Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males

TLDR: The results suggest that an intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.

Abstract: Intermittent fasting (IF) is an increasingly popular dietary approach used for weight loss and overall health. While there is an increasing body of evidence demonstrating beneficial effects of IF on blood lipids and other health outcomes in the overweight and obese, limited data are available about the effect of IF in athletes. Thus, the present study sought to investigate the effects of a modified IF protocol (i.e. time-restricted feeding) during resistance training in healthy resistance-trained males. Thirty-four resistance-trained males were randomly assigned to time-restricted feeding (TRF) or normal diet group (ND). TRF subjects consumed 100 % of their energy needs in an 8-h period of time each day, with their caloric intake divided into three meals consumed at 1 p.m., 4 p.m., and 8 p.m. The remaining 16 h per 24-h period made up the fasting period. Subjects in the ND group consumed 100 % of their energy needs divided into three meals consumed at 8 a.m., 1 p.m., and 8 p.m. Groups were matched for kilocalories consumed and macronutrient distribution (TRF 2826 ± 412.3 kcal/day, carbohydrates 53.2 ± 1.4 %, fat 24.7 ± 3.1 %, protein 22.1 ± 2.6 %, ND 3007 ± 444.7 kcal/day, carbohydrates 54.7 ± 2.2 %, fat 23.9 ± 3.5 %, protein 21.4 ± 1.8). Subjects were tested before and after 8 weeks of the assigned diet and standardized resistance training program. Fat mass and fat-free mass were assessed by dual-energy x-ray absorptiometry and muscle area of the thigh and arm were measured using an anthropometric system. Total and free testosterone, insulin-like growth factor 1, blood glucose, insulin, adiponectin, leptin, triiodothyronine, thyroid stimulating hormone, interleukin-6, interleukin-1β, tumor necrosis factor α, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides were measured. Bench press and leg press maximal strength, resting energy expenditure, and respiratory ratio were also tested. After 8 weeks, the 2 Way ANOVA (Time * Diet interaction) showed a decrease in fat mass in TRF compared to ND (p = 0.0448), while fat-free mass, muscle area of the arm and thigh, and maximal strength were maintained in both groups. Testosterone and insulin-like growth factor 1 decreased significantly in TRF, with no changes in ND (p = 0.0476; p = 0.0397). Adiponectin increased (p = 0.0000) in TRF while total leptin decreased (p = 0.0001), although not when adjusted for fat mass. Triiodothyronine decreased in TRF, but no significant changes were detected in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides. Resting energy expenditure was unchanged, but a significant decrease in respiratory ratio was observed in the TRF group. Our results suggest that an intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.

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Original Citation:
Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal
strength, body composition, inflammation, and cardiovascular risk factors in resistance-
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10.1186/s12967-016-1044-0
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Moro
et al. J Transl Med (2016) 14:290
DOI 10.1186/s12967-016-1044-0
RESEARCH
Eects ofeight weeks oftime-restricted
feeding (16/8) onbasal metabolism,
maximal strength, body composition,
inammation, andcardiovascular risk factors
inresistance-trained males
Tatiana Moro
1
, Grant Tinsley
2
, Antonino Bianco
3
, Giuseppe Marcolin
1
, Quirico Francesco Pacelli
1
,
Giuseppe Battaglia
3
, Antonio Palma
3
, Paulo Gentil
5
, Marco Neri
4
and Antonio Paoli
1*
Abstract
Background: Intermittent fasting (IF) is an increasingly popular dietary approach used for weight loss and overall
health. While there is an increasing body of evidence demonstrating beneficial effects of IF on blood lipids and other
health outcomes in the overweight and obese, limited data are available about the effect of IF in athletes. Thus, the
present study sought to investigate the effects of a modified IF protocol (i.e. time-restricted feeding) during resistance
training in healthy resistance-trained males.
