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Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT)

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Objectives To compare the effects of interval training and moderate-intensity continuous training (MOD) on body adiposity in humans, and to perform subgroup analyses that consider the type and duration of interval training in different groups. Design Systematic review and meta-analysis. Data sources English-language, Spanish-language and Portuguese-language searches of the electronic databases PubMed and Scopus were conducted from inception to 11 December 2017. Eligibility criteria for selecting studies Studies that met the following criteria were included: (1) original articles, (2) human trials, (3) minimum exercise training duration of 4 weeks, and (4) directly or indirectly compared interval training with MOD as the primary or secondary aim. Results Of the 786 studies found, 41 and 36 were included in the qualitative analysis and meta-analysis, respectively. Within-group analyses showed significant reductions in total body fat percentage (%) (interval training: −1.50 [95% CI −2.14 to −0.86, p<0.00001] and MOD: −1.44 [95% CI −2.00 to −0.89, p<0.00001]) and in total absolute fat mass (kg) (interval training: −1.58 [95% CI −2.74 to −0.43, p=0.007] and MOD: −1.13 [95% CI −2.18 to −0.08, p=0.04]), with no significant differences between interval training and MOD for total body fat percentage reduction (−0.23 [95% CI −1.43 to 0.97], p=0.705). However, there was a significant difference between the groups in total absolute fat mass (kg) reduction (−2.28 [95% CI −4.00 to −0.56], p=0.0094). Subgroup analyses comparing sprint interval training (SIT) with MOD protocols favour SIT for loss of total absolute fat mass (kg) (−3.22 [95% CI −5.71 to −0.73], p=0.01). Supervised training, walking/running/jogging, age (<30 years), study quality and intervention duration (<12 weeks) favourably influence the decreases in total absolute fat mass (kg) observed from interval training programmes; however, no significant effect was found on total body fat percentage (%). No effect of sex or body mass index was observed on total absolute fat mass (kg) or total body fat percentage (%). Conclusion Interval training and MOD both reduce body fat percentage (%). Interval training provided 28.5% greater reductions in total absolute fat mass (kg) than MOD. Trial registration number CRD42018089427.
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1
VianaRB, etal. Br J Sports Med 2019;0:1–12. doi:10.1136/bjsports-2018-099928
Is interval training the magic bullet for fat loss? A
systematic review and meta-analysis comparing
moderate-intensity continuous training with high-
intensity interval training(HIIT)
Ricardo Borges Viana,1 João Pedro Araújo Naves,1 Victor Silveira Coswig,2
Claudio Andre Barbosa de Lira,1 James Steele,3 James Peter Fisher,3 Paulo Gentil1
Review
To cite: VianaRB,
NavesJPA, CoswigVS, etal.
Br J Sports Med Epub ahead
of print: [please include Day
Month Year]. doi:10.1136/
bjsports-2018-099928
Additional material is
published online only. To view
please visit the journal online
(http:// dx. doi. org/ 10. 1136/
bjsports- 2018- 099928).
1Faculty of Physical Education
and Dance, Federal University of
Goiás, Goiânia, Goiás, Brazil
2Faculty of Physical Education,
Federal University of Pará,
Castanhal, Pará, Brazil
3Centre for Health, Exercise, and
Sport Science, School of Sport,
Health and Social Sciences,
Southampton, Hampshire, UK
Correspondence to
DrPaulo Gentil, Faculdade
de Educação Física e Dança,
Universidade Federal de Goiás,
Goiania 74605-220, Brazil;
paulogentil@ hotmail. com
Accepted 14 December 2018
© Author(s) (or their
employer(s)) 2019. No
commercial re-use. See rights
and permissions. Published
by BMJ.
ABSTRACT
Objectives To compare the effects of interval training
and moderate-intensity continuous training (MOD) on
body adiposity in humans, and to perform subgroup
analyses that consider the type and duration of interval
training in different groups.
Design Systematic review and meta-analysis.
Data sources English-language, Spanish-language
and Portuguese-language searches of the electronic
databases PubMed and Scopus were conducted from
inception to 11 December 2017.
Eligibility criteria for selecting studies Studies
that met the following criteria were included: (1)
original articles, (2) human trials, (3) minimum exercise
training duration of 4 weeks, and (4) directly or indirectly
compared interval training with MOD as the primary or
secondary aim.
Results Of the 786 studies found, 41 and 36 were
included in the qualitative analysis and meta-analysis,
respectively. Within-group analyses showed significant
reductions in total body fat percentage (%) (interval
training: −1.50 [95% CI −2.14 to −0.86, p<0.00001]
and MOD: −1.44 [95% CI −2.00 to −0.89, p<0.00001])
and in total absolute fat mass (kg) (interval training:
−1.58 [95% CI −2.74 to −0.43, p=0.007] and MOD:
−1.13 [95% CI −2.18 to −0.08, p=0.04]), with no
significant differences between interval training and
MOD for total body fat percentage reduction (−0.23
[95% CI −1.43 to 0.97], p=0.705). However, there was
a significant difference between the groups in total
absolute fat mass (kg) reduction (−2.28 [95% CI −4.00
to −0.56], p=0.0094). Subgroup analyses comparing
sprint interval training (SIT) with MOD protocols favour
SIT for loss of total absolute fat mass (kg) (−3.22 [95%
CI −5.71 to −0.73], p=0.01). Supervised training,
walking/running/jogging, age (<30 years), study quality
and intervention duration (<12 weeks) favourably
influence the decreases in total absolute fat mass (kg)
observed from interval training programmes; however,
no significant effect was found on total body fat
percentage (%). No effect of sex or body mass index was
observed on total absolute fat mass (kg) or total body fat
percentage (%).
Conclusion Interval training and MOD both reduce
body fat percentage (%). Interval training provided
28.5% greater reductions in total absolute fat mass (kg)
than MOD.
Trial registration number CRD42018089427.
INTRODUCTION
Whether physical activity affects weight control
has been an ongoing topic of controversy.1 2 The
majority of physical activity guidelines for the
management of obesity recommend high exer-
cise volumes.3 4 Guidelines generally recommend
150–250 min/week, and up to 60 min/day, of moder-
ate-intensity aerobic exercise to prevent weight gain
or to reduce body mass a little bit (2–3 kg).4 5 More
than an hour of exercise daily (>420 min/week)
is recommended to lose more weight (5–7.5 kg)3
and few people meet these guidelines.6 7
Interval training may have the potential to
promote weight loss as it has some benefits
similar to moderate-intensity continuous training
(MOD) while requiring less time.8 9 MOD is
typically defined as continuous effort that elicits
55%–70% of the maximal heart rate (HRmax) or
promotes oxygen consumption (
V
O2) equivalent
to 40%–60% of the maximum
V
O2 (
V
O2max).10
Interval training is an intermittent period of effort
interspersed by recovery periods11; the two most
common types of interval training are high-inten-
sity interval training (HIIT) and sprint interval
training (SIT).7 HIIT requires ‘near maximal’
efforts performed at a heart rate (HR) ≥80%
of the HRmax or the equivalent as expressed in
the function of the
V
O2max. Even more intense
exercise, SITs are efforts performed at intensities
equal or superior to the one that elicited a peak
V
O2 on an incremental test (i
V
O2peak), including
‘all-out’ efforts.7 12
HIIT programmes, when compared with
MOD, promote greater increases in
V
O2max,13
ventricular and endothelial function,14 greater
or comparable improvements in insulin sensi-
tivity15 and blood pressure,16 lower ratings of
perceived exertion,17 similar6 or higher levels of
enjoyment,17 18 and similar6 or higher adherence18
than MOD, depending on how the programme is
designed. In addition, despite lower training volume
in SIT programmes, SIT may promote increases in
skeletal muscle oxidative capacity,19 specific meta-
bolic adaptations during exercise19 and exercise
performance similar to MOD.20
Decreases in body fat may be similar21 or higher22
in interval training than MOD. Interval training
may elicit greater weight loss even if the energy
expenditure obtained during the interval training is
lower23 or equal24 to that during MOD. This may
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2VianaRB, etal. Br J Sports Med 2019;0:1–12. doi:10.1136/bjsports-2018-099928
Review
be due to greater resting energy expenditure and fat utilisation
immediately following interval training exercise.25 26 However,
there are currently many different approaches to performing
interval training,27 and there is still no consensus as to which
training method (HIIT/SIT vs MOD) is best to reduce body
fat. The considerable variability among interval training proto-
cols,27 compared with fairly homogeneous MOD protocols,
introduce ‘noise’ in the literature. No study has yet addressed the
simple question: Which type of exercise is better for weight loss?
We conducted a systematic review, qualitative appraisal and
meta-analysis of studies that directly or indirectly compared the
effects of HIIT or SIT with MOD on adiposity. We compared
subgroups to test whether (1) the nature of the interval training
(HIIT or SIT), (2) sex, (3) baseline body mass index (BMI) or
other variables influenced the outcome. We hypothesised that
HIIT/SIT would reduce body fat more effectively than MOD.
