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HMB Supplement Review | Big Claims and Flimsy Evidence

HMB Supplement Review | Big Claims and Flimsy Evidence

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I was recently contacted by a well-known strength athlete who receives sponsorship from a nutrition supplement company that specializes in HMB (or β-hydroxy-β-methylbutyrate).

We didn’t actually chat about HMB, but his sponsorship piqued my interest so I decided to research the company and their claims.

Most supplement companies realize that, as an athlete, science is important to you – which is why they often use “science” in their marketing.

They also cash in on the emotion and passion you have for your sport.

They know you want the most out of your training and that you’ll leave no stone unturned to gain a fair advantage.

Unfortunately, most of the time you’re being exploited. I’d like to share with you my experience about this company in hopes that it will make you wiser about the game being played with your passion for sport – and your wallet.

What is HMB?

In brief, HMB is a metabolite of the essential amino acid leucine.

Both leucine and HMB have certain properties which might benefit strength athletes. Specifically as it relates to HMB, it’s been touted to be:

  • anti-catabolic
  • lipolytic
  • able to assist in strength and muscle gain
  • an aid in recovery from exercise

There is some evidence for this, but it’s far from conclusive.

Stretching the Truth 

Part of the problem is that many of the supposed athletic benefits are based on extrapolations and deductions from indirect measures in studies conducted on both animal carcasses and human subjects.

For example, HMB is thought to be metabolized to β-hydroxy-β-methylglutaryl-CoA, which can provide a readily available carbon source for cholesterol synthesis which, in turn, provides precursors for muscle growth.

But is that sufficient to conclude that, if you lift weights and take HMB, you’ll end up with significantly larger muscles than from training alone?

You can see how this is a bit of a stretch.

Just because a substance is involved in certain biochemical pathways related to muscle growth doesn’t automatically mean your strength and size will go through the roof if you take it as a supplement. 

After all, water is an essential nutrient, yet nobody would believe drinking more water before training will increase your power clean by 50 pounds (23 kg).

Misleading claims?

On the company website, they make claims that HMB improves “strength, endurance, and recovery.”

They also claim they’re all about “science instead of hype” and then go on to cite research with their own brief summaries.

From what I could tell, all of these research summaries were positive.

And that’s when I got curious…

The Science

From my previous investigations into HMB, I remembered that the research was equivocal on many training outcomes.  

In other words, some studies showed benefits while others didn’t.

Why then, if this company was so dedicated to science, did they cherry pick studies with positive results?

As a first step, I did a quick search of the scientific literature to refamiliarize myself with the latest findings.

But they’re still not in agreement on whether HMB improves performance.

Before you assume that science is just smoke and mirrors, you must understand that study findings don’t always agree due to differences in research methods.

For example, if you compare men to women, trained athletes vs sedentary couch potatoes, an upper vs lower body exercise, or taking a supplement for seven days vs. seven weeks, you’ll end up with conflicting results.

It is for this very reason that results must be carefully considered and put into context for practical use.

Anyway, my next step was to look at some of the research the company claims to be proof that HMB will increase performance. Here’s an example of one of their cited references.

Company summary
This randomized, double-blind, placebo-controlled study examined HMB supplementation in young male and female elite volleyball players for 7 wks. HMB supplementation resulted in improved body composition and significantly increased strength, while also decreasing fat mass percentage. HMB supplementation also increased peak and mean anaerobic power.  No changes in hormones or inflammatory mediators were seen in this study (Portal et al).

Inconvenient truths

Sounds good, but when I looked at the actual study, a rather different picture emerged. First, the subjects were adolescents, as young as 13.

That’s a huge red flag because there’s an abundance of studies showing that adolescents respond to training and supplements quite differently than adults (i.e., hormonal variations etc).

Besides, can you really compare a 14-year old girl’s physiological response to that of a 36-year old male strength athlete?

Methodological limitations and applications

Next, the researchers used skinfold thickness to determine changes in fat-free mass (i.e., gains/losses in muscle mass).

That method, however, isn’t the most accurate way to measure changes in muscle mass, especially in athletes and young people.

In fact, of the various formulas available, error rates can be as high as nearly 4%.