Methods: Thirty-four resistance-trained males were randomly assigned to time-restricted feeding (TRF) or normal
diet group (ND). TRF subjects consumed 100 % of their energy needs in an 8-h period of time each day, with their
caloric intake divided into three meals consumed at 1 p.m., 4 p.m., and 8 p.m. The remaining 16 h per 24-h period
made up the fasting period. Subjects in the ND group consumed 100 % of their energy needs divided into three
meals consumed at 8 a.m., 1 p.m., and 8 p.m. Groups were matched for kilocalories consumed and macronutri-
ent distribution (TRF 2826 ± 412.3 kcal/day, carbohydrates 53.2 ± 1.4 %, fat 24.7 ± 3.1 %, protein 22.1 ± 2.6 %, ND
3007 ± 444.7 kcal/day, carbohydrates 54.7 ± 2.2 %, fat 23.9 ± 3.5 %, protein 21.4 ± 1.8). Subjects were tested before
and after 8 weeks of the assigned diet and standardized resistance training program. Fat mass and fat-free mass were
assessed by dual-energy x-ray absorptiometry and muscle area of the thigh and arm were measured using an anthro-
pometric system. Total and free testosterone, insulin-like growth factor 1, blood glucose, insulin, adiponectin, leptin,
triiodothyronine, thyroid stimulating hormone, interleukin-6, interleukin-1β, tumor necrosis factor α, total cholesterol,
high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides were measured. Bench
press and leg press maximal strength, resting energy expenditure, and respiratory ratio were also tested.
Results: After 8 weeks, the 2 Way ANOVA (Time * Diet interaction) showed a decrease in fat mass in TRF compared
to ND (p = 0.0448), while fat-free mass, muscle area of the arm and thigh, and maximal strength were maintained
in both groups. Testosterone and insulin-like growth factor 1 decreased significantly in TRF, with no changes in
ND (p = 0.0476; p = 0.0397). Adiponectin increased (p = 0.0000) in TRF while total leptin decreased (p = 0.0001),
although not when adjusted for fat mass. Triiodothyronine decreased in TRF, but no significant changes were detected
in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides.
© 2016 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,
provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/
publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Open Access
Journal of
Translational Medicine
*Correspondence: antonio.paoli@unipd.it
1
Department of Biomedical Sciences, University of Padova, Padua, Italy
Full list of author information is available at the end of the article

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et al. J Transl Med (2016) 14:290
Background
Fasting, the voluntary abstinence from food intake for a
specified period of time, is a well-known practice asso
-
ciated with many religious and spiritual traditions. In
fact, this ascetic practice is referenced in the Old Tes
-
tament, as well as other ancient texts such the Koran
and the Mahabharata. In humans, fasting is achieved
by ingesting little to no food or caloric beverages for
periods that typically range from 12h to 3weeks. Mus
-
lims, for example, fast from dawn until dusk during the
month of Ramadan, while Christians, Jews, Buddhists,
and Hindus traditionally fast on designated days or peri
-
ods [1]. Fasting is distinct from caloric restriction (CR),
in which daily caloric intake is chronically reduced by
up to 40%, but meal frequency is maintained [2]. In
contrast to fasting, starvation is a chronic nutritional
deficiency that is commonly incorrectly used as a sub
-
stitute for the term “fasting”. Starvation could also refer
to some extreme forms of fasting, which can result in
an impaired metabolic state and death. However, starva
-
tion typically implies chronic involuntary abstinence of
food, which can lead to nutrient deficiencies and health
impairment. While a prolonged period of fasting is dif
-
ficult to perform for the normal population, an inter-
mittent fasting (IF) protocol has been shown to produce
higher compliance [3]. Typically, IF is defined by a com
-
plete or partial restriction in energy intake (between 50
and 100% restriction of total daily energy intake) on
1–3days per week or a complete restriction in energy
intake for a defined period during the day that extends
the overnight fast. e most studied of the above form
of IF is Ramadan fasting: during the holy month of
Ramadan, which varies according to the lunar calendar,
Muslims abstain from eating or drinking from sunrise
to sunset. e effects of Ramadan have been extensively
investigated, not only on health outcomes [1, 4–8],
but also on exercise performance [9–16]. Moreover, in
recent years a focus on other forms of IF, unrelated to
religious practice, has emerged. One such form, alter
-
nate day fasting (ADF; fasting every other day) is organ-
ized with alternating “feast days,” on which there is an
“ad libitum” energy intake, and “fast days” with reduced
or null energy intake.