METHODS
The results of this systematic review and meta-analysis are
presented according to the Preferred Reporting Items for System-
atic Reviews and Meta-Analyses statement,28 and was prereg-
istered in the International Prospective Register of Systematic
Review (PROSPERO).29
Search strategy
English-language, Spanish-language and Portuguese-language
searches of the electronic databases PubMed and Scopus were
conducted from inception to 11 December 2017 by two inde-
pendent researchers (RBV and JPAN). Articles were retrieved
from electronic databases using the following search criteria:
(interval training OR intermittent training OR high intensity
OR sprint interval training OR aerobic interval training HIIT
OR HIIE OR high intensity interval training OR high-intensity
interval training OR high intensity interval exercise OR high-in-
tensity interval exercise OR high intensity intermittent exercise
OR high-intensity intermittent exercise OR high intensity inter-
mittent training OR high-intensity intermittent training) AND
(continuous training OR moderate-intensity continuous exercise
OR moderate intensity continuous exercise OR moderate-in-
tensity continuous training OR moderate intensity continuous
training) AND (body fat OR adiposity OR body composition OR
abdominal fat OR visceral fat OR adipose tissue) AND Humans.
Initially, titles and abstracts of identified studies were checked
for relevance by two reviewers (RBV and JPAN). Subsequently,
the reviewers independently reviewed the full text of potentially
eligible studies. Any disagreement for inclusion between the
reviewers was resolved by a third researcher (PG). Additional
studies were identified via hand-searching and reviewing the
reference lists of relevant papers. All these steps were performed
for 3 weeks. Figure 1 presents the flow of papers through the
study selection process.
Inclusion and exclusion criteria: participants, interventions,
comparators andoutcomes
Studies with participants of all ages and sexes with a minimum
exercise training duration of 4 weeks, which directly or indirectly
compared HIIT or SIT with MOD as the primary or secondary
aim (according to previous definitions), and which evaluated fat
change by methods that infer total or regional mass, or total
or regional percentage fat, were included. Studies that reported
only BMI and that compared HIIT or SIT or MOD with only
non-training control groups were not included for analysis. When
employing two interval training protocols, both were included,
in different analyses, for comparison with MOD. Studies were
excluded based on the following article types: letters to the
editor, books, book sections, theses, film/broadcasts, opinion
articles, observational studies and abstracts without adequate
data, or reviews.
Data extraction
The following study characteristics were extracted: age, sex,
body mass, BMI,
V
O2max/peak, total or regional fat mass (kg),
percentage total and regional body fat (%), and HIIT/SIT and
MOD interventions characteristics. These data were extracted
independently by two researchers (RBV and JPAN), with
disagreements resolved by a third researcher (PG). When studies
provided insufficient data for inclusion in the meta-analysis (five
studies), the corresponding authors were contacted via email to
determine whether additional data could be provided; however,
no corresponding authors responded.
Study quality assessment
Study quality was assessed by two researchers (RBV and JPAN)
using a modified Downs and Black checklist.30 Items included
the appropriate reporting of the hypotheses, outcomes, inter-
ventions, adverse events, participant characteristics (a clear state-
ment on inclusion and exclusion criteria), descriptions of patients
lost to follow-up (studies with ≥10% dropout without charac-
teristics reported scored 0), assessment method accuracy, statis-
tical methods, blinding and randomisation procedures. The scale
was modified to include criteria for monitoring and reporting of
physical activity level (yes=1, no=0) and diet (yes=1, no=0),
the supervision of exercise sessions (yes=1, no=0), and infor-
mation about adherence and/or compliance to exercise inter-
ventions (yes=1, no=0). Therefore, the studies that monitored
and reported control of diet, habitual activity, supervision, and
adherence or compliance scored 1 point in each item. If an item
was unable to be determined, it was scored as 0. The highest
possible score for quality was 20. In addition, we recorded the
strengths/weakness/unknowns of available information from
studies to strengthen the quality analysis of the included studies.
Statistical analyses
All analyses were conducted using the R package (V.3.2.4).
Meta-analysis was conducted using a random-effects model
(DerSimonian and Laird approach) for the individual effects of
HIIT/SIT and MOD on total body fat (kg) and body fat percentage.
The random-effects model was preferred to a fixed-effect model
as certain experimental parameters had wide variation. For the
secondary meta-analysis, premeans, postmeans, absolute and
relative changes, and SD for each group were collected. Initially,
a within-group effect size (ES) was calculated using a random-ef-
fects model (DerSimonian and Laird approach) to estimate
the change from baseline for each group, given that a random-ef-
fects model considers true random errors within a single study
and variation in effects occurring from study to study. The statis-
tical heterogeneity of the treatment effect among studies was
assessed using Cochran’s Q test and the inconsistency I2 test, in
which values above 30% and 50% were considered indicative of
moderate and high heterogeneity, respectively.31 Publication bias
was assessed with funnel plots and Begg’s test. To improve our
results, we conducted several sensitivity analyses to consider the
individual influence of each study on the overall results, as well
as the type of comparison group (HIIT or SIT), type of modality
(walking/jogging/running or cycling), age (<30 and ≥30 years),
sex, BMI (<30 kg/m2 and ≥30 kg/m2), intervention duration
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Review
(<12 and ≥12 weeks), study quality (‘low, middle and high’) and
supervision of exercise sessions (yes and no).
RESULTS
Included studies
The search strategy retrieved 786 records. After deduplication
and language examination (English, Spanish and Portuguese
studies), 24 studies were excluded from the review process and
698 were excluded after title and/or abstract analysis; 64 full-
text copies of the remaining studies were obtained and subjected
to further evaluation. After reading full-text copies, 23 studies
were excluded from this review due to the following reasons:
(1) four studies included MOD in combination with the HIIT
protocol23 32–34; (2) one study did not perform MOD35; (3)
four studies applied an HIIT or MOD intervention combined
with other activities36–39; (4) five studies did not use the MOD
criteria adopted in this review40–44; (5) five studies stated the
use of HIIT or SIT protocols,45–49 but did not match the HIIT
and SIT criteria adopted in this review; (6) three studies did not
assess body fat50–52; and (7) one study did not present separate
body composition data.53 At the end of the process, 41 publica-
tions meeting the eligibility criteria were included for qualitative
analyses,22 52–91 of which 5 studies provided insufficient data and
were excluded from this review due to the following reasons: (1)
two studies did not provide SD for change in mean values67 92; (2)
two studies reported only regional body fat percentage (%)58 84;
and (3) one study provided only skinfold values.55 Therefore, 36
studies provided sufficient data for meta-analysis (35 for total
body fat percentage [%] and 15 for total absolute fat mass [kg])
(figure 1).
Participant characteristics
Participants’ characteristics are summarised in table 1. Overall,
1115 participants were included in the qualitative anal-
ysis and 1012 in the meta-analysis. The number of partici-
pants in the studies varied from 768 to 90.78 Fourteen studies
examined exclusively males,55 59 66 67 69 72 73 75 77 79–81 88 92 nine
exclusively females,24 63 65 74 82 83 87 90 93 one did not report the
number of males and females used to present the body compo-
sition results,84 while the remaining studies (n=17) assessed a
mixed-sex sample.44 54 56–58 60–62 64 68 70 71 76 78 85 86 89 91 In total,
576 males and 522 females participated in the studies. Two
studies used the same sample,61 62 and one performed a double-
blind, randomised, crossover investigation with seven athletes
(five males and two females).68 The mean age of study partici-
pants ranged from 10.464 to 70.1 years.87 The training status of
Figure 1 Flow diagramof outcomes of review. HIIT,high-intensity interval training; MOD,moderate-intensity continuous training; SIT,sprint interval
training.
