Effects of a Purported Aromatase and 5 α-Reductase Inhibitor on Hormone Profiles in College-Age Men

Abstract

The purpose of this study was to determine the effects of an alleged aromatase and 5-α reductase inhibitor (AI) on strength, body composition, and hormonal profiles in resistance-trained men. Thirty resistance-trained men were randomly assigned in a double-blind manner to ingest 500 mg of either a placebo (PL) or AI once per day for 8 wk. Participants participated in a 4-d/wk resistance-training program for 8 wk. At Weeks 0, 4, and 8, body composition, 1-repetition-maximum (1RM) bench press and leg press, muscle endurance, anaerobic power, and hormonal profiles were assessed. Statistical analyses used a 2-way ANOVA with repeated measures for all criterion variables (p ≤ .05). Significant Group × Time interaction effects occurred over the 8-wk period for percent body fat (AI: -1.77% ± 1.52%, PL: -0.55% ± 1.72%; p = .048), total testosterone (AI: 0.97 ± 2.67 ng/ml, PL: -2.10 ± 3.75 ng/ml; p = .018), and bioavailable testosterone (AI: 1.32 ± 3.45 ng/ml, PL: -1.69 ± 3.94 ng/ml; p = .049). Significant main effects for time (p ≤ .05) were noted for bench- and leg-press 1RM, lean body mass, and estradiol. No significant changes were detected among groups for Wingate peak or mean power, total body weight, dihydrotestosterone, hemodynamic variables, or clinical safety data (p > .05). The authors concluded that 500 mg of dailyAI supplementation significantly affected percent body fat, total testosterone, and bioavailable testosterone compared with a placebo in a double-blind fashion.

Full text

457
International Journal of Sport Nutrition and Exercise Metabolism, 20, 2010, 457-465
© 2010 Human Kinetics, Inc.
Wilborn, Taylor, Poole, and Foster are with the Dept. of Exercise and
Sport Science, University of Mary Hardin-Baylor, Belton, TX. Wil-
loughby is with the Dept. of Health, Human Performance & Recreation,
Baylor University, Waco, TX. Kreider is with the Dept. of Health and
Kinesiology, Texas A&M University, College Station, TX.
Effects of a Purported Aromatase and 5 α-Reductase Inhibitor
on Hormone Profiles in College-Age Men
Colin Wilborn, Lem Taylor, Chris Poole, Cliffa Foster,
Darryn Willoughby, and Richard Kreider
The purpose of this study was to determine the effects of an alleged aromatase and 5-α reductase inhibitor (AI) on strength,
body composition, and hormonal proles in resistance-trained men. Thirty resistance-trained men were randomly assigned
in a double-blind manner to ingest 500 mg of either a placebo (PL) or AI once per day for 8 wk. Participants participated
in a 4-d/wk resistance-training program for 8 wk. At Weeks 0, 4, and 8, body composition, 1-repetition-maximum (1RM)
bench press and leg press, muscle endurance, anaerobic power, and hormonal proles were assessed. Statistical analyses
used a 2-way ANOVA with repeated measures for all criterion variables (p ≤ .05). Signicant Group × Time interaction
effects occurred over the 8-wk period for percent body fat (AI: –1.77% ± 1.52%, PL: –0.55% ± 1.72%; p = .048), total
testosterone (AI: 0.97 ± 2.67 ng/ml, PL: –2.10 ± 3.75 ng/ml; p = .018), and bioavailable testosterone (AI: 1.32 ± 3.45 ng/ml,
PL: –1.69 ± 3.94 ng/ml; p = .049). Signicant main effects for time (p ≤ .05) were noted for bench- and leg-press 1RM,
lean body mass, and estradiol. No signicant changes were detected among groups for Wingate peak or mean power, total
body weight, dihydrotestosterone, hemodynamic variables, or clinical safety data (p > .05). The authors concluded that
500 mg of daily AI supplementation signicantly affected percent body fat, total testosterone, and bioavailable testosterone
compared with a placebo in a double-blind fashion.