Consider that the placebo group showed changes ranging between 56.4 kg to 56.3 kg vs. 59.3 kg to 61.6 kg for the HMB group.

Though the experimental group showed statistically significant gains in muscle, in only considering the approximate 4% error rate for the formula, you end up with around 4.5 pounds (~2kg) worth of error.

Since we’re talking about approximate error rates, and not even considering all sources of error for this method, evidence for changes in fat-free mass in this study due to HMB supplementation are pretty flimsy.

But what about strength?

That’s even more interesting. The researchers found that the HMB group significantly increased their strength more than the placebo group, but only in knee flexion (i.e., leg curls). There were no improvements in knee extensions, biceps curls, or triceps extension.

Based on this, how can anyone claim that HMB will make you stronger?

Also consider that strength was measured isokinetically.

This means that equipment was used in which the speed of movement is held constant. In this case, rep speed was measured at 180 and 60 degrees per second.

Of course, any exercise you perform in the gym or competition isn’t isokinetic, it’s dynamic in that the speed of movement changes throughout the range of motion.  

So clearly, it’s difficult to generalize from an isokinetic single-joint leg curl to a multi-joint dynamic squat.

You don’t have to dismiss the science because they used isokinetics to measure strength.

For the purpose of conducting controlled research, it’s necessary that study participants perform the exercises in exactly the same way to minimise error in the experimental protocols.

If any of this upsets you, your complaints should be directed towards the supplement company for misleading claims and promoting false hope.

The research team also looked at peak and average anaerobic power via a cycle ergometer.

Though HMB led to a significantly greater increase in peak and mean anaerobic power (via Wingate test), no significant differences between groups were observed in fatigue, aerobic fitness, or on anabolic, catabolic, and inflammatory biomarkers.

Thus, there does not appear to be any mechanistic explanation for these findings.

In short, you can’t conclude on the back of this study that HMB will increase strength in adults.

The authors of this study discussed the various limitations of their work but the company conveniently left this out of their summary and grossly exaggerated the study findings.

A shady industry

You might want to know the supplement company’s name, but I’m not going to give it.


Because what I shared with you is common in the supplement industry.

This particular company isn’t any worse than the rest and their name is irrelevant.

The point is, you can’t trust them, even if they throw around words like “science” and “clinically proven.”

Even if the company employs scientists, that’s no guarantee either.

Last year, I shined the spotlight how on a company that produces mouthpieces with claims it could increase strength actually misrepresented what their scientists said.

Are these companies purposely lying to you?

I can’t say for certain, but there is no question that they purposely hype their products to drive sales.

Take home message

My personal opinion is that you’d get more out of your training by focusing on maintaining a scientific approach instead of relying on supplements with a flimsy evidence base. 

A recent meta analysis concluded that improvements from HMB in trained athletes were trivial.

Here’s the bottom line: train your muscles but don’t forget to train your brain.

When it comes to supplements, critical thinking and a healthy dose of skepticism go a long way in keeping you from wasting your time and money.


  1. Nissen, S., et al. Effect of leucine metabolite β-hydroxy-β-methylbutyrate on muscle metabolism during resistance-exercise training. Journal of Applied Physiology 81:2095-2104, 1996. (view abstract)
  2. Portal S., et al. The effect of HMB supplementation on body composition, fitness, hormonal and inflammatory mediators in elite adolescent volleyball players: a prospective randomized, double-blind, placebo-controlled study. European Journal of Applied Physiology. 111(9):2261-2269, 2011. (view abstract)
  3. Rowlands, D.S. and J.S. Thomson. Effects of β-hydroxy-β-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis. Journal of Strength and Conditioning Research.  23(3):836-846, 2009. (view abstract)
  4. Slater, G.J. and D. Jenkins. β-hydroxy-β-methylbutyrate supplementation and the promotion of muscle growth and strength. Sports Medicine.  30:105-116, 2000. (view abstract)

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Big Boy

Saturday 29th of October 2022

Your Crazy HMB works I'm taking it

Trebor Lloyd

Tuesday 6th of September 2022

However gains in non-trained persons were small but clear and worthy of further study.