A growing body of evidence suggests that, in general,
IF could represent an useful tool for improving health
in general population due to reports of improving blood
lipids [17–20] and glycaemic control [3], reducing circu
-
lating insulin [21], decreasing blood pressure [1, 21–23],
decreasing inflammatory markers [7] and reducing fat
mass even during relatively short durations (8–12weeks)
[23]. ese reported effects are probably mediated
through changes in metabolic pathways and cellular
processes such as stress resistance [24], lipolysis [3, 17,
25–27], and autophagy [28, 29]. One particular form of IF
which has gained great popularity through mainstream
media is the so-called time-restricted feeding (TRF).
TRF allows subjects to consume adlibitum energy intake
within a defined window of time (from 3–4h to 10–12h),
which means a fasting window of 12–21 h per day is
employed. A key point concerning the IF approach is that
generally calorie intake is not controlled, but the feeding
times are.
In sports, IF is studied mainly in relationship with
Ramadan period [9–16], whilst TRF has become very
popular among fitness practitioners claiming supposed
effects on maintenance of muscle mass and fat loss. Very
limited scientific information is available about TRF
and athletes, and mixed results have been reported [22,
30, 31]. We demonstrated very recently [30] that TRF
did not affect total body composition nor had negative
effects on muscle cross-sectional area after 8 weeks in
young previously-untrained men performing resistance
training, despite a reported reduction in energy intake
of~650kcal per fasting day in the TRF group. us the
aim of the present study was to investigate the effects of
an isoenergetic TRF protocol on body composition, ath
-
letic performance, and metabolic factors during resist-
ance training in healthy resistance trained males. We
hypothesized that the TRF protocol would lead to greater
fat loss and improvements in health-related biomarkers
as compared to a typical eating schedule.
Methods
Subjects
irty-four resistance-trained males were enrolled
through advertisements placed in Veneto region’s gyms.
Resting energy expenditure was unchanged, but a significant decrease in respiratory ratio was observed in the TRF
group.
Conclusions: Our results suggest that an intermittent fasting program in which all calories are consumed in an 8-h
window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease
fat mass, and maintain muscle mass in resistance-trained males.
Keywords: Intermittent fasting, Time-restricted feeding, Resistance training, Body composition, Body builders,
Fasting

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et al. J Transl Med (2016) 14:290
e criteria for entering the study were that subjects
must have performed resistance training continuously
for at least 5years (training 3–5days/week with at least
3 years experience in split training routines), be pres
-
ently engaged in regular resistance training at the time
of recruitment, be life-long steroid free, and have no
clinical problems that could be aggravated by the study
procedures.
Fifty-three subjects responded to the advertisement,
but 7 were excluded for previous use of anabolic ster
-
oids, and 12 declined participation after explanation of
study’s protocol. erefore, 34 subjects (age 29.21±3.8;
weight 84.6±6.2kg) were randomly assigned to a time-
restricted feeding group (TRF; n=17) or standard diet
group (ND; n = 17) through computer-generated soft
-
ware. e research staff conducting outcome assessments
was unaware of the assignment of the subjects (i.e. a sin
-
gle blind design). Anthropometric baseline character-
istics of subjects are shown in Table1. All participants
read and signed an informed consent document with the
description of the testing procedures approved by the
ethical committee of the Department of Biomedical Sci
-
ences, University of Padova, and conformed to standards
for the use of human subjects in research as outlined in
the current Declaration of Helsinki.
Diet
Dietary intake was measured by a validated 7-day food
diary [32–34], which has been used in previous stud
-
ies with athletes [35], and analysed by nutritional soft-
ware (Dietnext
®
, Caldogno, Vicenza, Italy). Subjects
were instructed to maintain their habitual caloric intake,
as measured during the preliminary week of the study
(Table2). During the 8-week experimental period, TRF
subjects consumed 100% of their energy needs divided
into three meals consumed at 1p.m., 4p.m. and 8p.m.,
and fasted for the remaining 16h per 24-h period. ND
group ingested their caloric intake as three meals con
-
sumed at 8a.m., 1p.m. and 8p.m. is meal timing was
chosen to create a balanced distribution of the three
meals during the feeding period in the TRF protocol,
while the schedule for the ND group maintained a nor
-
mal meal distribution (breakfast in the morning, lunch at
1p.m. and dinner at 8p.m.). e distribution of calories
was 40, 25, and 35% at 1p.m., 4p.m. and 8p.m. respec
-
tively for TRF, while ND subjects consumed 25, 40 and
35% of daily calories at 8a.m., 1p.m. and 8p.m. respec
-
tively. e specific calorie distribution was assigned by a
nutritionist and was based on the reported daily intake of
each subject.
