%

Reductions in stress, muscle damage, and related negative biomarkers occured in the group that took the HMB free acid relative to the group that took placebo on all measurements after 12 weeks.

Specifically, all of these decreased (which is usually a sign of improved recovery):

  • Cortisol
  • Creatine kinase
  • The 3-methylhistidine:creatinine ratio

Workout volume and strength increased during the overreaching phase in the group that took the HMB free acid relative to the group that took placebo during weeks 8 to 10. In other words, the group taking HMB free acid responded best to the hardest part of the training program, whereas the placebo group was significantly more fatigued.

Now, at the outset this seems like a normal study. Why did it end up being so controversial?

Well, let’s just rephrase some of the results in marketing speak:

  • “HMB supplementation results in 16 pounds of muscle gain in 12 weeks, in people who were already lean and muscular!”
  • “HMB supplementation results in a 12 pounds of fat loss over 12 weeks in already lean and athletic young men!
  • “HMB supplementation results in your squat going up 25% after 12 weeks for people who could already squat 316 pounds!
  • “HMB supplementation results in your deadlift going up 16.5% after 12 weeks for people who could already deadlift 375 pounds!
  • “HMB supplementation results in your bench going up 11.3% after 12 weeks for people who could already bench 247 pounds!

16 pounds of muscle gain over 12 weeks is unheard of for a supplement like this. If you want to counter with “But Kurtis, it was lean mass that contains water” then, sure, but it occurred simultaneously with 12 pounds of fat loss; fat mass isn’t conflated with water weight on DXA.

To show you how ridiculous these numbers are, let’s compare it to the most effective “supplement” for building muscle—steroids.

Studies show that people using steroids and lifting weights will gain around 10 to 16 pounds of muscle over 12 weeks, the same time period used in this study. The average is closer to 10 pounds, which means that in this study, HMB appeared to be more effective than steroids.

The magnitude of these results, given the already strong and lean youth, are outright unprecedented with any dietary supplement. This is in the realm of anabolic steroids.

Wow, the HMB Supplement Is a Holy Grail?

hmb supplement review

The controversy of this study was, in part, due to the obscene magnitude of benefits seen in the HMB supplement group compared to the more realistic benefits seen in the placebo group, but also for a few other reasons.

  • The study was partially funded by Metabolic Technologies Inc. who holds the patent on HMB free acid (the kind of HMB supplement used in this study).
  • Three authors are employed by the aforementioned company and all three were involved in both study design and manuscript preparation.
  • The rationale for these astounding benefits with HMB free acid, relative to HMB calcium salt (the previously used form that’s rather mediocre in most cases) is that it’s absorbed faster.

Honestly, the last point annoys me the most.

Creatine nitrate is potentially absorbed faster than creatine monohydrate and doesn’t make a major difference in effects. Whey isolate absorbs faster than concentrate, doesn’t make an astounding difference in effects. And finally, in this study two of the three doses were taken with meals that generally slows down absorption speed.

To clarify, I know the study was HMB free acid versus placebo but the most common question in response to it was “can I just use HMB calcium salt?” All claims pertaining to improved muscle recovery would apply equally to the two HMB molecules (as they are literally the same) with the only differences being the free acid versus calcium salt debate that seemed to, at the time, be about absorption speed.

Apologies for the conspiratorial thinking.

I’m not normally against industries funding scientific studies (I mean, how is Legion Athletics supposed to give back to the scientific community if we can’t fund anything?) but the combination of funding and patent holding in the context of this study is a major factor in how it became controversial.

The unparalleled magnitude of benefits seen in this controversial study are met with industrial funding by the patent holder and poor reasoning (in my opinion) as to why such a drastic change could occur.

One last bit, and this could get me in hot water so I want to make it clear it’s solely my own belief based on my experiences, but I would advise a bit of caution when it comes to HMB data from any researcher associated with the International Society of Sports Nutrition (ISSN). Several of the authors of this paper are frequently published in the JISSN.

I love the guys at ISSN, I really do, but they just won’t let HMB die an honorable death.

For 30+ years it’s been mediocre (only serving to stall muscle breakdown a bit during periods of fasting, like how we use it in Forge), for 30+ years it has gotten new data confirming it is mediocre, and it always gets new data that does not build up on the body of evidence. Just confirming the same old mediocrity.

I mean, I like replication but only up to a certain point where it serves a purpose.

Keep in mind that I worked at Examine and read well over 20,000 studies over 7 years when I was working there and never have I seen a dead horse being beaten so consistently.

The aforementioned company that funded the study literally just sells HMB supplements and other HMB products! What the hell is this tunnel vision!?

(Note: Uncertain if said company is at all related to ISSN, just pointing out how some areas of sports nutrition are HMB fanatics.)

There is always a point where you get enough null data that you just move onto another topic, or at least change the methodology around a bit, but HMB studies are consistently the same over and over if you look at the past decades.