Keywords: fenugreek, anabolic, resistance training
Athletes are continuously searching for ways to enhance
performance, which has directed many to the use of
anabolic steroids. Anabolic steroids are testosterone
derivatives capable of inducing a positive nitrogen bal-
ance and increasing fat-free mass by stimulating protein
synthesis and/or minimizing protein breakdown. Several
studies have shown that administration of testosterone
derivatives to younger (Bhasin et al., 1996) and older
men (Ferrando et al., 2002; Schroeder, Terk, & Sattler,
2003; Snyder et al., 1999), as well as those classied as
hypogonadal (Bhasin et al., 1997; Bhasin et al., 2000),
increases muscle size and strength. This is in contrast
to exercise-induced changes in testosterone that do not
appear to have such a profound effect on muscle protein
synthesis (West et al., 2009).
Testosterone is produced from its cholesterol sub-
strate and almost exclusively binds to the blood proteins
albumin (40%) and sex-hormone-binding globulin (40%).
The remaining portion of testosterone that is not bound
to blood proteins is the active constituent and labeled
free testosterone. Exogenous testosterone can bind to an
androgen receptor and promote intracellular transcrip-
tional and translational events that ultimately increase
fat-free mass (muscle hypertrophy). However, once bound
to its receptor, testosterone can convert to dihydrotestos-
terone (DHT) and estradiol through enzymatic action of
5-α reductase and aromatase, respectively.
Because of the legal and ethical repercussions sur-
rounding anabolic steroid use, nutritional supplement
companies have designed prohormone compounds, or
testosterone precursors, that are marketed to increase
testosterone production similarly to anabolic steroids.
Even though acute sublingual ingestion of androstenediol
was effective in elevating free and total testosterone con-
centrations up to 180 min after intake (Brown, Martini,
Roberts, Vukovich, & King, 2002), this protocol does
not resemble the manner in which the supplement is
purported to work. Other inquiries have established that
prolonged supplementation with prohormone compounds
over the course of weeks to months does not increase
endogenous testosterone levels in conjunction with resis-
tance training (Broeder et al., 2000; Brown et al., 2000;
Brown et al., 1999).
In spite of this, nutritional supplement companies
are continuing to try to develop products that have
ergogenic potential comparable to that of anabolic
steroids. The latest line of nutritional supplements t-
ting this category is aromatase inhibitors (AIs), which
are proposed to suppress estrogen levels and thereby
increase endogenous free testosterone levels (increased
free testosterone:estrogen [Test:Est] ratio), resulting in
increased fat-free mass and strength. It is assumed that

458 Wilborn et al.
these supplements will increase testosterone within
normal physiological levels, but that is not clear at this
point. AIs are not a new classication of drugs; they
have been used as a medicinal preventive and treatment
for breast cancer, and the effects of pharmacologic AIs
such as anastrozole and exemestane on the Test:Est are
well substantiated in both young and old men (Hayes,
Seminara, Decruz, Boepple, & Crowley, 2000; Leder,
Rohrer, Rubin, Gallo, & Longcope, 2004; Mauras et al.,
2003; Taxel et al., 2001). Nevertheless, there are limited
data to support the claims that nutritional companies make
regarding AI supplementation.
Testosterone deciency in males is related to a
considerable decrease in protein synthesis, decreased
strength, decreased fat oxidation, and increased adiposity
(Mauras et al., 1998), which are all regarded as negative
physiological conditions. Elderly men exhibiting a state
of hypogonadism were orally supplemented with the
AI anastrozole for 12 weeks and effectively elevated
bioavailable and total testosterone levels to a normal
range, while estradiol was mildly suppressed (Leder et
al., 2004). Similar results were seen in young, eugonadal
men over the course of 10 days (Mauras et al., 2003),
indicating that AIs have the potential to blunt estrogen
concentrations while concomitantly increasing serum
testosterone levels beyond normal levels.