ND subjects were instructed to consume the entire
breakfast meal between 8 a.m. and 9 a.m., the entire
lunch meal between 1p.m. and 2p.m., and the entire din
-
ner meal between 8p.m. and 9p.m. TRF subjects were
instructed to consume the first meal between 1 p.m.
and 2p.m., the second meal between 4p.m. and 5p.m.,
and the third meal between 8p.m. and 9p.m. No snacks
between the meals were allowed except 20g of whey pro
-
teins 30min after each training session. Every week, sub-
jects were contacted by a dietician in order to check the
adherence to the diet protocol. e dietician performed a
structured interview about meal timing and composition
to obtain this information.
Table 1 Subject characteristics atbaseline
Results presented as mean±SD. Results are not statistically signicantly
dierent
TRF ND
Age 29.94 ± 4.07 28.47 ± 3.48
Weight (kg) 83.9 ± 12.8 85.3 ± 13
Height (cm) 178 ± 5 177 ± 4
FM (kg) 10.9 ± 3.5 11.3 ± 4.5
FFM (kg) 73.1 ± 5.7 73.9 ± 3.9
Table 2 Diet composition andmacronutrients distribution at basal level andduring the experimental period in both
groups
Results presented as mean±SD. No signicant dierences were detected between groups and within groups
TRF basal TRF exp ND basal ND exp
Total (kcal/day) 2826 ± 412.3 2735 ± 386 3007 ± 444.7 2910 ± 376.4
Carbohydrates (kcal/day) 1503.4 ± 225.95 1400.3 ± 118.8 1654 ± 222.4 1609.2 ± 201.5
Fat (kcal/day) 698 ± 178.5 683.8 ± 61.6 728.7 ± 195 647.7 ± 183.4
Protein (kcal/day) 624.5. ± 59.5 650.3. ± 62.5 637 ± 72.9 643.1 ± 69.3
% Carbohydrates 53.2 ± 1.4 51.2 ± 3.6 54.7 ± 2.2 55.3 ± 4.2
% Fat 24.7 ± 3.1 25 ± 2.8 23.9 ± 3.5 22.6 ± 3.2
% Protein 22.1 ± 2.6 23.8 ± 3.1 21.4 ± 1.8 22.1 ± 3.2
Protein (g/kg
bw
) 1.86 ± 0.2 1.93 ± 0.3 1.9 ± 0.3 1.89 ± 0.4

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et al. J Transl Med (2016) 14:290
Training
Training was standardized for both groups, and all sub-
jects had at least 5years of continuous resistance train-
ing experience prior to the study. Training consisted of 3
weekly sessions performed on non-consecutive days for
8weeks. All participants started the experimental proce
-
dures in the months of January or February 2014.
e resistance training program consisted of 3 differ
-
ent weekly sessions (i.e. a split routine): session A (bench
press, incline dumbell fly, biceps curl), session B (mili
-
tary press, leg press, leg extension, leg curl), and session
C (wide grip lat pulldown, reverse grip lat pulldown and
tricep pressdown). e training protocol involved 3 sets
of 6–8 repetitions at 85–90 % 1-RM, and repetitions
were performed to failure (i.e. the inability to perform
another repetition with correct execution) with 180s of
rest between sets and exercises [36]. e technique of
training to muscular failure was chosen because it is one
of the most common practices for body builders, and it
was a familiar technique for the subjects. As expected,
the muscle action velocity varied between subjects due to
their different anatomical leverage. Although there was
slight variation of repetition cadence for each subject, the
average duration of each repetition was approximately
1.0s for the concentric phase and 2.0s for the eccentric
phase [37].
e research team directly supervised all routines to
ensure proper performance of the routine. Each week,
loads were adjusted to maintain the target repetition
range with an effective load. Training sessions were per
-
formed between 4:00 and 6:00 p.m. Subjects were not
allowed to perform other exercises other than those
included in the experimental protocol.
