HMB, which is short for β-hydroxy-β-methylbutyrate, may be a lesser-known substance as far as dietary supplements go, but it’s been gaining more attention in recent years due to the growing body of evidence that it may help to improve your overall health and appearance in multiple ways.  

That’s why in this article, we’re going over 4 science-backed HMB benefits to give you a better understanding of what exactly you can expect to gain from adding an HMB supplement into your dietary routine. But before we dive too deep into the benefits, let’s talk a little bit more about what HMB actually is, where it comes from, and what it does.  

What is HMB?

HMB is a naturally occurring substance and a metabolite of the important branched-chain amino acid leucine — leucine is one of the 9 essential amino acids and it plays a central role in the maintenance of your body’s muscle tissues (amongst other things).(1)

Some of the leucine that comes in through your daily diet is ultimately converted by the body into HMB, although it’s a pretty minuscule amount.  While relatively small quantities can be obtained through food sources, higher amounts can also be obtained from dietary supplements.

Though they may share some commonalities in terms of their functions, HMB and leucine play separate and distinct roles within the human body. 

Research shows that HMB has both anti-inflammatory and antioxidant properties, helping to both decrease proteolysis (the breakdown of muscle proteins by enzymes) and stimulate muscle protein synthesis — the main biological process through which the body repairs and replaces damaged muscle tissues.(2)

HMB Benefits

Research findings suggest that in combination with diet and exercise, regularly taking an HMB supplement may offer several benefits to your overall health and appearance.  

Trials involving both healthy individuals, and those with certain conditions that affect the health and function of their muscles, have continued to demonstrate the beneficial effects of HMB on the muscle and strength-building processes.(3)

In addition, other research has also demonstrated that HMB may help to enhance recovery, promote fat loss, and improve your body composition to a greater degree than diet and exercise alone.  

Benefit #1: HMB Can Increase Muscle Growth and Strength Gains

The first HMB benefit is that it can help to promote muscle growth.  As we’ve already mentioned, HMB plays an important role in stimulating the biological process known as muscle protein synthesis (MPS), which is the main mechanism through which your muscles actually grow — the higher your levels of MPS, the greater your muscle-building potential.  

More specifically, HMB has been shown to increase MPS through the activation of the mTOR signaling pathway, which helps to coordinate the delivery of fresh nutrients like amino acids and oxygen to your muscles.(4)(5)(6)

Research involving HMB supplementation has demonstrated that it can help to improve the muscle-building process in everyone from healthy young athletes to older frail individuals having issues with muscle wasting.(7)(8)

⫸HMB Supplementation in Healthy People

A number of studies involving healthy adults have concluded that over time, those who supplemented with HMB, on average, saw significantly greater increases in size and strength compared to those who did not.(9)(10)

For example, one study involving healthy participants with previous weight training experience compared the effects of HMB to a placebo.(11) After 12 weeks of supplementation, the researchers ultimately found that those who were given a daily dose of HMB, on average,  saw significantly greater increases in lead muscle mass compared to those who were not (7.4 kg vs 2.1 kg respectively).  

Furthermore, the researchers also observed that those who were given HMB also made significantly greater gains in strength, on average, adding 55 more kgs to their squat, bench, and deadlift totals in comparison to subjects who received only a placebo.

HMB, Frailty and Muscle Wasting

Clinical trials involving HMB have also come to similar conclusions, with most studies finding that regular supplementation (in addition to exercise) can help to improve mobility recovery in frail patients, as well as those with muscle wasting disorders.(12)

For instance, studies involving everyone from frail people recovering from hip fractures and orthopedic surgery to those with non-cystic fibrosis bronchiectasis have demonstrated that those who were given a daily dose of HMB saw significantly greater improvements in the size and strength of their muscles.(13)(14)(15)

Benefit #2: HMB Can Help With Recovery

Not only does HMB help to promote muscle protein synthesis, research shows that it also aids in the prevention of muscle protein breakdown (MPB).  

MPB is a metabolic process that occurs during and after you exercise.   Intense physical activity can cause lots of microscopic damage to your muscle tissues, breaking down some of the structural proteins that make them up. 

These proteins, in turn, must ultimately be replaced in order to maintain the strength and function of your muscles.  Unfortunately, though, it’s a process that takes time, and it’s ultimately one of the main reasons a serious workout can take days to fully recover from.  

However, HMB has been shown to improve recovery time by altering your muscle metabolism.  More specifically, it’s been shown to decrease the body’s production of enzymes like lactate dehydrogenase, which plays a primary role in triggering MPB.(16)(17)

In simple terms, less muscle protein breakdown ultimately equates to less recovery time — if an intense workout doesn’t do as much damage to your muscle tissues, it won’t take your body as much time to make repairs.

benefits of hmb

Benefit #3: HMB Can Prevent Muscle Loss

Because it’s been shown to both promote MPS and decrease MPB, HMB can also help to prevent muscle loss, which is an issue that many people may ultimately face as they become older.  

While muscle protein breakdown is a naturally occurring process, if more protein is being broken down than replaced — aka you have a negative protein balance — it ultimately leads to muscle loss over time.  

The main issue is that by the time that most people enter into their 30s they already have a negative protein balance, which can result in as much as a 5% decrease in lean muscle mass over the course of a decade.  So while 5% may not seem like a whole lot to you, by the time you reach your seventies, those losses can really add up, impacting both your strength and mobility.

Research involving aging populations, however, has demonstrated that regularly supplementing with HMB can help to prevent and even reverse age-related muscle loss.(18)

For example, one study published in the International Journal of Nutrition examined the effects of HMB supplementation on 70-year-old men and women undergoing a 5 day a week resistance training program(19)

After the conclusion of the study, the researchers ultimately found that not only did those who were given HMB not lose any lean muscle mass, they actually saw significant increases, gaining almost 1kg of lean mass over the course of the 8-week trial, compared to the placebo group who lost almost half of a kilogram on average.   

Benefit #4: HMB Can Help Improve Your Body Composition During Weight Loss

The benefits of HMB also extend to the realm of weight loss and body recomposition.  The risk of losing lean muscle mass increases during a hypocaloric diet, when, you’re taking in fewer calories than your body actually needs.  In this state, your body is just as happy cannibalizing lean muscle as it is fat.

The issue is that when most people say they want to lose weight, what they really mean is they want to lose fat, not lean muscle — nobody wants to look skinny fat when they’re done losing weight; they want to look lean and fit by the time they reach their target weight.  

Because HMB can help to both promote MPS and decrease MPB, it can help to preserve more lean muscle mass during a weight cut, helping to more exclusively target fat. 

In fact, several studies have demonstrated that HMB supplementation leads to more fat loss and greater improvements in overall body composition in comparison to diet and exercise alone.(20)(21)

Are There Any Safety Concerns With HMB?

To date, no potential adverse effects have been associated with HMB supplementation in human-based trials involving up to 6 grams of HMB per day.  

In animal studies, no adverse effects have been observed even at extremely high dosages — we’re talking the equivalent of 450g a day for a 200-pound man — which suggests that HMB is likely safe when used appropriately.(22)

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Wrap Up

HMB is a naturally occurring amino acid metabolite that’s been growing in popularity as a supplement in recent years due to the growing body of evidence that can offer several benefits to your overall health and appearance.

On top of helping to improve your muscle-building potential, HMB has also been shown to decrease muscle protein breakdown and muscle loss, which can be beneficial for everything from athletes and aging folks, to those looking to lose weight and improve their body composition.  

While research is still underway, HMB appears to be safe when taken appropriately and no adverse outcomes have been reported in any of the human-based trials that have been conducted up until this point in time.