Nutritional supplements designed with the purpose
of inhibiting aromatase activity are alleged to work
in the same mechanistic manner as AI drugs such as
exemestane. One particular AI supplement (Novadex
XT) increased total and free testosterone by 283% and
625%, respectively, while only slight increases in estro-
gen levels were observed in young, eugonadal men over 8
weeks (Willoughby, Wilborn, Taylor, & Campbell, 2007).
Another investigation using an AI product concluded that
aromatase activity was not completely blocked, even
though increases were detected for free testosterone and
Test:Est (Rohle et al., 2007). These ndings demonstrate
that AI nutritional supplements appear to provide some
possible benets to those interested in increasing their
anabolic status. As noted previously, research is clear that
supraphysiological levels of testosterone are capable of
inducing myobrillar hypertrophy and are vital in the
regulation of muscle mass. It is possible that an herbal
AI could increase testosterone signicantly without
increasing values over normal physiological levels and,
according to recent research (West et al., 2009), may not
be sufcient to induce appreciable change. However, nei-
ther of the previous studies examined the effects of the AI
on performance measures, which are important variables
of interest in athletic and physically active populations. In
addition, no studies to our knowledge have investigated
the performance benets of an over-the-counter 5-α
reductase inhibitor such as saw palmetto or willow bark.
Therefore, it was our purpose to determine the effects of
a commercially available product (Trigonella foenum-
graecum [standardized for Grecunin]) purported to inhibit
aromatase and 5-α reductase activity on strength, body
composition, and hormonal proles in resistance-trained
men during an 8-week resistance-training program.
Methods
Participants
Thirty resistance-trained (>1 year of total-body resistance
training) male participants (placebo [PL] n = 13, 21 ±
3 years, 180 ± 6.4 cm, 84 ± 15 kg, 18.3% ± 6.8% body
fat; AI n = 17, 21 ± 2.8 years, 178 ± 5.8 cm, 85 ± 9.6 kg,
18.8% ± 4.8% body fat) participated in this study. Partici-
pants were not allowed to join this study if they had any
metabolic disorder including known electrolyte abnor-
malities or heart disease, arrhythmias, diabetes, thyroid
disease, or hypogonadism or a history of hypertension,
hepatorenal, musculoskeletal, autoimmune, or neurologic
disease; were taking thyroid, hyperlipidemic, hypogly-
cemic, antihypertensive, or androgenic medications; or
had taken ergogenic levels of nutritional supplements that
may affect muscle mass (e.g., creatine, HMB) or anabolic/
catabolic hormone levels (androstenedione, DHEA, etc.)
within 6 months before the start of the study. Participants
were asked to maintain their normal dietary intake for
the duration of the study and refrain from ingesting any
dietary supplement with potential ergogenic benets.
Those meeting eligibility criteria were informed of the
requirements of the study and signed informed-consent
statements in compliance with the human participant
guidelines of the University of Mary Hardin-Baylor and
the American College of Sports Medicine.
Experimental Design
The study was conducted as a double-blind, placebo-
controlled clinical trial using parallel groups matched
according to total body weight. The independent variable
was the nutritional supplements. Dependent variables
included estimated dietary energy intake; body compo-
sition; upper and lower body one-repetition-maximum
(1RM) strength, upper and lower body muscle endur-
ance (80% of 1RM), anaerobic sprint power, and fasting
clinical blood proles (substrates, electrolytes, muscle
and liver enzymes, red cells, white cells) and anabolic
hormones (total testosterone, bioavailable testosterone,
dihydrotestosterone, estradiol).
Entry and Familiarization Session
Participants believed to meet eligibility criteria were then
invited to attend an entry/familiarization session. During
this session, they signed informed-consent statements and
completed personal and medical histories. Participants
meeting entry criteria were familiarized with the study
protocol via a verbal and written explanation outlining
the study design. This included describing the training
program, familiarizing participants with the tests to be
performed, and having them practice the bench-press and
leg-press strength tests.
