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The Muscle Building Fat Burning Power Of HMB
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by Edmund R. Burke, Ph.D.
One of the most popular muscle-building supplements to become available in
the last few years is beta-hydroxy
beta-methylbutyrate (HMB). A breakdown
product of the amino acid leucine, studies indicate that it plays a regulatory
role in protein metabolism. After it is produced in the body, HMB meets one of
three fates: 1) it is used in cholesterol synthesis; 2) it is excreted in urine;
or 3) it stimulates protein synthesis in cells and helps maximize the
muscle-building effects of exercise. HMB is considered a dietary supplement
because it is found in some foods, including catfish and certain citrus fruits.
Early human performance studies on HMB conducted at Vanderbilt University in
Nashville, Tenn., and at Iowa State University in Ames found that HMB increased
the strength and lean body mass in athletes.1,2 As both universities
hold patents on HMB and have licensed its production and distribution to several
companies, it should be noted that there was financial interest behind their
studies.
HMB For Men
In a two-part study, Steve Nissen, Ph.D., and colleagues at Iowa State
University randomly assigned 41 male volunteers ages 19 to 29 to one of three
groups. Group one served as a control, taking no HMB and eating from a menu that
contained normal amounts of protein (about 117 g/day). Group two received 1.5
g/day of HMB. Half of this group ate a normal-protein diet, the other half ate a
high-protein diet (175 g/day). Group three received 3 g/day of HMB and was
similarly subdivided into a normal and high-protein diet. All participants
lifted weights for 1.5 hours, three days a week. The study lasted three weeks.
Results showed that HMB improved strength and muscle mass. Subjects gained lean
body mass in a manner responsive to the doses they ingested: 0.88 lbs were
gained in the group receiving no HMB; 1.76 lbs were gained in the group
ingesting 1.5 g HMB; and 2.64 lbs were gained in the group taking 3 g of HMB.
Researchers also found that HMB-supplemented subjects could lift more weight
than unsupplemented subjects. Those subjects receiving HMB were also able to
perform more abdominal exercises. During the three weeks, control subjects
increased performance by 14 percent and supplemented subjects increased
performance by 50 percent. Additionally, total body strength increased 8 percent
in controls, 13 percent in the group taking 1.5 g of HMB and 18.4 percent in the
group taking 3 g of HMB.
These benefits occurred with HMB independent of the level of protein intake.
However, the group consuming the least amount of protein was still ingesting
more than twice the RDA for maintaining nitrogen balance (0.8 g protein per kg
body weight per day). Possibly, a protein intake considered normal by
non-bodybuilding standards would limit the benefits of HMB.
The second part of this study involved 32 male volunteers who participated in an
additional strength-training study. These men were divided into two groups.
Group one received a placebo drink. Group two drank a daily beverage that
contained 3 g of HMB. Protein intake was roughly the same for both groups. All
subjects lifted weights two to three hours a day, six days a week. Subjects
followed this exercise and supplement regimen for seven weeks.
Compared to the placebo group, the HMB subjects developed significantly more
muscle mass. Bench-press strength was almost three times greater in the group
receiving HMB, and strength increases for the squat, although not statistically
significant, were also greater.3
In an attempt to determine the effectiveness of HMB when combined with another
sports supplement, Richard Kreider, Ph.D., and coworkers at the University of
Memphis in Tennessee investigated the effects of 3 g/day of HMB with and without
15.75 g/day of creatine (a supplement important for cellular energy formation).
The study measured strength parameters and body compositional changes in college
football players. The researchers hypothesized that taking both supplements
together could yield a synergistic effect. Their findings, however, suggested
otherwise. Although the trends were positive and paralleled those found in
previous HMB studies, which showed significant improvement, the results from
their study were not statistically significant. Furthermore, creatine did not
augment the benefits of HMB. Although the studies lasted 28 days, the
researchers questioned whether longer supplementation times are needed to show
significant strength gains.4,5
HMB For Women
Does HMB help women and can it improve muscle strength in people who don't
exercise? Another study by Nissen tried to answer both questions by looking at
the effects of HMB on body composition and strength in women who exercised and
those who did not.
In the first part of this study, a group of women engaged in weight training.