ISSN isn’t generally a stick-in-the-mud about innovations either, in fact a lot of the latest interesting sports supplement research (like Alpha-GPC, ATP, and phosphatidic acid) comes straight from them!

But man. Somebody there just won’t let HMB supplements go.

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How Does This Compare to Other Research?

does hmb work


This 2014 study was the first major human study on HMB free acid to assess strength and body composition. The same research group preceded this study with one demonstrating the biological efficacy of HMB free acid on muscle protein breakdown (oh look, another Metabolic Technologies product…).

Now that four years have passed we can look at other studies replicating the data.

To begin with, there have been a few studies attempting to expound on the mechanisms as to why HMB free acid could work. Love you guys!

Two studies looked at various immunological markers (to see if the answer lay in inflammation), two looked at potential hormonal explanations acutely, either alone or when it is paired with resistance training.

There is one study published in 2015 that found, yes, HMB free acid is indeed better absorbed than the calcium salt form. Peak concentration in the blood seems to be 76% higher and more seems to be detected in the blood. It’s reasonable to conclude that 1 gram of HMB free acid is “better” than 1 gram of HMB calcium salt if we just want as much in our bodies as we can get.

Undeterred by the controversy, the Wilson et al. research group performed another controversial study in 2016 combining HMB free acid and ATP, which saw a 12.7% increase in lean muscle mass and 25.3% increase in strength over 12 weeks. There were also several academic back and forths published alongside a manuscript clarification.

Seriously, I’m an optimist but those are numbers that should only be seen with rookies or steroid users and not natural lifters already squatting over 300 lbs.

At this point in time Wilson et al. has those two studies indexed in PubMed pertaining to HMB free acid. Both controversial studies, one on HMB free acid alone and the other on HMB free acid paired with ATP.

Personally speaking, it looks like other research groups are trying to make sense of the scraps left behind by the controversial studies. What have they found?

Two studies directly assessed the usage of HMB free acid paired with exercise were short term (so, not fit for comparison to a 12 week study), and one study lasted 6 weeks (still not the best comparison but the best we have right now.)

The six week study, using trained men given the same dose of HMB free acid dosed in the same manner with a similar dietary breakdown (albeit quite different exercise protocol) found:

  • Improvements in the bench press that weren’t significantly different than placebo.
  • Improvements in the vertical jump that weren’t significantly different than placebo.
  • Improvements in the max leg press. 41% versus 25.3%
  • Improvements in the peak power of the vertical jump. 9.5% relative to baseline.

Lo and behold, much more moderate results that are in line with other studies on workout supplements like creatine, Alpha-GPC, and beta-alanine!

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What Does This Mean for You?

Simply put, I don’t know. The research is highly fragmented right now and there are many possible conclusions we can make from the above. The ones I think about the most are:

  1. The two controversial studies were indeed influenced by their funding source in a way that was self-serving. (It’s not a conclusion I want to make but I need to throw it out there since it’s possible given what I’ve shown in this article.)
  2. The 76% increase in peak HMB levels seen with free acid, relative to calcium salt, somehow “flips a switch” that turns this amino acid from borderline useless for anabolism into something that can increase your squat 25% in three months (I feel this is unlikely. Things that have a “switch” like that in the body tend to be discovered sometime in the first 30+ years of heavy research into the topic.)
  3. Building on that… perhaps there is an immunological or hormonal explanation that does not extend to HMB calcium salt (I find this unlikely to explain the entire results since, after all, this was only discovered after the initial study was published and the initial study never mentioned how inflammation and hormones could be a unique variable.)
  4. The specific training protocol used by Wilson et al. that included an overreaching phase was necessary for the results (I believe it’s a factor but don’t think it can explain the magnitude completely. I mean, there were three people who dropped out “due to injury” so it seems to be rather tough training but such large gains in a trained population not taking steroids is not highly believable.)

Ultimately I cannot outright disprove the potential benefits of HMB free acid over the calcium salt form that’s more commonly sold but there are simply too many inconsistencies in the body of evidence and this damn tinfoil hat won’t get off my head.

  • If the magnitude of results is this big then why has only one research group, in the past four years, even attempted replication?
  • Why did the primary research group move on to a combination study (HMB free acid with ATP) rather than replicating their own data?
  • Why is the source of the funding, Metabolic Technologies, only selling HMB and HMB free acid supplements paired with other things (Including ATP and vitamin D3. Wonder if we’re gonna see a study on that in the near future) that correlate perfectly with these one-off studies?

All I can say, for you dear reader, is that if you have money to spare and want an HMB supplement then just be aware that HMB free acid is technically “better” since it is better absorbed but, seriously, don’t expect it to be steroids.

And with that, I take off the tinfoil hat for another day.

What’s your take on HMB supplements? Have anything else to share? Let me know in the comments below!