Testing Sessions
After the familiarization/practice session, participants
recorded all food and uid intake on dietary record forms

Aromatase and 5 a-Reductase Inhibitor 459
on 4 consecutive days before each experimental testing
session to evaluate nutritional intake. Dietary intake was
assessed using Food Processor nutrition software (ESHA,
Salem, OR). Participants were instructed to refrain from
exercise for 48 hr and fast for 12 hr before baseline testing
(T1). They then reported to the human performance labo-
ratory for body-composition and clinical assessments.
Height was measured using standard anthropometry, and
total body weight was measured using a calibrated elec-
tronic scale (Health o Meter, Electromed Corp., Flint, MI)
with a precision of ±0.02 kg. Heart rate was determined
by Polar (Finland) heart-rate monitor. Blood pressure
was assessed in the supine position after participants had
rested for 5 min, using a mercurial sphygmomanometer
via standard procedures (Adams, 2002).
We then drew ~20 ml of fasting blood using veni-
puncture techniques of an antecubital vein in the fore-
arm according to standard procedures. Blood samples
were shipped to Quest Diagnostics (Dallas, TX) to run
clinical chemistry proles (glucose, total protein, blood
urea nitrogen, creatinine, BUN:creatinine ratio, uric
acid, AST, ALT, CK, LDH, GGT, albumin, globulin,
sodium, chloride, calcium, carbon dioxide, total bili-
rubin, alkaline phosphatase, triglycerides, cholesterol,
HDL, LDL) and whole blood cell counts (including
hemoglobin, hematocrit, red blood cell counts, MCV,
MCH, MCHC, RDW, white blood cell counts, neutro-
phils, lymphocytes, monocytes, eosinophils, basophils).
Blood samples were collected, allowed to sit for 5 min,
and then centrifuged at room temperature. Serum was
extracted, aliquotted into microcentrifuge tubes, and
stored at –20 °C for future analysis. Serum samples were
then assayed in duplicate for free testosterone, total tes-
tosterone (Diagnostics Systems Laboratories, Webster,
TX), DHT, and estradiol (Alpco Diagnostics, Windham,
NH), using enzyme-linked immunoabsorbent assays
(ELISA) and enzyme-immunoabsorbent assays using
a Wallac Victor-1420 microplate reader (Perkin-Elmer
Life Sciences, Boston, MA). The assays were performed
at wavelengths of 450 and 405 nm, respectively, in the
exercise and biochemical nutrition laboratory at Baylor
University.
Participants then had body composition determined
using hydrodensitometry. They reported to the underwater
weighing tank in swimsuits, and body weight was deter-
mined out of water by an electronic scale. Body composi-
tion was analyzed using an Exertech (La Cresent, MN)
body-density-measuring system. The Exertech consists
of a shallow tank (4′ wide × 6′ long × 3′ deep) with a
weighing platform with electronic (load cell) weighing
system connected to a PC. Calibration is conducted daily
by establishing linear interpolation from two known
weights. Data points were recorded with data-acquisition
software from the force transducer. Residual volume was
estimated using standard procedures (Quanjer, 1983).
Participants were submerged in warm water and asked to
exhale a maximal amount of air, after which a signal from
the force transducer produced a readable analog wave.
The most stable waveform was selected, and the mean
value was recorded. Participants performed this procedure
until at least two trials were within a 0.10% difference or
a total of seven trials had been completed. Body density
was calculated after weight was recorded in and out of
water, and the Siri equation was used to calculate percent
body fat (Siri, 1993). Fat-free mass was also calculated
from percent body fat (Siri, 1961).
Participants then performed 1RM lifts on the
isotonic bench press and leg press to assess strength
and then muscle endurance. All strength/exercise tests
were supervised by laboratory assistants experienced
in conducting strength/anaerobic exercise tests using
standard procedures. Participants warmed up (two sets
of 8–10 repetitions at approximately 50% of anticipated
maximum) on the bench press. They then performed
successive 1RM lifts starting at about 70% of anticipated
1RM and increased by 5–10 lb until reaching 1RM.
