Beta-hydroxy-beta-methylbutyrate (HMB) is one of the best-studied bodybuilding supplements in existence, with over 30 human clinical trials published in peer-reviewed scientific journals.
There are a number of benefits attributed to HMB supplementation, including increased strength, lean mass (muscle) and aerobic capacity; as well as decreased body fat, serum cholesterol, blood pressure and post-exercise muscle damage.
HMB is a naturally occurring metabolite of the essential amino acid leucine. It appears to be completely safe and non-toxic at recommended doses (3–6 g/day).
Sounds like a winner! Makes you wonder why it isn’t the Number 1 Supplement in every bodybuilder’s stack.
Then again, maybe there are reasons why it’s not more popular. Let’s take a look at the science behind the hype.
Much of the cheerleading for HMB is from its inventor, Steven Nissen, D.V.M., Ph.D., of Iowa State University. Dr. Nissen holds 6 US patents covering various uses for HMB, and is a founder of Metabolic Technologies Inc. (MTI), which licenses HMB for use in branded products. MTI operates an information site, hmb.org, where you can read about the wonders of HMB.
As shown in numerous studies, taking 3 g of HMB per day while resistance training can add 2 lbs or more to the average bench press per week and double lean body mass gains. Results are generally noticeable in 3-4 weeks and continue while on your training program. And don’t forget to adjust the dose to your specific body weight. 38 mg/kg-body weight is optimal which means a 250 lb person should take about 4.3 g/day for optimal results.
Does this mean that—if you took 3 g HMB/day for a year (52 weeks)—you would add 104 pounds to your average bench press, and gain 20 pounds of lean body mass instead of 10?
Well, noooooo…not quite. The actual research papers tell a less impressive story. For example, one of Dr. Nissen’s published studies shows a net gain of 1.5 kg of lean body mass (lbm) vs. controls (+2.6 kg vs. 1.1 kg) after 7 weeks of HMB supplementation combined with resistance exercise. Thus, it’s fair to say that the HMB supplemented group had “double lean body mass gains.”
But the graph of the measurements clearly indicates that the increase in lbm occurred only in the first half of the study; then declined slightly over subsequent weeks. In other words, HMB supplementation provided an initial “bump” in gains, but no more.
There’s a similar problem with the vaunted “2 lbs or more” added to “the average bench press per week” claim.
It’s true that the supplement group in this study added 15 pounds to their bench over 7 weeks, vs. only 5.4 pounds for the controls.
It’s also true, however, that the HMB group was significantly outperformed by the controls in terms of absolute weight lifted (314 lb vs. 321 lb).
Even though the two groups were matched for average size and lbm, the HMB group was far less proficient than the controls at the beginning of the study (299 lb vs. 315 lb). An alternate explanation, therefore, is that they simply had a greater capacity to respond to the training.
It’s interesting to speculate about what might have happened over a longer period of training and supplementation. Would any differences between the groups still have existed after 3–4 months?
Other studies have shown that HMB supplementation can increase aerobic capacity, reduce markers of exercise-induced muscle damage, and moderately improve cardiovascular risk factors (serum cholesterol and blood pressure). But once again, the benefits appear to be modest, and the short-term nature of these studies can’t tell us much about the results of long-term supplementation.
The hype also doesn’t take the negative research into account. Contrary to Dr. Nissen’s portrayal, a number of studies have found no significant changes in strength, body composition, markers of muscle damage or sports performance with HMB supplementation. Looking closely at these studies reveals an interesting difference, however. The positive studies used either untrained subjects or subjects with varied training experience. In contrast, the negative studies used highly trained athletes.
Perhaps this explains the disparity in results. For example, it’s possible that a) experienced athletes need a larger dose; b) need to take it longer to see results; or c) both.
In my opinion, however, another—and more likely—possibility, is that HMB provides a small, but significant boost for people who are just starting to work out. It’s a different story for people who are adapted to training.
“Real world” experience seems to bear this out. Very few experienced bodybuilders have reported any benefits from HMB supplementation. I certainly didn’t notice any when I tried it, nor did anyone in my immediate circle.
Paul’s comments: I attempted to use HMB… numerous times. The only “result” I experienced was a splitting headache. No matter what brand, not matter what the circumstances… 20 minutes within taking my HMB serving, my head would be pounding.
So what conclusions can we draw about HMB?
HMB certainly seems to have some legitimate therapeutic uses for people suffering from diseases that cause muscle wasting, such as cancer (cachexia) and AIDS. There are a number of studies that show it’s effective—either alone, or in combination with arginine and glutamine (Juven®)—for reducing muscle breakdown and improving nitrogen retention in critically ill patients.
For the rest of us, however, the data is less convincing. HMB appears to offer some modest health benefits and improvements in aerobic capacity. It may also be of some use to people who are just starting a strength training program. At this point, however, there’s little indication that it will produce any significant gains in either lean mass or strength for experienced lifters.
HMB supplements are sold by a number of companies, including EAS, Sci Fit, Primaforce and TwinLab.
In addition, it’s an ingredient in several combination products, such as EAS’ Muscle Armor (which contains Juven® plus taurine) EAS’ BetaGen (HMB with creatine, glutamine and taurine), MHP’s A-Bomb (HMB with branched chain aminos, alpha-ketoglutarate and other aminos) and Beverly International’s Muscle Synergy (HMB with arginine, creatine, citrulline, glycine, and ornithine).