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Review
Table 1 Characteristics of the participants
Reference Participants*
Male (%)/
Female (%) Age (year) BMI (kg/m2) Other population characteristics
Thomas et al54 29 38/62 18–32 NR Healthy, untrained but active young adults
Mäder et al55 14 100/0 HIIT: 28–46
MOD: 28–46
HIIT: 25.9 (3.2)
MOD: 26.9 (3.3)
Untrained butslightly overweight
Trapp et al24 30 0/100 20.2 (7.7) 23.2 (7.7) Healthy, untrained young
Schjerve et al56 27 22/78 HIIT: 46.9 (8.2)
MOD: 44.4 (7.6)
HIIT: 36.6 (5.5)
MOD: 36.7 (5.1)
Adults with obesity
Moreira et al57 16 36/64 40 (8) HIIT: 28.3 (3.7)
MOD: 27.5 (1.9)
Healthy, overweight
Wallman et al58 13 31/69 HIIT: 40.9 (11.7)
MOD:44.8 (16.8)
HIIT: 31.4 (2.6)
MOD: 30.1 (2.6)
Overweight/obeseadults
Nybo et al59 17 100/0 HIIT: 37.0 (8.5)
MOD: 31.0 (6.0)
NR Healthy untrained
Macpherson et al60 20 40/60 24.0 (3.0) NR Healthy, recreationally active university students
Buchan et al61 33 82/18 SIT: 16.7 (0.1)
MOD: 16.2 (0.1)
SIT: 21.6 (2.2)
MOD: 22.4 (3.3)
Adolescents
Buchan et al62 33 82/18 SIT: 16.7 (0.1)
MOD: 16.2 (0.1)
SIT: 21.6 (2.2)
MOD: 22.4 (3.3)
Adolescents
Sijie et al63 33 0/100 HIIT: 19.8 (1.0)
MOD: 19.3 (0.7)
HIIT: 27.7 (1.9)
MOD: 28.3 (2.0)
Overweight/obeseyoung
Corte de Araujo et al64 30 30/70 HIIT: 10.4 (0.9)
MOD: 10.7 (0.7)
HIIT: 32.0 (3.0)
MOD: 30.0 (4.0)
Children with obesity
Eimarieskandari et al65 14 0/100 HIIT: 22.3 (0.9)
MOD: 21.4 (0.5)
HIIT: 29.2 (0.8)
MOD: 30.7 (2.3)
Young adults with obesity
Koubaa et al66 29 100/0 HIIT: 13.0 (0.8)
MOD: 12.9 (0.5)
HIIT: 30.2 (3.6)
MOD: 30.8 (2.9)
Adolescent boys with obesity
Earnest et al67 37 100/0 HIIT: 48 (9)
MOD: 49 (9)
HIIT: 30.4 (2.3)
MOD: 31.4 (3.4)
Adults
Shing et al68§ 7 71/29 19.0 (1.2) NR Junior state-level and national-level rowers
Shepherd et al69 16 100/0 SIT: 22.0 (2.8)
MOD: 21.0 (2.8)
SIT: 24.8 (2.3)
MOD: 22.6 (4.5)
Healthy and inactive adults
Keating et al70 22 23/77 HIIT: 41.8 (2.7)
MOD: 44.1 (1.9)
HIIT: 28.2 (0.5)
MOD: 28.5 (0.6)
Inactive,overweight adults
Lunt et al71 49 27/73 HIIT: 48.2 (5.6)
MOD: 46.3 (5.4)
SIT: 50.3 (8.0)
HIIT: 32.1 (3.1)
MOD: 32.7 (3.4)
SIT: 32.4 (2.9)
Inactive, overweight/obese adults
Nalcakan72 15 100/0 21.7 (2.2) SIT: 25.5 (2.2)
MOD: 24.5 (1.9)
Healthy and young recreationally active university
students
Sasaki et al73 24 100/0 NR HIIT: 24.3 (0.7)
MOD: 23.4 (0.8)
Healthy and sedentary
Mohr et al74 42 0/100 SIT: 44 (2)
MOD: 46 (2)
>25.0 Sedentary premenopausal women with mild to moderate
arterial hypertension
Cocks et al75 16 100/0 25.0 (2.8) 34.8 (0.9) Inactive young with obesity
Cheema et al76 12 58/42 HIIT: 43 (19)
MOD: 36 (15)
HIIT: 32.0 (5.9)
MOD: 30.8 (2.6)
Inactive adults with central obesity
Elmer et al77 12 100/0 HIIT: 21.4 (1.1)
MOD: 21.8 (2.1)
HIIT: 24.7 (2.9)
MOD: 27.1 (4.8)
Healthy sedentary or inactive adults
Shepherd et al78 90 33/67 HIIT: 42.0 (11)
MOD: 43 (11)
HIIT: 27.7 (5.0)
MOD: 27.7 (4.6)
Healthy and inactive adults
Fisher et al79 23 100/0 HIIT: 20.0 (1.5)
MOD: 20.0 (1.5)
HIIT: 30.0 (3.1)
MOD: 29.0 (3.4)
Inactive,overweight/obese young men
Sim et al80 20 100/0 31.8 (8.0) HIIT: 27.4 (1.6)
MOD: 27.2 (1.5)
Inactive,overweight/obese adult participants
Devin et al81 35 100/0 HIIT: 61.4 (11.1)
MOD:61.5 (10.8)
HIIT: 27.1 (4.8)
MOD: 26.4 (3.4)
Colorectal cancer survivors
Zhang et al82 24 0/100 HIIT: 21.0 (1.0)
MOD: 20.6 (1.2)
HIIT: 25.8 (2.7)
MOD: 26.0 (1.6)
Chinese ethnicity, inactive, overweight/obese
Gillen et al83 18 0/100 SIT: 27 (7)
MOD: 28 (9)
SIT: 27 (5)
MOD: 26 (6)
Inactive
Martins et al84 17† NR SIT: 33.9 (7.8)
1/2SIT: 34.1 (7.1)
MOD: 33.0 (9.9)
SIT: 33.2 (3.5)
1/2SIT: 32.4 (2.9)
MOD: 33.3 (2.4)
Inactive adults with obesity
Continued
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the participants ranged from sedentary73 to high-level athletes.68
The mean BMI ranged from 18.4 kg/m291 to 36.7 kg/m2.56
Intervention characteristics
The interval training and MOD programmes are summarised in
online supplementary table S1. According to the criteria of HIIT and
SIT adopted in this review,7 12 2554–59 63–68 70 73 76–78 81 82 85–87 90 92 93
and 1524 60–62 69 72 74 75 79 80 83 84 88 89 91 of the 41 included studies
employed HIIT and SIT interventions, respectively. Only one
study71 employed both HIIT and SIT interventions, and one
study included two HIIT interventions.86 Of the 41 studies, 20
used cycling,24 55 57 58 69 70 72 73 75 78–81 83 84 87–90 93 16 used walking/
jogging/running,54 56 59–67 71 77 82 91 92 1 used a synchronous arm
and leg air-braked ergometer,85 1 offered a choice between the
two (cycle ergometer or walking/running) depending on ortho-
paedic limitations,86 1 used swimming,74 1 used boxing drills for
the HIIT protocol and walking for MOD,76 and 1 used a rower
ergometer.68 Intervention duration ranged from 468 73 75 81 to
16 weeks,86 87 with 12 weeks being the most common (~44%;
n=18)54 56 57 59 63 64 66 67 70 71 76 80 82–84 89 92 93 (online supple-
mentary table S1). The most widely used HIIT (n=8) protocol
consisted of alternating 4 min at high intensity followed by 3 min
of recovery.56 65 71 81 82 85 86 93 The most widely used SIT protocols
consisted of alternating 30 s ‘all-out’ efforts followed by 4 min
of recovery,60 79 88 and protocols that alternate 8 s ‘all-out’ efforts
followed by 12 s of recovery.24 84 The MOD protocols used lasted
from 1024 to 60 min,59 74 with 40–45 min (n=6)63 65 70 76 83 87 and
29–35 min (n=6)71 77 82 85 86 90 being the most used protocols.
Twenty-two HIIT protocols used active
recovery,54–56 58 63–65 67 68 70 76–78 81 82 84–87 89 90 92 one used
passive recovery,93 and five did not report clearly what type of
recovery was used.57 59 66 73 91 Eight SIT protocols used active
recovery,54 60 69 75 79 80 83 88 one used passive recovery,74 and three
did not report clearly what type of recovery was used.61 62 72 The
only study to employ HIIT versus SIT versus MOD protocols71
used active recovery in both the interval training protocols.
The intensity of effort for HIIT protocols was prescribed by
the percentage of i
V
O2max66 67 77 or i
V
O2peak,58 percentage of
V
O2max55 63 73 or
V
O2peak,70 percentage of HRmax54 56 59 71
78 87 90 92 93 or peak heart rate (HRpeak),64 65 81 82 85 86 rating of
perceived exertion,76 HR corresponding to 20% above the HR at
ventilatory threshold,57 and 90% of 4 min maximal power.68 The
intensity of effort in most SIT protocols (n=13) was prescribed
by ‘all-out’ efforts,24 60–62 69 71 72 74 83 84 88 89 91 percentage of
i
V
O2peak,80 percentage of maximal power output75 and
percentage of anaerobic power.79
More than half of the protocols (~63%; n=26) were performed
three times per week.24 54–57 59–62 65 66 70–74 77 80 81 83 84 88–92 Four
protocols were performed four times per week,58 76 82 85 two
protocols were performed three to four times per week,67 93 three
protocols were performed twice a week,64 68 87 one protocol was
performed five times per week,63 and five MOD protocols had a
frequency greater (five times per week) than the interval training
protocols (three times per week).69 75 78 79 86
Diet and physical activity control
Almost half of the studies (~42%; n=17) instructed participants
to maintain both normal diet and physical activity.24 60 61 63 69 70
72 73 77 78 81 84 85 87 90 91 93 Twenty-three (~56%) and 19 (~46%)
studies reported a diet24 55 58 61 62 64 65 67–71 73 80 82 84 86–88 90–93 and
physical activity control,56 58 62 67 68 70 71 73 78 80–82 84–88 91 93 respec-
tively (online supplementary table S2). One study provided a
1-hour diet education session per week.58 In addition, one study
employed a caloric reduction of 500 kcal/day based on partic-
ipants’ normal intake.92 Online supplementary table S1 shows
additional information about diet and physical activity of the
participants of the included studies.