They then rested for 10 min and performed a muscle-
endurance test at 80% of their 1RM. Participants then
rested for 10 min and warmed up on the 45° leg press
(two sets of 8–10 repetitions at approximately 50% of
anticipated maximum). They then performed succes-
sive 1RM lifts on the leg press starting at about 70%
of anticipated 1RM and increased by 10–25 lb until
reaching 1RM. Participants then rested for 10 min and
performed a muscle-endurance test at 80% of their
1RM. Both 1RM protocols were followed as outlined
by the National Strength and Conditioning Association
(Baechle & Earle, 2008).
After the strength assessments and 15 min of rest,
participants performed a 30-s Wingate anaerobic capacity
test using a Lode computerized cycle ergometer (Gronin-
gen, The Netherlands). Cycle-ergometer measurements
(seat height, seat position, handlebar height, and handle-
bar position) were recorded and kept identical for each
participant across testing sessions to ensure test-to-test
reliability. Before leaving the laboratory, participants
were randomly assigned to a supplement group based on
their body weight and given a training regimen. Partici-
pants repeated all testing after 4 (T2) and 8 (T3) weeks
of training and supplementation.
Supplementation Protocol
Participants were matched into one of two groups accord-
ing to total body weight. They were then randomly
assigned in a double-blind manner to ingest capsules con-
taining 500 mg of placebo (maltodextrin; PL) or 500 mg
of T. foenum-graecum (standardized for Grecunin; AI;
Indus Biotech, India). The doses investigated represent
the current recommended doses sold in nutritional supple-
ments. Participants ingested the assigned capsules once
per day in the morning on nontraining days and before
their workout on training days for 8 weeks. The supple-
ments were prepared in capsule form and packaged in
generic bottles for double-blind administration by Indus
Biotech. Supplementation compliance was monitored
by having research assistants watch participants take the
supplements before supervised workouts and by having
the participants return empty bottles of the supplement at
the end of 4 and 8 weeks of supplementation. Participants

460 Wilborn et al.
reported to a research assistant on a weekly basis through-
out the study to answer a questionnaire regarding side
effects and health status.
Training Protocol
Participants underwent a periodized 4-day/week
resistance-training program, split into two upper and
two lower extremity workouts per week, for a total of 8
weeks. This training regimen has been shown to increase
strength and lean body mass without additive dietary or
supplementary interventions (Kerksick et al., 2009). The
participants performed an upper body resistance-training
program consisting of nine exercises (bench press, lat
pull, shoulder press, seated rows, shoulder shrugs, chest
ies, biceps curl, triceps press-down, and abdominal
curls) twice a week and a seven-exercise lower extremity
program (leg press, back extension, step-ups, leg curls, leg
extension, heel raises, and abdominal crunches) twice a
week. They performed three sets of 10 repetitions with as
much weight as they could lift per set during Weeks 1–4
and three sets of eight repetitions during Weeks 5–8, also
with as much weight as could be lifted per set (typically
60–80% of 1RM). Rest periods between exercises lasted
no longer than 3 min, and rest between sets, no longer than
2 min. Training was conducted at the Mayborn Campus
Center at the University of Mary Hardin-Baylor under
the supervision of trained research assistants, documented
in training logs, and signed off to verify compliance and
monitor progress.
Statistical Analysis
Analysis of variance (ANOVA) for repeated-measures
univariate tests was used to analyze data. Data were
considered statistically signicant when the probability
of Type I error equaled .05 or less. All statistical pro-
cedures were analyzed using SPSS (Statistical Package
for Social Science) version 16.0. All data are reported
as
M
±
SD
.
Results
Medical Monitoring, Dietary Analysis,
and Training Volume
Although a few cases of gastrointestinal discomfort
were reported, no participants experienced any major
clinical side effects related or unrelated to the study.
All participants completed the training protocol without
any complications. No signicant differences (p > .05)
between groups were detected for total daily caloric
intake, macronutrient intake, or training volume.
Hematological Variables
There were no signicant Group × Time interactions (p >
.05) or main effects for time (p > .05) for red blood cell
count, white blood cell count, triglycerides, cholesterol
variables, liver enzymes or proteins, or markers of kidney
function or muscle damage.
