THE EFFECTS OF AN EIGHT WEEK KETOGENIC DIET VS. A CYCLICAL KETOGENIC DIET ON PERFORMANCE AND TESTOSTERONE IN
A RESISTANCE TRAINING PROGRAM
J. LANE Journal of Strength and Conditioning Research 2016 VOLUME 30 | SUPPLEMENT 1 | FEBRUARY | S48
Introduction: Our lab recently examined the effects of the
ketogenic diet (KD) compared to a western diet regarding
strength related performance; additionally, free and total testosterone
was evaluated. Individuals on the KD saw similar
adaptations in strength and similar changes testosterone.
Comparisons of the KD against a cyclic (CKD) in strength,
endurance, and testosterone have not been previously demonstrated
in literature.
Purpose: Therefore the purpose of this
study was to investigate the effects of the KD versus a CKD on
performance and testosterone in resistance-trained males.
Methods: Sixteen resistance trained males participated in
the study (mean 6 SD; age: 23.5 6 3.3; weight: 187.6 6
32.6). Participants on the KD consumed 5% carbohydrate,
25% protein, and 70% fat for 8 weeks. The CKD group applied
the same macronutrient ratio to their diet Monday through Friday,
while altering the ratio on weekends (50% carbohydrate,
25% protein, 25% fat). A periodized resistance training program
was strictly followed 3 days per week throughout the
duration of the study with high intensity interval training implemented
on intermittent days 2 times per week by all participants.
Participants were placed on a 500 kcal deficit derived
from basal metabolic rate determined by the Mifflin St. Jeor
equation. One repetition maximum (1RM) strength was assessed
on deadlift, bench press, and leg press at baseline with
a repeat assessment performed Week 8. Strength endurance
was assessed on the leg press at baseline and re-assessed at
and at Week 8. An ANOVA with repeated-measures was used
to scrutinize the effects of KD and CKD on dependent variables
assuming group (KD and CKD) and time (pre and post) as
fixed factors. The significance level was set at p # 0.05.
Results: There were no differences between groups in the
performance tests or testosterone levels detected at baseline
(p . 0.05). A time effect was observed for bench press and
deadlift 1RM (p , 0.01). There was a trend towards a group by
time interaction (p = 0.07) which favored an increase in the leg
press 1RM in the KD group. There were no significant differences
for leg press strength endurance in both groups. For
free testosterone, there were no group or group 3 time interactions
(p . 0.05). For total testosterone, there was a group 3
time interaction following the diet treatment (p , 0.02). The
pairwise comparisons revealed that only the cyclic group
decreased in total testosterone (10.3%, p , 0.02).
Conclusions: In regards to performance, a strict KD seems to augment
positive strength related adaptations when compared to
a CKD. These responses may be explained by sustained total
testosterone levels seen in the KD group compared to reductions
in total testosterone as a result of the fluctuations in
macronutrient intake.
Practical Applications: Individuals
attempting to optimize adaptations in strength performance
while maintaining testosterone levels should perform a KD
compared to a CKD.