Body composition assessments
Most studies (~56%; n=23) used only dual-energy X-ray
absorptiometry (DXA) to determine total and/or android, trunk
Reference Participants*
Male (%)/
Female (%) Age (year) BMI (kg/m2) Other population characteristics
Hwang et al85 29 41/59 65 (7.1) HIIT: 28.0 (4.3)
MOD: 28.7 (3.7)
Inactive and healthy older adults
Ramos et al86 66 63/37 4HIIT: 56 (10)
1HIIT: 58 (7)
MOD: 57 (9)
4HIIT: NR
1HIIT: NR
MOD: NR
Adults with metabolic syndrome
Maillard et al87 16 0/100 HIIT: 68.2 (1.9)
MOD: 70.1 (2.4)
HIIT: 32.6 (1.7)
MOD: 29.7 (1.2)
Postmenopausal and obese (61–81 years) women with
type 2diabetes
Higgins et al88 52 100/0 20.4 (1.5) 30.3 (4.5) Inactive, overweight/obese women
Boer and Moss89 26 58/42 SIT: 30.0 (7.0)
MOD: 34.2 (9.2)
SIT: 29.3 (4.0)
MOD: 30.6 (6.1)
Adults with Down syndrome
Panissa et al90 23 0/100 HIIT: 30.6 (15.1)
MOD: 26.1 (9.1)
HIIT: 25.9 (4.1)
MOD: 23.3 (2.3)
Inactive healthy women
Camacho-Cardenosa et al91 34 54/46‡ SIT: 11.1 (0.2)
MOD: 11.3 (0.5)
SIT: 18.4 (2.8)
MOD: 20.1 (3.3)
Adolescents
Zhang et al93 30 0/100 HIIT: 21.5 (1.7)
MOD: 20.9 (1.4)
≥25 Obese young women
Galedari et al92 22 100/0 HIIT: 30.8 (7.6)
MOD: 28.8 (6.1)
HIIT: 29.6 (1.5)
MOD: 28.9 (1.3)
Overweight men
*Number included in HIIT/SIT versus MOD for body composition analysis.
†n=17 for body composition analysis in HIIT versus MOD.
‡Percentage referring to 35 participants.Values reported as mean.
§Double-blind, randomised, crossover investigation.
1/2SIT,approximately half of time of the sprint interval training; 1HIIT,high-intensity interval training (one bout); 4HIIT,high-intensity interval training (four bouts); BMI,
body mass index; HIIT, high-intensity interval training; MOD, moderate-intensity continuous training; NR, not reported; SIT, sprint interval training.
Table 1 Continued
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and gynoid body composition.24 56 58 59 63 67–71 74 75 77 79–81 84–88 92 93
Others used bioelectrical impedance,57 64 65 78 89 91 hydroden-
sitometry,54 air displacement plethysmography60 83 or skinfold
measurements.61 62 66 72 76 90 Three studies used two body compo-
sition assessments methods, such as DXA and CT,87 bioelec-
trical impedance and CT,82 and bioelectrical impedance and
MRI.73 Online supplementary table S3 shows additional infor-
mation about body composition assessment methods used in the
included studies.
Quality assessment
A modified Downs and Black checklist30 assessment deter-
mined that the quality of studies had a mean score of 13.5±2.3
(ranging from 954 to 1970; online supplementary table S1). All
included studies specified their main findings and outcomes,
participant characteristics, statistical tests and accurate
measures. Only one study83 did not report variability esti-
mates. No studies blinded participants to exercise intervention,
and only eight (~20%) blinded assessors to group alloca-
tion.67 68 70 71 76 82 85 86 Most studies (~88%; n=36) randomised
participants to groups.24 54–58 60–64 66–71 73–76 78–82 84–93 Twenty-five
studies (~61%) reported adherence or compliance.56 59 61 62 64 67
68 70–72 74 76–78 80–86 88–90 93 Nineteen studies (~46%) adequately
reported adverse events.57 59–64 70–72 76 77 79 81 82 85 88 89 93 Four
studies (~10%) did not provide information about supervision
of exercise sessions.72 73 75 76
Meta-analysis
The within-group analysis found that interval training (−1.50
[95% CI −2.14 to −0.86, p=0.00001]) and MOD (−1.44
[95% CI −2.00 to −0.89, p<0.0001]) resulted in significant
improvements in total body fat percentage (%) (online supple-
mentary figures S1A and S2A, respectively). Significant improve-
ments also were found in total absolute fat mass (kg) for HIIT/
SIT (−1.58 [95% CI −2.74 to −0.43, p=0.007]) and MOD
(−1.13 [95% CI −2.18 to −0.08, p=0.04]) (online supplemen-
tary figures S1B and S2B, respectively).
Primary analysis
The between-group analyses on the effects of interval training
versus MOD on total body fat percentage (%) and total abso-
lute fat mass (kg) are presented in figure 2 and figure 3, respec-
tively. Overall, there was no difference between groups in total
body fat percentage (%) (p=0.705), with evidence of significant
heterogeneity in the meta-analysis of total body fat percentage
(%) (I2=75.4%, p<0.0001). However, there was a signifi-
cant difference between groups in total absolute fat mass (kg)
(p=0.0094), favouring interval training, with evidence of signif-
icant heterogeneity in the meta-analysis of total absolute fat mass
(kg) (I2=48.4%, p=0.0184).
Subgroup analyses demonstrated a significant effect of interval
training mode (SIT vs MOD), modality of exercise (walking/
jogging/running vs cycling), supervision (yes vs no), study quality
(low vs middle vs high), age (<30 vs ≥30 years) and interven-
tion duration (<12 vs ≥12 weeks) on total absolute fat mass (kg)
(online supplementary figures S3–S14); however, no significant
effect was found on total body fat percentage (%). No effect of
sex or BMI was observed on total absolute fat mass (kg) or total
body fat percentage (%) (online supplementary figures S15–
S18). Table 2 shows a synthesis of these results.
The mean duration of the HIIT, SIT and MOD proto-
cols included in the analyses of total body fat percentage (%)
were 28 min, 18 min and 38 min, respectively. The percentage
reductions of total body fat percentage (%) for these proto-
cols were, on average, 4.6%, 3.5% and 3.5%, respectively. On
average, HIIT, SIT and MOD protocols included in the analysis
on total absolute fat mass (kg) lasted 25 min, 23 min and 41 min,
respectively. The percentage reductions of total absolute fat mass
(kg) were, on average, 6.0%, 6.2% and 3.4%, respectively.
Sensitivity analyses and publication bias
A sensitivity analysis showed that a significant effect (p<0.05)
of HIIT/SIT on total absolute fat mass (kg) remained after
removal of each one of the included studies, with evidence of
significant heterogeneity (p<0.05). Funnel plots and Begg’s tests
for all analyses determined no indication of publication bias.
DISCUSSION
The present study analysed data from studies that compared
the effects of interval training and MOD on body adiposity in
humans. The analysis combined 41 studies (36 for meta-analysis)
involving a total of 1115 participants. Most studies included in
the meta-analysis (86.1%) involved a small sample size (<20
participants per intervention); therefore, the lack of statistical
power might have prevented the detection of between-group
differences in isolated studies. Notwithstanding, by pooling the
data, we did not find superiority of either interval training or
MOD in the reduction of total body fat percentage (%), as previ-
ously reported in an earlier meta-analysis.21 However, when
compared with MOD, we found a superiority of interval training
in the reduction of absolute total fat mass (kg). Indeed, both
interval training and MOD were similarly beneficial in eliciting
small improvements in total body fat percentage (%) (HIIT/SIT:
−1.50%; MOD: −1.44%) and in total absolute fat mass (kg)
(HIIT/SIT: −1.58 kg; MOD: −1.13 kg). However, a significant
difference was found between SIT and MOD in total absolute fat
mass (kg) (online supplementary figure S3B).
As a result of the sensitivity analysis that removed each
study one by one, we noted that the significant difference
favouring interval training for total absolute fat mass (kg) reduc-
tion remained. To better understand the factors that might influ-
ence the results, we critically reviewed individual studies that
favoured interval training or MOD. It is noteworthy that the
studies were selected based on their impact on our meta-analysis
and not necessarily the results reported in the article.
As for the data that supported MOD for a greater reduction
in total body fat percentage (%), the study by Buchan et al61 62
involved adolescents and started with four 30 s ‘all-out’ running
bouts interspaced by 30 s of rest, progressing to six bouts with
20 s of rest. This protocol, however, seems unfeasible, since the
recommended recovery between bouts in similar protocols is ~8
times the duration of the effort, such that 30 s maximum efforts
are usually followed by 4 min of rest.20 As such, it seems unlikely
the participants in the HIIT group in the study by Buchan et
al61 62 were able to maintain maximal effort across the exercise
bouts. Koubaa et al66 reported using running intervals of 2 min at
80% of v
V
O2max followed by 1 min of rest for interval training
in adolescents. However, they do not report information about
the number of bouts nor about rest intervals, which makes it
difficult to analyse the protocol. Moreover, neither Buchan et
al61 62 nor Koubaa et al66 provide data on dietary and physical
activity control.
Another study in favour of MOD is by Nybo et al,59 which
involved untrained men. During interval training, participants
were instructed to exceed 95% of the HRmax at the end of 2 min
of running and then rest for 2 min. However, considering that
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the intensity of effort was controlled only at the end of each
bout, it is not possible to be certain about the intensity of effort
maintained during each interval. If we consider that HR progres-
sively increases at a constant rate, it might be possible that the
participants spent most of the time at an intensity of effort lower
than recommended. Moreover, although the participants were
oriented to maintain their habitual lifestyle and dietary practices,
the authors did not control for this variable.
Some studies favoured interval training for per cent body fat
loss. Panissa et al90 used a 22 min protocol with 1 min at 90% and
30 s at 60% of HRmax. However, it seems again unfeasible for
participants to achieve the prescribed intensity of effort based on
the percentage of HRmax since both the times taken to increase
and decrease HR seem too short. For example, in the study of
Ramos et al,86 participants took 2 min to reach a similar inten-
sity of effort, and a previous study showed that HR decreases
~30 beats per minute in the first minute after intense exercise.94
The results of the study by Thomas et al54 also favoured interval
training for reductions in per cent body fat in a mixed sample of
men and women. MOD involved running for 3.2 or 6.4 km at
75% of HRmax, while interval training involved eight bouts of
running for 1 min at 90% HRmax followed by 3 min of walking.