Body Composition
Baseline total body weight was not signicantly different
(
p
= .809) between AI and PL groups. A signicant main
effect for time (
p
= .034) was observed for total body
weight for AI (T1= 85.13 ± 9.69 kg, T2 = 85.74 ± 10.59 kg,
T3 = 85.31 ± 10.68 kg) and PL (T1 = 84.02 ± 15.21 kg,
T2 = 85.04 ± 15.73 kg, T3 = 85.63 ± 16.07 kg) groups,
although no between-groups differences (
p
= .083) were
noticed over the 8-week study period. Signicant main
effect for time (
p
= .001) and interaction (
p
= .048) effects
for mean body-fat percentage occurred between AI (T1 =
18.87% ± 4.87%, T2 = 17.91% ± 4.98%, T3 = 17.09%
± 5.04%) and PL (T1 = 18.37% ± 6.85%, T2 = 17.59%
± 7.04%, T3 = 17.82% ± 7.19%) groups (Figure 1). In
addition, a signicant main effect for time (
p
< .001) was
noticed for fat-free mass (AI: T1 = 68.81 ± 6.30 kg, T2
= 70.06 ± 6.57 kg, T3 = 70.40 ± 6.45 kg; PL: T1 = 67.91
± 8.28 kg, T2 = 69.33 ± 8.27 kg, T3 = 69.55 ± 8.06 kg).
Figure 1 — Body-fat changes from baseline testing (T1) through Week 8 (T3), mean Delta ± SD. #Signicant Group × Time
interaction (p < .05). *Signicant main effect for time (p < .05) over baseline at T2 (after 4 weeks) and T3.

Aromatase and 5 a-Reductase Inhibitor 461
Training Adaptations
A signicant main effect for time was detected for AI
and PL groups for bench-press 1RM (p < .001; AI: T1 =
108.55 ± 24.98 kg, T2 = 112.97 ± 24.84 kg, T3 = 114.04
± 23.39 kg; PL: T1 = 95.10 ± 26.89 kg, T2 = 100.17 ±
28.89 kg, T3 = 102.10 ± 29.29 kg) and leg-press 1RM (p <
.001; AI: T1 = 329.15 ± 61.20 kg, T2 = 371.12 ± 68.20 kg,
T3 = 398.53 ± 74.33 kg; PL: T1 = 295.80 ± 71.25 kg,
T2 = 332.17 ± 80.72 kg, T3 = 355.77 ± 81.53 kg) over
the 8-week resistance-training program, despite no
between-groups differences for 1RM tests (Table 1). No
signicant interactions were noted for muscle-endurance
repetitions on the bench press (p = .328) or leg press (p =
.184) or Wingate peak (p = .343) and mean power (p =
.679; Table 2) between AI and PL groups.
Hormones
Significant Group × Time interaction effects were
observed for serum total testosterone (p = .018; AI:
T1 = 14.76 ± 3.97 ng/ml, T2 = 15.38 ± 3.19 ng/ml, T3 =
15.73 ± 3.62 ng/ml; PL: T1 = 15.80 ± 4.91 ng/ml, T2 =
14.38 ± 5.11 ng/ml, T3 = 13.70 ± 3.27 ng/ml; Figure 2)
and bioavailable testosterone (p = .049; AI: T1 = 10.77
± 4.11 ng/ml, T2 = 11.65 ± 3.59 ng/ml, T3 = 12.09 ±
4.16 ng/ml; PL: T1 = 11.80 ± 5.41 ng/ml, T2 = 10.99 ±
5.35 ng/ml, T3 = 10.11 ± 3.29 ng/ml; Figure 3) between
AI and PL groups. No main effect for time was noted for
total or bioavailable testosterone (p > .05). A signicant
main effect for time was noted for estradiol (p < .001;
Figure 4). No signicant interaction effects transpired
over the 8-week study period for free testosterone (p =
.900) or DHT (p = .422; Figure 5).
