HMB, or beta-hydroxy-beta-methylbutyrate, is a supplement that has intrigued bodybuilders for decades, and may hold specific benefits for those trying to add muscle or maintain muscle while dieting. In addition, the specific actions of HMB have led to some speculation that it might lead to muscle growth even without working out.
Is that possible? Could HMB really add muscle to your frame even without the stimulus of weight training?
While the answers may not be fully understood, science can provide some important clues.
What Is HMB and What Does It Do?
HMB is a metabolite of the branched-chain amino acid leucine, which has been shown in several studies to both increase muscle synthesis and decrease proteolysis — muscle breakdown. It appears from the most recent research that most or all of leucine’s anti-catabolic abilities — its tendency to reduce proteolysis — are due to the production of HMB as leucine is burned for fuel or protein production.
Individual studies of HMB on its own support the notion that it can be a powerful proteolysis inhibitor, but they also suggest the HMB boosts protein synthesis. Under the right conditions — proper training, diet, and rest — HMB can therefore improve your nitrogen balance, which is an indicator of net muscle mass changes in your body.
A positive nitrogen balance generally indicates you’re adding muscle, while a negative nitrogen balance points toward muscle loss.
Can HMB Build Muscle Without Training?
Because HMB can affect both sides of the nitrogen-balance equation, it has the potential to build muscle under a variety of circumstances. Whether you work out or not, your body is constantly creating and destroying muscle cells, so HMB should be able to help you tilt toward a positive balance no matter what your circumstances.
In fact, a 2000 review of available literature point to HMB as an agent for muscle mass gains in young, weight-trained adults AND for muscle mass maintenance and maybe even gains in certain populations of cancer patients.
The truth is, though, that most of the studies available, like this one conducted in 2014 from researchers at the University of Tampa, have focused on the combination of HMB supplementation with weight training. In this particular case, scientists found that HMB boosted recovery and allowed lifters to train more intensely and more frequently than those using a placebo.
So, at this point, there is little available evidence that HMB can build muscle without training, and it’s likely that it would become a controlled substance and not available as a suppliement if this were ever proven. One trend that several researchers HAVE noticed is that subjects without previous training experience tend to gain better than those with long lifting histories.
Much of this difference is likely due to the novel stimulus of weight lifting for untrained individuals, though, and not necessarily to the use of HMB itself.
Should You Use HMB?
There is enough evidence supporting the efficacy of HMB for most lifters to at least consider adding it to their arsenals. It won’t turn you into a championship bodybuilder overnight, but it probably CAN help with muscle growth and recovery if you are training hard and consistently.
Talk to your doctor before using HMB or any other supplement to make sure it won’t cause you any ill-effects. If you get the all-clear, HMB just might get you an edge in building the body you want, but don’t expect it to work if you don’t!
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