However, a limitation of this study was the absence of diet and
physical activity control. Macpherson et al60 compared the
effects of SIT (4–6 ‘all-out’ efforts of 30 s in a manually driven
treadmill with 4 min of rest) and MOD (30–60 min running
at 60%
V
O2peak) in a mixed sample of physically active men
and women. Their data pointed towards greater decreases in
per cent body fat for SIT; however, while the authors reported
to have encouraged the participants to maintain their physical
activity and diet patterns, there were no objective measures of
these variables.
Figure 2 Main effects of HIIT/SIT versus MOD on total body fat (%). 4HIIT, high-intensity interval training (fourbouts); HIIT,high-intensity interval
training;MD, meanof differences;MOD, moderate-intensityinterval training; SIT,sprint interval training.
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These individual studies highlight the difficulty of drawing
general conclusions about the application and effects of interval
training on body composition. The inconsistent results might
be linked to factors such as habitual diet and physical activity
behaviours, since only 23 (~56%) and 19 (~46%) of the
included studies reported diet and physical activity control,
respectively. Another aspect that needs to be considered is the
quality of studies performing interval training and MOD. When
considering only the included studies with middle quality, inter-
vention duration less than 12 weeks or with participants’ age
less than 30 years, our results found a significant reduction in
absolute total fat mass (kg) favouring interval training, although
no significant difference was found on total body fat percentage
(%). This suggests an influence of the methodological quality of
the studies and participants’ characteristics on the results. More-
over, other aspects that might influence weight loss, such as
hormonal status,95 sleeping patterns96 and mood disorders,97 are
not usually analysed in these studies.
With regard to the factors inherent to interval training, the
absence of adequate control for supervision, intensity of effort
and the effort to rest ratio might be associated with at least some
of the inconsistent results. The subgroup meta-analysis demon-
strated that improvements in total absolute fat mass (kg) caused
by interval training are higher with supervision during interval
training protocols, providing evidence that supervision during
interval training is an important variable for total absolute
fat mass (kg) reduction. This might occur because it can help
interval training practitioners to train with higher intensity of
effort.98 Considering that supervision might guarantee adher-
ence to the prescribed protocol, the results provided by studies
with supervised sessions are probably more reliable. Therefore,
it is important that interval training studies consider providing
supervision to guarantee accountability.
In this sense, some examples of the inconsistency with regard
to the intensity of effort can be obtained from the analysis of
individual studies. For example, Keating et al70 reported that
their protocol was based on the study by Little et al,99 which
used 10 bouts of 60 s at a load that elicited 90% of HRmax inter-
spaced by 60 s of recovery. However, in the study by Keating et
al,70 HIIT was performed at 120% of i
V
O2max with 30–60 s
duration and 120–180 s of rest. On the other hand, at 120% of
i
V
O2max, a previous study used seven bouts of 30 s interspaced
with 15 s of rest.13
In addition, another interesting example of the possible influ-
ence of the control of intensity of effort on the results might
be found in Ramos et al.86 While the protocol was reported to
involve four bouts of 4 min at 85%–95% of HRpeak with 3 min
intervals, the participants took 2 min to reach the targeted inten-
sity. Therefore, the protocol seems to have involved 2 min of the
actual prescribed intensity of effort. In other words, the time at
target intensity of effort was not reached as planned, resulting
in a lower effort to rest ratio than intended. We would like to
note that these individual observations do not invalidate or ques-
tion the merit of previous studies. These are only some aspects
that might explain the large inconsistency among the results of
interval training and which we must consider when analysing
and reproducing previous studies.
Our results found that the effect of interval training proto-
cols when performed using walking/jogging/running modalities
on total absolute fat mass (kg) is greater than for MOD with
the same modalities. However, the number (n=5) of studies
included in this analysis was low,54 60 64 69 82 and only the study
by Zhang et al82 monitored and reported to control diet and
habitual activity. Moreover, our data also showed an influence of
exercise supervision, and a separate analysis showed that interval
training resulted in greater loss of total absolute fat mass (kg)
than MOD when training was supervised. Possibly, supervision
might influence accountability, influencing adherence to the
prescribed intensity of effort.98 Indeed, for other exercise modal-
ities, such as resistance training, supervision has been shown to
impact significantly on the intensity of effort and outcomes.98
Separate analyses with HIIT and SIT showed that ‘all-out’
SIT promotes greater total absolute fat mass (kg) reduction than
MOD. The greater decreases in fat loss promoted by SIT might
Figure 3 Main effects of HIIT/SIT versusMOD on total absolute fat mass (kg). HIIT, high-intensityinterval training; MD,mean of differences;MOD,
moderate-intensityinterval training; SIT,sprint interval training.
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be due to the increases in postexercise fat oxidation, which seems
to be associated with glycogen depletion.25 100 Indeed, vigorous
exercise may be mediated by a more pronounced increase in the
skeletal muscle oxidative capacity and by a sympathoadrenal
stimulation.101 Thus, protocols that rely more on the glycolytic
system might be more beneficial to body fat reductions.102 103
In general, although our findings suggest that MOD
provides similar benefits to interval training for total body fat
percentage (%) reduction, interval training might be an effi-
cacious, ‘time-efficient’ exercise strategy for body fat manage-
ment, since the MOD protocols examined in the included
studies usually had a greater duration than interval training
protocols and provide similar reductions in total body fat
percentage (%). For example, MOD protocols lasted on average
38 min (average of 35 sessions × 38 min/session=1330 min)
and provided a reduction of 3.5% in total body fat percentage
(%), while HIIT protocols lasted on average 28 min (average
of 33 sessions × 28 min/session=924 min) and provided
a reduction of 4.6%, and SIT protocols lasted on average
18 min (average of 29 sessions × 18 min/session=526 min)
and provided a reduction of 3.5% in total body fat percentage
(%). In other words, MOD protocols provided a reduction
of ‘0.0026% per minute’, while HIIT and SIT protocols
provided a reduction of ‘0.0050% and 0.0067% per minute’
in total body fat percentage (%), respectively. The analysis
showed that interval training promotes greater reductions in
total absolute fat mass (kg) than MOD, despite requiring less
time to be performed. However, it is important to be aware of
the possible risks and caveats associated with higher intensity
training. For example, it might increase the risk of injury and
impose higher cardiovascular stress. Adherence should also be
examined, as higher intensity protocols can result in higher
discomfort.
Table 2 Summary of HIIT/SIT versusMOD subgroup meta-analysis on body composition
Outcome (subgroup)
Between-group effects
Studies (n) MD (95% CI) P value
Heterogeneity
I2(%) P value
Total body fat (%)
Mode:HIIT 23 −0.35 (−1.90 to 1.21) 0.66 78 <0.01
Mode:SIT 13 −0.04 (−2.02 to 1.94) 0.97 71 <0.01
Modality:walking/jogging/running 14 −1.03 (−1.33 to 3.38) 0.39 86 <0.01
Modality:cycling 16 −0.88 (−1.93 to 0.17) 0.10 26 0.16
Sex:male 10 0.86 (−1.36 to 3.07) 0.45 65 <0.01
Sex:female 9 −1.36 (−3.85 to 1.14) 0.29 89 <0.01
Age<30 years 19 −0.23 (−2.08 to 1.62) 0.81 86 <0.01
Age≥30 years 16 0.15 (−0.94 to 1.23) 0.79 0 0.92
BMI<30 kg/m218 −0.81 (−2.54 to 0.93) 0.36 70 <0.01
BMI≥30 kg/m210 1.15 (−0.98 to 3.28) 0.29 77 <0.01
Study quality:low 12 0.44 (−2.11 to 2.98) 0.74 85 <0.01
Study quality:middle 16 −0.52 (−2.29 to 1.26) 0.57 67 <0.01
Study quality:high 8 −0.89 (−2.13 to 0.36) 0.16 0 0.96
Intervention duration<12 months 15 −0.03 (−2.11 to 2.05) 0.98 84 <0.01
Intervention duration≥12 months 21 −0.38 (−1.66 to 0.91) 0.56 53 <0.01
Supervision:yes 26 −0.71 (−1.85 to 0.44) 0.23 59 <0.01
Supervision:no 10 1.06 (−1.60 to 3.72) 0.43 80 <0.01
Total fat mass (kg)
Mode:HIIT 10 −1.96 (−4.19 to 0.26) 0.08 56 0.02
Mode:SIT 5 −3.22 (−5.71 to−0.73) 0.01 18 0.30
Modality:walking/jogging/running 5 −5.18 (−8.73 to−1.63) <0.01 67 0.02
Modality:cycling 9 −1.17 (−2.64 to 0.29) 0.12 0 0.51
Sex:male 2 −0.14 (−3.62 to 3.34) 0.94 0 0.37
Sex:female 6 −1.23 (−2.83 to 0.38) 0.14 0 0.51
Age<30 years 8 −3.92 (−6.36 to−1.49) <0.01 63 <0.01
Age≥30 years 7 0.19 (−1.94 to 2.32) 0.86 0 0.85
BMI<30 kg/m28 −1.36 (−3.03 to 0.26) 0.10 0 0.54
BMI≥30 kg/m23 −2.75 (−5.77 to 0.27) 0.08 0 0.79
Study quality:low 2 −5.59 (−21.03 to 9.85) 0.48 91 <0.01
Study quality:middle 10 −2.03 (−3.60 to −0.47) 0.01 12 0.33
Study quality:high 3 −1.10 (−3.73 to 1.54) 0.42 20 0.29
Intervention duration<12 months 7 −2.82 (−4.79 to−0.84)] <0.01 16 0.31
Intervention duration≥12 months 8 −1.88 (−4.67 to 0.90) 0.19 62 <0.01
Supervision:yes 14 −2.21 (−4.03 to 0.38) 0.02 51 0.01
Supervision:no 1 – –
Significant p values are indicated in bold.