Discussion
The purpose of this study was to determine the effects
of a commercially available product (T. foenum-graecum
[standardized for Grecunin]) purported to inhibit aro-
matase and 5-α reductase activity on strength, body
composition, and hormonal proles in resistance-trained
men during an 8-week resistance-training program. No
adverse side effects were reported by any of the partici-
pants, nor were any clinical safety markers or hematologi-
cal variables signicantly altered (p > .05), demonstrating
that within the study parameters and the experimental
supplement dosage tested, the product appears safe when
taken over an 8-week time period.
Over the allotted 8-week supplemental time frame,
no changes were seen in any of the hormonal variables
of interest in the PL group. It is noted, however, that the
AI group underwent average increases of 6.57% and
12.26% for total testosterone and bioavailable testoster-
one, respectively (p < .05). Moreover, we did not see a
decrease in serum estradiol and DHT levels, as would be
expected from the AI; instead we observed nonsignicant
increases (p > .05) of 26.62% and 6.10%, respectively.
Even though our results demonstrate that the experi-
mental AI increased endogenous testosterone levels, it
did not completely block aromatase and 5-α reductase
activity. Our results are in concurrence with those of
others (Rohle et al., 2007; Willoughby et al., 2007) who
found marginal increases in estradiol after supplementing
with an aromatase-inhibiting supplement for 8 weeks.
Aromatase inhibits the conversion of testosterone
to estradiol, which subsequently sends feedback to the
hypothalamus and pituitary to promote testosterone
production (Hayes et al., 2000). Therefore, estradiol
levels would likely decrease to see testosterone levels
inversely elevate. Our data agree with this; estradiol
decreased 9.64% from Week 0 to Week 4 before rising
above baseline values by the conclusion of the 8-week
study. Because of a signicant increase in total and bio-
available testosterone without a corresponding increase
in estradiol and DHT, we conclude that the experimental
Table 1 Bench-Press and Leg-Press One-
Repetition-Maximum Values From Baseline
Testing (T1) Through Week 8 (T3), kg
Group and
time point Bench press Leg press
Aromatase and 5-α
reductase inhibitor
T1 108.55 ± 24.98 329.15 ± 61.20
T2 112.97 ± 24.84* 371.12 ± 68.20*
T3 114.04 ± 23.39* 398.53 ± 74.33*
Placebo
T1 95.10 ± 26.89 295.80 ± 71.25
T2 100.17 ± 28.89* 332.17 ± 80.72*
T3 102.10 ± 29.29* 355.77 ± 81.53*
Note. Values are M ± SD. No signicant interactions (p > .05) occurred.
*Signicant difference from baseline.
Table 2 Wingate Power Measures From
Baseline Testing (T1) Through Week 8 (T3), W
Group and
time point Peak power Mean power
Aromatase and 5-α
reductase inhibitor
T1 1,145 ± 185 599 ± 81
T2 1,178 ± 167 606 ± 79
T3 1,178 ± 167 605 ± 91
Placebo
T1 1,311 ± 828 561 ± 76
T2 1,143 ± 182 556 ± 84
T3 1,151 ± 172 572 ± 79
Note. Values are M ± SD. No signicant interactions (p > .05) occurred.

462
Figure 4 — Serum dihydrotestosterone changes from baseline testing (T1) through Week 8 (T), M ± SD. No signicant changes
were noted.
Figure 3 — Serum bioavailable testosterone changes from baseline testing (T1) through Week 8 (T), M ± SD. #Signicant Group
× Time interaction (p < .05).
Figure 2 — Serum total testosterone changes from baseline testing (T1) through Week 8 (T), M ± SD. #Signicant Group × Time
interaction (p < .05).

Aromatase and 5 a-Reductase Inhibitor 463
AI successfully, but incompletely, inhibited aromatase
and 5-α reductase activity.
In the current study, the purported aromatase and
5-α reductase inhibitor had no effect on fat-free mass
but was an effective stimulus for decreasing fat mass
by 1.77%, compared with 0.55% in the PL group (p <
.05). Our data are supported by our previous work (Wil-
loughby et al., 2007), which also found a decrease in fat
mass (3.5%) without changes in fat-free mass during an
8-week resistance-training program in conjunction with
an aromatase-inhibiting supplement.