Half took 3 g of encapsulated HMB a day for four weeks; the other half took a
placebo capsule. Compared to the placebo group, the HMB-supplemented women
increased their muscle strength by 77 percent, gained twice the lean mass and
lost almost three times as much body fat.
The second part of this study looked at a group of women who did not exercise.
Half the women took 3 g of HMB per day; the other half took a placebo. Neither
group showed significant changes in lean body mass or fat loss. These findings
suggest that HMB plays some key role in muscle-building and fat-burning, but
only in response to exercise.6
An in vitro study by William Cheng, Ph.D., at State University of New York at
Stony Brook, revealed that when muscle cells were exposed to HMB in a test tube,
they burned fat faster. In other words, HMB may help people use fat more
efficiently for fuel, thus both decreasing stored fats and sparing protein and
carbohydrates for muscle building and energy production.7
Although the exact mechanism whereby HMB influences muscle metabolism is not
known, experts offer two hypotheses. The first pertains to the notion that HMB
may be an essential component of the cell membrane. Under stressful situations,
the body may not make enough HMB to satisfy the increased needs of tissues.
Perhaps stress alters enzymes or concentrations of biochemicals that regulate
HMB production. If this is true, dietary supplementation of HMB would help
maximize muscle function.
The second hypothesis revolves around the possibility that HMB regulates enzymes
responsible for muscle-tissue breakdown. This theory is supported by evidence
that HMB supplementation decreased biochemical indicators of muscle breakdown
among weight lifters.8 Additionally, a recent study using isolated
chick and rat muscle indicated that HMB can directly decrease the degradation of
muscle protein.9
Several studies show that HMB is safe and effective for men and women. These
human trials have used up to 4 g/day of HMB for a maximum of four weeks with no
reports of toxicity.10 Current data suggest that HMB supplementation
is safe and beneficial for individuals trying to gain lean body weight and
muscular strength.
John Fuller, director of animal research at Metabolic Technologies Inc., in
Ames, Iowa, is the coauthor of several HMB studies. He reports, "The large
database of animal data along with human studies all indicate that HMB holds
great promise as a tool to maximize muscle function and muscle mass as well as
maximizing health in both animals and humans. HMB appears to have applications
in muscle-wasting diseases in humans and may have applications in slowing the
loss of lean tissue that usually occurs with the aging process."11
Current HMB research is wide ranging. Under study is the biochemical action of
HMB. Clinical trials are also assessing its ability to preserve muscle in
wasting diseases and maintain lean mass in women on weight-reduction diets.
References
1. Abumrad, N. & Flakoll, P. "The efficacy and safety of CaHMB (beta-hydroxy-beta-methylbutyrate)
in humans." Vanderbilt University Medical Center, Annual Report: MTI,
1991.
2. Nissen, S., et al. "Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate
on muscle metabolism during resistance training." J Applied Physiology,
81: 2095-2104, 1996.
3. Ibid.
4. Kreider, R., et al. "Effects of B-HMB supplementation with and without
creatine during training on body composition alterations." FASEB J,
11(3): A374, 1997.
5. Almada, A., et al. "Effects of B-HMB supplementation with and without
creatine during training on strength & sprint capacity." FASEB J,
11(3): A374, 1997.
6. Nissen, S., et al. "Effects of feeding beta-hydroxy beta-methylbutyrate
(HMB) on body composition in women." FASEB J. 11(3): A290, 1997.
7. Cheng, W., et al. "Beta-hydroxy beta-methylbutyrate increases fatty acid
oxidation by muscle cells." FASEB J, 11(3): A381, 1997.
8. Nissen, S., et al., 1996, loc. cit.
9. Passwater, R. & Fuller, J. Building Muscle Mass: Performance and
Health with HMB: 17-18. New Canaan, Conn.: Keats Publishing, 1997.
10. Abumrad, N. & Flakoll, P., loc. cit.
11. Passwater R. & Fuller, J., op. cit., 18-32.
Edmund R. Burke, Ph.D., is an associate
professor of biology at the University of Colorado, Colorado Springs, as well as
the coauthor of Training Nutrition and author of the recently released
book Pyruvate (Keats, 1997). Burke is also director of sports sciences
for the U.S. Cycling Team
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