BMI, body mass index; HIIT, high-intensity interval training; MD, mean of differences; MOD, moderate-intensity continuous training; SIT, sprint interval training.
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A common criticism of meta-analysis is the combination of
largely heterogeneous studies that have important method-
ological differences, which can influence the reported effects
particularly when the number of included studies is low.104 105
According to Grindem et al,106 heterogeneity is a key factor in
the decision to pool or not to pool the results of available studies,
which makes it a challenging issue in systematic reviews. The
included studies presented relatively high heterogeneity in the
total meta-analysis of total body fat percentage (%) and total
absolute fat mass (kg), and this may be a reflection of the large
heterogeneity in exercise protocols used in the included studies.
Broadly speaking, the different protocols (HIIT/SIT or MOD)
seem similarly effective in modulating body adiposity in humans;
however, the varied approaches used make it difficult to draw
general conclusions and recommendations about the ‘ideal’
interval training or MOD protocol. Therefore, clinicians must
be careful when interpreting these results and applying them
to their practice. Future studies must improve their method-
ological quality, sample size and method of assessment of change
in total body fat to provide more compelling evidence in favour
of a specific protocol, or to elucidate the principles of protocol
design that appear to have the greatest influence on outcomes.
CONCLUSION
The present systematic review with meta-analysis showed that
interval training provides benefits similar to MOD in total body
fat percentage (%) reduction; however, interval training provided
a greater total absolute fat mass (kg) reduction than MOD. SIT
resulted in greater total absolute fat loss when compared with
MOD. A number of factors may positively influence the effects
of interval training on total absolute fat mass, including super-
vision of exercise, walking/running/jogging as the exercise of
choice, age (<30 years), study quality and intervention duration
(<12 weeks). In general, our findings suggest that the ‘signal in
the noise’ is the similar effects of interval training and MOD on
total body fat percentage (%) management and the superiority
of interval training for total absolute fat mass (kg) reduction, yet
that these effects can be produced in a ‘time-efficient’ manner
when using interval training.
Contributors RBV and JPAN carried out the screenings and reviews. RBV and
VSC carried out the analysis of the articles. RBV and PG drafted and revised the
manuscript. CABdL, VSC, JS, JPF and PG revised the manuscript. All authors read and
approved the final manuscript.
Funding This research did not receive any specific grant from funding agencies in
the public, commercial, or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
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What is already known
Physical activity may be a useful tool to reduce body
adiposity; however, many people fail to adhere to exercise
programmes due to lack of time or lack of results.
Interval training is an attractive alternative to address
overweight and obesity given its potential to offer
benefitssimilar to moderate-intensity continuous training
while requiring less time.
There are currently many different approaches to performing
interval training, yet there is no consensus as to which
training method or protocol is ‘best’ for reducing body
adiposity.
What are the new findings
Interval training and moderate-intensity continuous training
provide similar benefits for body fat percentage reduction;
however, interval training provides greater reductions in total
absolute fat mass.
Supervision, walking/running/jogging, age, study quality
and intervention duration seem to favourably influence the
decreases in body adiposity observed from interval training
programmes.
There is great methodological diversity among interval
training protocols in the literature, which makes it difficult to
generally recommend that one particular protocol is ‘best’ for
modulating body adiposity in humans.
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... HIIT exercise is an explosive, rapid, and full exercise in a short period of time, which increases the body's demand for oxygen and creates a hypoxic state, and which increases the patient's cardiac pumping function and improves cardiopulmonary exchange function; in addition, the increase in exercise stimulation can better improve their cardiovascular fitness and exercise capacity, thereby promoting the outcome of the disease and improving the quality of life [22][23][24][25]. However, MCT exercise also has some limitations, which are more suitable for patients who cannot tolerate high-intensity training [26][27][28][29]. Clinical studies have found that cardiovascular diseases can bring physical pain or discomfort to patients [30], limit the patient's normal work and life, and easily cause patients to have negative psychology such as anxiety and depression. ...
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Background: Cardiovascular disease is a common disease with high prevalence, disability, and mortality. Exercise therapy can improve cardiac functional reserve and life quality of patients, but the benefits of different exercise intensities for cardiovascular patients are still controversial. In this study, literature search and meta-analysis were used to explore the effect of 2 intensities of exercise on the rehabilitation effect of cardiovascular patients. Methods: We searched Embase, Wiley online library, PubMed, Science Direct, and Clinicaltrials to look for randomized controlled trial (RCT) studies of high-intensity interval training (HIIT) versus moderate continuous training (MCT). After screening the inclusion criteria for the literature and assessing the risk of bias, a software analysis was performed using the R language toolkit to obtain forest plots and funnel maps. Results: 10 articles were included in this study into the quantitative analysis, and 520 patients participated in the study; meta-analysis results showed that after HIIT intervention, the VO2 peak index of patients was higher than that of the MCT group (MD = 1.39, 95% CI (0.10, 2.68), Z = 2.12, P = 0.0344), the peak heart rate HR peak was higher than that of the MCT training (MD = 7.71, 95% CI (5.12, 10.30), Z = 5.84, P < 0.0001), the respiratory exchange rate (maximum RER) was higher than that of the MCT training (MD = 0.02, 95% CI (0.00, 0.04), Z = 2.36, P = 0.0184), and the quality of life was higher than that of the MCT training (MD = 0.39, 95% CI (0.07, 0.71), Z = 2.40, P = 0.0165). Discussion. Compared with moderate continuous training, high intensity interval training is more conducive to improve the cardiopulmonary function of cardiovascular patients and improve their physical life quality.
... Weight loss is also a key issue in the management of T2DM. Despite finding of a superior benefit on weight loss after HIIT intervention compared with MICT being not well established, a recent meta-analysis has reported that HIIT provided 28.5% greater reductions in total absolute fat mass than MICT [61]. Our meta-analysis revealed no significant decreases in BMI after HIIT intervention compared with control or MICT groups. ...
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Aim: The objective of this meta-analysis was to explore the effects of high-intensity interval training (HIIT) compared with control conditions (CON) or moderate intensity continuous training (MICT) on glycemic parameters in diabetes subjects. Methods: Pubmed, Embase and Google Scholar databases were searched for HIIT interventions that were carried out in diabetic subjects and exploring fasting glucose, glycated haemoglobin (HbA1c), fasting insulin and/or HOMA-IR. Results: This systematic review retrieved a total of 1741 studies of which 32 articles fulfilled the eligibility criteria. Nineteen trials were included in the meta-analysis since they compared HIIT intervention with CON or MICT group. There was a significantly reduction of fasting glucose of 13.3 mg/dL(p<0.001), Hb1Ac -0.34% (p<0.001), insulin -2.27 UI/L (p=0.003), HOMA-IR -0.88 (p=0.005) in the HIIT-group compared with CON-group. Nevertheless, this reduction was not significantly different when comparing HIIT with MICT (p= 0.140, p=0.315, p=0.520 and p=0.389). Besides, there was a significant increase of absolute VO2max of 0.21 L/min (p<0.001) and relative VO2max of 2.94 ml/kg/min (p<0.001) in the HIIT-group compared with the CON-group and the MICT-group (0.22 L/min, p=0.025) and (0.97 ml/kg/min, p=0.045). Conclusions: These findings revealed that HIIT intervention led to significant improvement in glycemic control and insulin resistance in subjects with diabetes compared with CON-group.
... Research has shown that HIIT can evoke beneficial effects on cardiometabolic risk indices in overweight and obese populations after only a few weeks (19). Additionally, it has been demonstrated that HIIT provides similar or even superior effects for reducing body fat mass than MICT (20). Data on the effects of HIIT on NAFLD are still very limited but initial studies (21)(22)(23)(24)(25)(26), including a first meta-analysis (27), have revealed beneficial impact on intrahepatic fat (IHF) levels. ...
