There’s been a lot of hype about the beneficial effects of HMB for athletes looking to add size, reduce body fat, and boost performance.
And as a culture, we’re always looking for newer and better ways to enhance athletic performance and alter body composition.
For the last 20 some odd years, HMB has peaked researchers' curiosity thanks to its anti-catabolic properties, making it a highly useful addition for bodybuilders and athletes looking to maximize muscle gain.
But between piles of human studies and animal studies on its growth-promoting activity, results aren’t entirely conclusive on how effective HMB is for fat loss.
Here’s what we do know.
What is HMB?
HMB is a metabolic by-product of the amino acid leucine. When leucine breaks down in the body, most of it—about 80%—is shunted towards protein synthesis.
The remaining 20% is metabolized into two compounds: alpha-ketoisocaproate (a-KIC) and HMB, with HMB comprising only about 5% of that 1.
And if that’s not enough, leucine is also an essential amino acid, meaning that it can’t be produced in the body and must come from external sources (i.e. diet or amino acid supplements).
So, while leucine is a super effective muscle building supplement that you definitely need, it’s usually not a reliable source of HMB.
The Benefits of HMB For Athletes
The beneficial effects of HMB have been studied for some time, but it hasn’t been until recently that people have really started to use it.
Here are the two most significant benefits to supplementing with HMB:
1. It Reduces Muscle Degradation
Preventing muscle breakdown is one of the major selling factors for HMB.
It’s capable of doing this because of stimulating protein synthesis via the mTOR pathway, or its lengthier name of mammalian target of rapamycin.
The mTOR pathway is primarily controlled by hormones and growth factors, but is also regulated by amino acids and cellular energy status.
In most cells, leucine is the amino acid that activates it. Omitting leucine—an essential amino acid—from the diet causes rapid inactivation of mTOR signaling 2.
That all seems well and good, but what does the mTOR pathway actually do?
It regulates several components involved in protein synthesis, including initiation and elongation factors, as well as the biogenesis of ribosomes themselves.
The process of protein synthesis involves sequential decoding of the mRNA into proteins, which is performed on the ribosome.
In this situation, the ribosome acts as an enzyme to catalyze the formation of the peptide bonds linking amino acids of the new protein 2.
Without the ribosome, proteins cannot form, and muscles cannot grow.
HMB may also play a role in protein synthesis through stimulating expression of IGF-1 and augmenting the growth hormone (GH) response to high-volume resistance exercise 3.
2. It May Help To Balance Your Stress Hormones
Your stress hormones can be a make or break when it comes to fat loss.
In normal amounts, cortisol is beneficial for your body. It’s not only an anti-inflammatory hormone, but it also acts to buffer the effects of insulin, i.e. it enables you to burn body fat for energy while also maintaining stable blood glucose levels.
However, when levels of cortisol are chronically high due to mismanaged stress, problems start to pop up—weight and fat gain being a big one.
That’s because cortisol puts your body into stress mode, which also means your body is going into protection or reserve mode.
It holds onto every ounce of energy it can by slowing down your metabolic rate. So, not only are you not burning calories as efficiently, you’re also increasing susceptibility to insulin resistance.
By nature, cortisol is a catabolic hormone, meaning that it breaks down proteins to supply the body with fuel.
The amino acids released can then be converted into glucose through a process called gluconeogenesis.
The problem with that is when this glucose isn’t used, it collects in your bloodstream and causes high glucose and subsequently high insulin.
When this is happening all the time, your body becomes resistant to circulating insulin, and you now have insulin resistance.
One of the characteristic signs of high cortisol and insulin resistance is weight gain and abdominal fat.
But where HMB comes in is that it may help to blunt the effects of cortisol, especially during periods of fasting, keeping you in an anabolic state, preventing muscle breakdown, and preventing fat storage 4.
The Science Behind HMB and Fat Loss
The mechanisms behind HMBs effects are not well understood, but there is some research to support its efficacy.
While it’s not going to be that magic pill that gets you shredded at the drop of a hat, it may have a more indirect route to helping promote fat loss.
First, through decreasing muscle protein breakdown and increasing synthesis.
Like we mentioned before, HMB works on the mTOR pathway to protect muscle tissue, minimize muscle loss, and boost muscle growth.
Increased muscle mass has been associated with improved glucose metabolism, possibly being explained by insulin and IGF-1’s effect on pathways that promote insulin-stimulated glucose disposal and anabolic growth in muscle 5.
Basically, having more muscle mass won’t inherently help you burn more calories and shed fat—at least not substantial amounts—but it can help you do more work, which will ultimately help your muscle grow and help you burn more fat.
Second, HMB May Improve Fat Oxidation.
There isn’t a lot of evidence available to support the theory that HMB stimulates fatty acid oxidation, but what we do know is that it has a beneficial effect on components of energy metabolism.
This is primarily adenosine monophosphate kinase (AMPK)--a molecule that plays a role in energy homeostasis by activating glucose and fatty acid uptake and oxidation when cellular energy is low.
As a result, you’re not only boosting your energy levels, you’re also burning fat.