Measurements
Body weight was measured to the nearest 0.1kg using an
electronic scale (Tanita BWB-800 Medical Scales, USA),
and height to the nearest 1 cm using a wall-mounted
Harpenden portable stadiometer (Holtain Ltd, UK). Body
mass index (BMI) was calculated in kg/m
2
. Fat mass and
fat-free mass were assessed by dual energy X-ray absorp
-
tiometry (DXA) (QDR 4500 W, Hologic Inc., Arling-
ton, MA, USA). Muscle areas were calculated using the
following anthropometric system. We measured limb
circumferences to the nearest 0.001m using an anthro
-
pometric tape at the mid-arm and mid-thigh. We also
measured biceps, triceps, and thigh skinfolds to the near
-
est 1mm using a Holtain caliper (Holtain Ltd, UK). All
measurements were taken by the same operator (AP)
before and during the study according to standard pro
-
cedures [38, 39]. Muscle areas were then calculated using
a previously [40] validated software (Fitnext
®
, Caldogno,
Vicenza, Italy). Cross-sectional area (CSA) measured
with Fitnext
®
has an r
2
=0.88 compared to magnetic res-
onance and an ICC of 0.988 and 0.968 for thigh and arm,
respectively [40–42].
Ventilatory measurements were made by standard
open-circuit calorimetry (max Encore 29 System, Vmax,
Viasys Healthcare, Inc., Yorba Linda, CA, USA) with
breath-by-breath modality. e gas analysis system was
used: Oxygen uptake and carbon dioxide output val
-
ues were measured and used to calculate resting energy
expenditure (REE) and respiratory ratio (RR) using the
modified Weir equation [43]. Before each measurement,
the calorimeter was warmed according to the manufac
-
turer’s instructions and calibrated with reference gases of
known composition prior to each participant.
Oxygen uptake was measured (mL/min) and also nor
-
malized to body weight (mL/kg/min), and the respira-
tory ratio was determined. After resting for 15min, the
data were collected for 30min, and only the last 20min
were used to calculate the respiratory gas parameters [37,
44]. All tests were performed in the morning between 6
and 8a.m. while the subjects were supine. e room was
dimly lit, quiet, and approximately 23°C. Subjects were
asked to abstain from caffeine, alcohol consumption
and from vigorous physical activity for 24h prior to the
measurement.
Blood collection andanalysis protocol
Blood samples taken from the antecubital vein at base-
line and after 8weeks were collected in BD Vacutainers
Tubes (SST
™
II Advance, REF 367953). Samples were
centrifuged (4000 RPM at 4°C using centrifuge J6-MC
by Beckman), and the resultant serum was aliquoted
and stored at −80°C. All samples were analysed in the
same analytical session for each test using the same rea
-
gent lot. Before the analytical session, the serum sam-
ples were thawed overnight at 4 °C and then mixed.
Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α),
and interleukin-1β (IL-1β) were measured using Quan
-
tikine HS Immunoassay Kit (R&D Systems, Minneapo-
lis, MN, USA). e inter-assay coefficient of variations
(CVs) were 3.5–6.2 and 3.2–6.3% for IL-6, TNF-α and
IL-1β respectively. Insulin-like growth factor 1 (IGF-1)
was measured using the analyzer Liaison XL (DiaSorin
S.p.A, Vercelli-Italy). is test is a sandwich immunoas
-
say based on a chemiluminescent revelation, and the CV
for IGF-1 was between 5.6 and 9.6%; the reference range
for this test depends on age and gender. Fasting total cho
-
lesterol, high-density lipoprotein cholesterol (HDL-C),
low-density lipoprotein cholesterol (LDL-C), and triglyc
-
erides (TG) were measured by an enzymatic colorimet-
ric method using a Modular D2400 (Roche Diagnostics,
Basel, Switzerland). LDL-C fraction was calculated from
Friedewald’s formula: LDL-C=TC−HDL-C−(TG/5).