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Non-alcoholic fatty liver disease (NAFLD) and cardiometabolic disorders are highly prevalent in obese individuals. Physical exercise is an important element in obesity and metabolic syndrome (MetS) treatment. However, the vast majority of individuals with obesity do not meet the general physical activity recommendations (i.e. 150 min of moderate activity per week). The present study aimed to investigate the impact of a highly time-saving high-intensity interval training (HIIT) protocol (28 min time requirement per week) on NAFLD fibrosis (NFS) and cardiometabolic risk scores in obese patients with MetS and elevated NFS values. Twenty-nine patients performed HIIT on cycle ergometers (5 x 1 min at an intensity of 80 - 95% maximal heart rate) twice weekly for 12 weeks and were compared to a control group without exercise (CON, n = 17). Nutritional counseling for weight loss was provided to both groups. NFS, cardiometabolic risk indices, MetS z-score, cardiorespiratory fitness (VO2max) and body composition were assessed before and after intervention. The HIIT (-4.3 kg, P < 0.001) and CON (-2.3 kg, P = 0.003) group significantly reduced body weight. There were no significant group differences in relative weight reduction (HIIT: -3.5%, CON: -2.4%). However, only the HIIT group improved NFS (-0.52 units, P = 0.003), MetS z-score (-2.0 units, P < 0.001), glycemic control (HbA1c: -0.20%, P = 0.014) and VO2max (+3.1 mL/kg/min, P < 0.001). Decreases in NFS (-0.50 units, P = 0.025) and MetS z-score (-1.4 units, P = 0.007) and the increment in VO2max (3.3 mL/kg/min, P < 0.001) were significantly larger in the HIIT than in the CON group. In conclusion, only 28 min of HIIT per week can elicit significant improvements in NFS and a several cardiometabolic health indices in obese MetS patients with increased NFS grades. Our results underscore the importance of exercise in NAFLD and MetS treatment and suggest that our low-volume HIIT protocol can be regarded as viable alternative to more time-consuming exercise programs.
... These findings suggested that it took over 1 month for HIIT + fasting to improve body mass and BMI, which could become a guideline of HIIT + fasting in clinical application. Our finding showed that compared to the control group, HIIT + fasting had no significant effects on PFM, which is similar to Viana et al. [54] whose meta-analysis that combined 24 studies revealed that different interventions had almost no differences in the improvement of PFM. The combination of the different interventions seemed to have little clinical significance on PFM reduction. ...
Article
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Objectives: A systematic review and meta-analysis is conducted to compare the effects of high-intensity interval training (HIIT) combined with fasting (HIIT + fasting) and other interventions (HIIT alone, fasting alone, or normal intervention) in adults with overweight and obesity on body composition (body mass, body mass index (BMI), waist circumference (WC), percent fat mass (PFM), fat mass (FM), fat-free mass (FFM)), maximal oxygen uptake (VO2peak), and glucose metabolism (fasting plasma glucose (FPG)), fasting plasma insulin (FPI)). Methods: The databases of PubMed, the Cochrane Library, Embace, Web of Science, CNKI, Wangfang Data, and CBM were searched from their inception to February 2022. Randomized controlled trials comparing the effects of HIIT + fasting and other interventions on adults with overweight and obesity were included in this meta-analysis. The risk of bias was assessed by the Cochrane risk of bias tool. The effect size was completed by using mean difference (MD) and standard deviation. If there were varying units or large differences among the included studies, the standardized mean difference (SMD) would be used. The certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Results: Nine randomized controlled trials with 230 overweight and obese adults were conducted in accordance with our inclusion criteria. The results of the meta-analysis revealed that compared to the control group HIIT + fasting had better effects on the body mass, WC, FM, and VO2peak, while there were no significant differences in PFM, FFM, FPG, and FPI. Conclusions: Despite the number of included trials being small and the GRADE of all outcomes being very low, HIIT + fasting has a positive effect on the body composition of overweight and obese adults, and significantly improves VO2peak. For adults with overweight and obesity who have long-term comorbidity, HIIT + fasting was a better way to improve FPG than HIIT alone or fasting alone. More studies are required to investigate different combinations of HIIT + fasting; and the safety of HIIT + fasting intervention on overweight and obese adults.
... In recent years, there has been a growing interest in studying the different impacts of HIIT and MICT exercise modalities on energy expenditure and the metabolism of lipid oxidation in obesity [7,18,29,35]. Here, in an experimental model, we demonstrated HFD-induced hepatic lipid accumulation Table 2 Changes in serum lipid and inflammatory markers in rats of each group LC, lean + quiet control group; LHI, lean + high-intensity interval exercise training group; LMI, lean + moderated intensity continuous training group; OC, obesity + quiet control group; OHI, obesity + high-intensity interval exercise training group; OMI, obesity + moderated intensity continuous training group; TG, triglycerides; Ch, cholesterin; LDL-C, low-density lipoprotein cholesterin; MCP-1, monocyte chemotactic protein 1; IL-1β, interleukin-1 β; TNF-α, tumor necrosis factor alpha. ...
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Background Obesity in children has become one of the key concerns of the World Health Organization, and the incidence of related non-communicable diseases is also rising. This study evaluates the effect of family sports participation on the treatment and prevention of obesity in children aged 0–14 years by systematic analysis. Method A literature review from 2000 to 2020 was conducted. According to PRISMA-IPD (Preferred Reporting Items for MetaAnalyses of individual participant data) guidelines. The two researchers independently assessed the risk and bias of the articles, obtained a comprehensive, high-quality result, and extracted the data based on the Cochrane intervention system review manual. Randomized controlled trials (RCTs) were selected from the searches that used family sports interventions or family sports combined with dietary adjustments and behavioral habits change. Only studies targeting overweight or obese children aged 0–14 years were included. Results The search resulted in a total of 16 studies. Across all 16 studies, there were a total of 1680 participants in the experimental groups and 1701 participants in the control groups. The results are as follows: body mass index ( BMI ) (SMD-RE = − 4.10, 95% CI (− 0.84 to 0.02), Z = 1.88, p = 0.06); Body weight (SMD-RE = − 0.77, 95% CI (− 1.53 to − 0.01), Z = 2.00, p = 0.05); Waist circumference (SMD-RE = − 0.45, 95% CI (− 1.36 to 0.47), Z = 0.96, p = 0.34); and Body fat rate (SMD-FE = − 0.06, 95% CI (− 0.22 to 0.11), Z = 0.69, p = 0.49). Hence, through family sports intervention among obese children, juvenile and obese body composition—BMI, body weight, waist circumference, and body fat rate—are all reduced. But only body weight was statistically significant. Conclusions Compared with the samples without family sports, the weight of obese children participating in family sports decreased, but there were no significant differences in other relevant physical indicators. Follow-up research should examine large-scale clinical trials with family sports as a single factor intervention, which are needed to provide stronger evidence of the intervention effect. However, family activities can help obese children grow and develop by improving their exercise capacity, enhancing their lifestyles, and facilitating communication and relationships with their parents. In the future, long-term sports training plans for children with obesity should be implemented.
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Background Performing multiple high-intensity interval training (HIIT) sessions in a compressed period of time (approximately 7–14 days) is called a HIIT shock microcycle (SM) and promises a rapid increase in endurance performance. However, the efficacy of HIIT-SM, as well as knowledge about optimal training volumes during a SM in the endurance-trained population have not been adequately investigated. This study aims to examine the effects of two different types of HIIT-SM (with or without additional low-intensity training (LIT)) compared to a control group (CG) on key endurance performance variables. Moreover, participants are closely monitored for stress, fatigue, recovery, and sleep before, during and after the intervention using innovative biomarkers, questionnaires, and wearable devices. Methods This is a study protocol of a randomized controlled trial that includes the results of a pilot participant. Thirty-six endurance trained athletes will be recruited and randomly assigned to either a HIIT-SM (HSM) group, HIIT-SM with additional LIT (HSM + LIT) group or a CG. All participants will be monitored before (9 days), during (7 days), and after (14 days) a 7-day intervention, for a total of 30 days. Participants in both intervention groups will complete 10 HIIT sessions over 7 consecutive days, with an additional 30 min of LIT in the HSM + LIT group. HIIT sessions consist of aerobic HIIT, i.e., 5 × 4 min at 90–95% of maximal heart rate interspersed by recovery periods of 2.5 min. To determine the effects of the intervention, physiological exercise testing, and a 5 km time trial will be conducted before and after the intervention. Results The feasibility study indicates good adherence and performance improvement of the pilot participant. Load monitoring tools, i.e., biomarkers and questionnaires showed increased values during the intervention period, indicating sensitive variables. Conclusion This study will be the first to examine the effects of different total training volumes of HIIT-SM, especially the combination of LIT and HIIT in the HSM + LIT group. In addition, different assessments to monitor the athletes' load during such an exhaustive training period will allow the identification of load monitoring tools such as innovative biomarkers, questionnaires, and wearable technology. Trial Registration : clinicaltrials.gov, NCT05067426. Registered 05 October 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05067426 . Protocol Version Issue date: 1 Dec 2021. Original protocol. Authors: TLS, NH.