Increased serum androgen concentrations related to
hypergonadism can accelerate lipolysis via activation of
hormone-sensitive lipase (Hossain & Hornick, 1994),
while a state of hypogonadism is correlated with a dimin-
ished fat-oxidation efciency and a subsequent reduction
in resting energy expenditure (Hayes, 2000). We observed
signicant increases in total and bioavailable testosterone
levels, without any noticeable change in estradiol between
AI and PL, thus indicating a possible connection between
increased androgen levels and decreased fat mass, even
though no markers of lipolysis were assessed.
For the evaluated performance measures, the AI
group increased bench-press and leg-press 1RM strength
8.04% and 21.08%, respectively, but no differences were
seen between groups (
p
> .05), which signies that the
experimental supplement had no effect on overall body
strength. Previous research has shown that supplementa-
tion with anastrozole for 10 weeks did not affect strength,
although total testosterone increased 58% and estradiol
declined 50%. Our previous work (Rohle et al., 2007;
Willoughby et al., 2007) experimenting with aromatase
inhibitors marketed by nutritional supplement companies
did not analyze strength in young, eugonadal men. How-
ever, the effects of testosterone derivatives coupled with
resistance training vastly improve muscle strength across
all populations (Bhasin et al., 1996; Bhasin et al., 1997;
Bhasin et al., 2000; Ferrando et al., 2002; Schroeder et
al., 2003; Snyder et al., 1999). These training adaptations
would appear to be a result of supraphysiological doses of
testosterone, because exercise-induced changes in testos-
terone do not appear to signicantly affect muscle protein
synthesis (West et al., 2009). After its release into the
blood, testosterone can circulate to a desired muscle cell,
translocate and bind to an androgen receptor, and promote
intracellular transcriptional and translational events that
ultimately increase fat-free mass (muscle hypertrophy).
Because muscle cross-sectional area is linearly related to
strength potential (force-production potential; Ratamess,
2008), the effects of supraphysiological doses of testoster-
one derivatives on muscle strength are clearly understood.
AIs marketed by nutritional supplement companies
claim that these products increase androgen levels simi-
larly to anabolic steroids while simultaneously suppress-
ing estrogen levels. The current data, along with those
from our previous work (Willoughby et al., 2007), support
this notion to some extent, because we saw increases in
total and bioavailable testosterone accompanied with
minimal change in DHT and estradiol. Conversely, as
our data suggest, an increase in endogenous testosterone
levels does not always translate to an increase in muscle
hypertrophy and strength. It is likely that the increase in
endogenous testosterone levels from the experimental
supplement did not affect androgen-receptor expression
or the interaction between testosterone and an androgen
receptor, which provides a possible explanation of why
fat-free mass and strength did not increase more than in
the PL group in our investigation. Thus, these data sup-
port the notion that elevated levels of testosterone within
physiological levels have no inuence on muscle strength
in strength-trained young men.
AI drugs have been around for some time and have
successfully been used as medicinal treatments for vari-
ous types of cancer. However, AIs marketed as nutritional
supplements are relatively new to the tness industry,
and there are limited data on their alleged benets as
Figure 5 — Serum estradiol changes from baseline testing (T1) through Week 8 (T), M ± SD. *Signicant linear increase over baseline.

464 Wilborn et al.
advertised by supplement companies. The results of this
study indicate that 8 weeks of supplementation with a
commercially available AI incompletely inhibited aro-
matase and 5-α reductase activity while signicantly
increasing total and bioavailable testosterone levels, as
well as decreasing percent body fat, in conjunction with
a resistance-training program. No changes between Al
and PL were noted for upper and lower body strength,
hematological variables, or clinical safety data.
Acknowledgments
This work was funded by Indus Biotech. We thank all partici-
pants and staff of the human performance laboratory for their
contributions to this work. The results of the current study do
not constitute an endorsement by IJSNEM.
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