As we’ve mentioned, most HMB studies focus on resistance training and muscle growth, so results linking HMB with increased fat loss are sparse and somewhat inconclusive.
However, one specific study looked at the effects of HMB supplementation on body composition and exercise performance of 16 elite male rowers.
Men were given 3g daily of HMB or a placebo for 12 weeks while following their usual training program; groups were switched after a 10-day washout period.
The group supplementing HMB showed improved performance, but interestingly, also showed more significant fat loss than the placebo group; — 0.9kg decrease to a gain of +0.8 kg, respectively 6.
But multiple other studies are showing the opposite effect in trained individuals; HMB supplementation combined with resistance training may improve muscular strength, but has a negligible impact on altering body composition 7, 8.
What is more interesting is that HMB may have a different effect on untrained individuals. One study looked at the use of HMB supplementation on body composition in 70-year-old adults following a resistance training program.
Groups were given either 3g of HMB daily or a placebo for eight weeks while participating in resistance exercises five days a week.
Results showed the group supplementing HMB had greater increases in lean mass and body fat loss compared to the placebo 9.
HMB and Cutting
Cutting is a common thing you hear about regarding physique and bodybuilding shows, as well as things like martial arts where making weight for a fight is non-negotiable.
And while these two events differ quite dramatically, the commonality between the two is their desire to maintain muscle mass and strength, while at the same time dropping their body fat or weight.
The idea behind the cutting process is knocking back your calorie intake and ramping up your energy expenditure to burn fat and weight fast. While it’s not necessarily a ‘healthy’ practice, it gets the job done.
In doing so, it encourages body fat breakdown for energy because calories (and generally carbs) are cut back to the extent that it forces your body to look for alternate energy sources.
But in the process of doing this, you put your body into a catabolic state, whereby that precious muscle you worked so hard to build may be at risk. And even when cutting, you want to maintain your muscle mass.
In scenarios like this, you turn to HMB.
Because of its anti-catabolic properties, HMB can be beneficial for athletes who aren’t interested in losing all of their hard work trying to lose fat.
Based on the available research for HMB and fat loss, there isn’t a ton of evidence to suggest it has a direct role in altering body composition and helping you burn fat.
But what is apparent is that HMB may help to mitigate muscle protein degradation, especially during fasted training, which can significantly help if you’re looking to maximize muscle growth.
Where You Can Find It
HMB is available as a pure supplement, but it seems to be more potent for fat loss when combined with other fat-incinerating ingredients.
Burn Lab Pro is a powerful blend of five unique ingredients—Forskolin, cayenne pepper extract, HMB, GTF chromium, and black pepper extract—designed to increase muscle growth, maximize performance, and shed fat.
These ingredients team up to boost each other’s beneficial activities, leaving you with the cleanest, most powerful and effective fat burner ever developed.
- A Molfino, G Gioia, F Rossi Fanelli, M Muscaritoli. Beta-hydroxy-beta-methylbutyrate supplementation in health and disease: a systematic review of randomized trials. Amino Acids. 2013 Dec; 45(6): 1273-92.
- X Wang, CG Proud. The mTOR pathway in the control of protein synthesis. Physiology (Bethesda). 2006 Oct; 21: 362-9.
- JR Townsend, JR Hoffman, AM Gonzalez, AR Jajtner, CH Boone, et al. Effects of β-Hydroxy-β-methylbutyrate Free Acid Ingestion and Resistance Exercise on the Acute Endocrine Response. Int J Endocrinol. 2015 Feb; 856708.
- G Tinsley, AH Givan, AJ Graybeal, MI Villarreal, AG Cross. β-Hydroxy β-methylbutyrate free acid alters cortisol responses, but not myofibrillar proteolysis, during a 24-h fast. Br J Nutr. 2018 Mar; 119(5): 517-526.
- AC McPherron, T Guo, ND Bond, O Gavrilova. Increasing muscle mass to improve metabolism. Adipocyte. 2013; 2(2): 92-98.
- K Durkalec-Michalski, J Jeszka. The efficacy of a β-hydroxy-β-methylbutyrate supplementation on physical capacity, body composition and biochemical markers in elite rowers: a randomized, double-blind, placebo-controlled crossover study. J Int Soc Sports Nutr. 2015; 12: 31.
- JS Thomson, PE Watson, DS Rowlands. Effects of nine weeks of beta-hydroxy-beta- methylbutyrate supplementation on strength and body composition in resistance trained men. J Strength Cond Res. 2009 May; 23(3): 827-35.
- RB Kreider, M Ferreira, M Wilson, AL Almada. Effects of calcium beta-hydroxy-beta-methylbutyrate (HMB) supplementation during resistance-training on markers of catabolism, body composition and strength. Int J Sports Med. 1999 Nov; 20(8): 503-9.
- MD Vukovich, NB Stubbs, RM Bohlken. Body composition in 70-year-old adults responds to dietary beta-hydroxy-beta-methylbutyrate similarly to that of young adults. J Nutr. 2001 Jul; 131(7): 2049-52.