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Purpose. Obesity is currently a serious, worldwide public health problem and a lifelong disease requiring early intervention before adulthood .This study compares the effects of high intensity aerobic training (HIAT) and Moderate intensity aerobic training (MIAT) after four and eight weeks on body composition in girls’ obese students. Methods. The present study includes 21 obese female students (fat percent 36% and BMI: 29.6%) randomly placed in three same groups, HIAT (n =7), MIAT (n =7) and control (n =6). Body composition (weight, body mass index, fat percentage, body fat mass, lean body mass and waist to hip ratio) in the students was measured using Bioimpedance before, in the middle and after 8 weeks of exercise. The exercises were done three days a week with interval high intensity (85-95% HR peak) and continuous moderate intensity (50 -70 % HR peak) respectively for 33 and 41 minutes with the same energy expenditure on the treadmill. To data analysis, parametric methods were used (t - paired and ANOVA) at significance level of α=0.05. Results. Results showed that although HIAT reduced the mentioned items in body composition in each of the testing processes, but this reduction was not significant, while the MIAT significantly decreased fat percentage, fat mass and WHR after 8 weeks. It also reduced other items except body lean mass but, they were non-significant. The significant difference was observed in body fat mass and fat percentage after 8 weeks between MIAT and HIAT. Comparing MIAT and control groups showed that significant difference in fat mass after 4 and 8 weeks and in fat percentage after 8 weeks. Conclusions. Research results indicates that the MIAT causes further changes in body composition compared to the HIAT, although, during activity, HIAT fat oxidation rate was significantly improved after 8 weeks. Key words. Aerobic training, Body composition, Intensity, Obesity
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Interval training (IT) has been used for many decades with the purpose to increase performance and promote health benefits while demanding a relatively small amount of time. IT can be defined as intermittent periods of intense exercise separated by periods of recovery and has been divided into high-intensity interval training (HIIT), sprint interval training (SIT) and repeated sprint training (RST). IT use resulted in the publication of many studies and many of them with conflicting results and positions. The aim of this article was to move forward and understand studies’ protocol in order to draw accurate conclusions, as well as to avoid previous mistakes and effectively reproduce previous protocols. When analyzing the literature, we found many inconsistencies, such as, the controversial concept of ‘supramaximal’ effort, a misunderstanding regarding the term ‘high intensity’ and the use of different strategies to control intensity. The adequate definition and interpretation of training intensity seems to be vital, since the results of IT are largely dependent on it. These observations are only a few examples of the complexity involved with IT prescription, discussed to illustrate some problems with the current literature regarding IT. Therefore, it is our opinion that it is not possible to draw general conclusions about IT without considering all variables used in IT prescription, such as, exercise modality, intensity, effort andrest times and participants’ characteristics. In order to help guide researchers and health professionals in their practices it is important that experimental studies report their methods in as much detail as possible and future reviews and meta-analyses should critically discuss the articles included in light of their methods to avoid inadequate generalizations.
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Background: High-intensity interval training (HIIT) has been shown to improve cardiometabolic health during supervised lab-based studies but adherence, enjoyment, and health benefits of HIIT performed independently are yet to be understood. We compared adherence, enjoyment, and cardiometabolic outcomes after 8 weeks of HIIT or moderate-intensity continuous training (MICT), matched for energy expenditure, in overweight and obese young adults. Methods: 17 adults were randomized to HIIT or MICT. After completing 12 sessions of supervised training over 3 weeks, participants were asked to independently perform HIIT or MICT for 30 min, 4 times/week for 5 weeks. Cardiometabolic outcomes included cardiorespiratory fitness (VO2 peak), lipids, and inflammatory markers. Exercise enjoyment was measured by the validated Physical Activity Enjoyment Scale. Results: Exercise adherence (93.4 ± 3.1% vs. 93.1 ± 3.7%, respectively) and mean enjoyment across the intervention (100.1 ± 4.3 vs. 100.3 ± 4.4, respectively) were high, with no differences between HIIT and MICT (p > .05). Similarly, enjoyment levels did not change over time in either group (p > .05). After training, HIIT exhibited a greater decrease in low-density lipoprotein cholesterol than MICT (-0.66 mmol L(-1) vs. -0.03 mmol L(-1), respectively) and a greater increase in VO2 peak than MICT (p < .05, +2.6 mL kg min(-1) vs. +0.4 mL kg min(-1), respectively). Interleukin-6 and C-reactive protein increased in HIIT (+0.5 pg mL(-1) and + 31.4 nmol L(-1), respectively) and decreased in MICT (-0.6 pg mL(-1) and -6.7 nmol L(-1), respectively, p < .05). Conclusions: Our novel findings suggest that HIIT is enjoyable and has high unsupervised adherence rates in overweight and obese adults. However, HIIT may be associated with an increase in inflammation with short-term exercise in this population.
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Purpose: The purpose of this randomized controlled trial was to compare the effect of all-extremity high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on aortic pulse wave velocity (PWV) and carotid artery compliance in older adults. Methods: Forty-nine sedentary older adults (age: 64±1 years), free of overt major clinical disease, were randomized to HIIT (n=17), MICT (n=18) or non-exercise controls (CONT; n=14). HIIT (4x4 minutes at 90% of peak heart rate interspersed with 3x3 minutes active recovery at 70% of peak heart rate) and isocaloric MICT (70% of peak heart rate) were performed on an all-extremity non-weight-bearing ergometer, 4 days/week, for 8 weeks under supervision. Aortic (carotid to femoral; cfPWV) and common carotid artery compliance were assessed at pre- and post-intervention. Results: cfPWV improved by 0.5 m/sec in MICT (P=0.04), but did not significantly change in HIIT and CONT (P>0.05). Carotid artery compliance improved by 0.03 mm/mmHg in MICT (P=0.001), while it remained unchanged in HIIT and CONT (P>0.05). Improvements in arterial stiffness in response to MICT were not confounded by changes in aortic or brachial blood pressure, heart rate, body weight, total and abdominal adiposity, blood lipids or aerobic fitness. Conclusion: All-extremity MICT, but not HIIT, improved central arterial stiffness in previously sedentary older adults free of major clinical disease. Our findings have important implications for aerobic exercise prescription in older adults.
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PurposeIt remains to be established how high-intensity aerobic interval training (HAIT) affects risk factors associated with type 2 diabetes (TD2). This study investigated effects of HAIT on maximal oxygen uptake (VO2max), glycated Hemoglobin type A1C (HbA1c), insulin resistance (IR), fat oxidation (FatOx), body weight (BW), percent body fat (%BF), lactate threshold (LT), blood pressure (BP), and blood lipid profile (BLP) among persons with T2D. Results were compared to the effects after a moderate-intensity training (MIT) program. Methods Thirty-eight individuals with T2D completed 12 weeks of supervised training. HAIT consisted of 4 × 4 min of walking or running uphill at 85–95% of maximal heart rate, and MIT consisted of continuous walking at 70–75% of maximal heart rate. ResultsA 21% increase in VO2max (from 25.6 to 30.9 ml kg−1 min−1, p < 0.001), and a reduction in HbA1c by −0.58% points (from 7.78 to 7.20%, p < 0.001) was found in HAIT. BW and body mass index (BMI) was reduced by 1.9% (p < 0.01). There was a tendency towards an improved FatOx at 60% VO2max (14%, p = 0.065). These improvements were significant different from MIT. Both HAIT and MIT increased velocity at LT, and reduced %BF, waist circumference, hip circumference, and BP, with no significant differences between the two groups. Correlations were found between change in VO2max and change in HbA1c when the two intervention groups were combined (R = −0.52, p < 0.01). ConclusionHAIT is an effective exercise strategy to improve aerobic fitness and reduce risk factors associated with T2D.
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This study compared the effect of prolonged moderate-intensity continuous training (MICT) on reducing abdominal visceral fat in obese young women with that of work-equivalent (300 kJ/training session) high-intensity interval training (HIIT). Forty-three participants received either HIIT ( n=15 ), MICT ( n=15 ), or no training (CON, n=13 ) for 12 weeks. The abdominal visceral fat area (AVFA) and abdominal subcutaneous fat area (ASFA) of the participants were measured through computed tomography scans preintervention and postintervention. Total fat mass and the fat mass of the android, gynoid, and trunk regions were assessed through dual-energy X-ray absorptiometry. Following HIIT and MICT, comparable reductions in AVFA (−9.1, −9.2 cm ² ), ASFA (−35, −28.3 cm ² ), and combined AVFA and ASFA (−44.7, −37.5 cm ² , p>0.05 ) were observed. Similarly, reductions in fat percentage (−2.5%, −2.4%), total fat mass (−2.8, −2.8 kg), and fat mass of the android (−0.3, −0.3 kg), gynoid (−0.5, −0.7 kg), and trunk (−1.6, −1.2 kg, p>0.05 ) regions did not differ between HIIT and MICT. No variable changed in CON. In conclusion, MICT consisting of prolonged sessions has no quantitative advantage, compared with that resulting from HIIT, in abdominal visceral fat reduction. HIIT appears to be the predominant strategy for controlling obesity because of its time efficiency.
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Objectives Apelin is an adipokine that is related to regulation of glucose homeostasis and disorders caused by obesity. However, few studies have addressed the effects of exercise in along with caloric restriction on plasma apelin. The purpose of this study was to investigate the impact of different types of exercise along with caloric restriction on plasma apelin 36, TNF-α, and insulin resistance. Material and methods Forty volunteer subjects were randomly divided into four groups: caloric restriction (n = 8) with 500 kcal/d; caloric restriction with high-intensity interval training (n = 10) (6–12 × 1 min intervals running on a treadmill at 90–95% maximal heart rate with 1 min of active rest between the intervals); caloric restriction with continuous training (walking/jogging at 65–70% maximal heart rate) (n = 12); and caloric restriction with resistance training (60–80% one-repetition maximum (1RM)) (n = 10). The protocols were isocaloric. Results Body weight, fat percent, and body mass index (BMI) significantly decreased in all groups (P < 0.001 for all four groups). Plasma levels of apelin 36 significantly decreased in all groups (P < 0.01), while homeostatic model assessment-insulin resistance (HOMA-IR) significantly improved (P < 0.01). There was no significant difference between groups. Only combination of caloric restriction with high-intensity interval training induced a significant reduction in TNF-α levels (P < 0.05). Conclusion Isocaloric interventions (exercise and nutritional) similarly decreased plasma apelin 36 levels and HOMA-IR in overweight men, whereas plasma levels of TNF-α are a function of exercise intensity.