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Background This systematic review and meta-analysis summarized the most recent evidence on the efficacy of intermittent energy restriction (IER) versus continuous energy restriction on weight-loss, body composition, blood pressure and other cardiometabolic risk factors. Methods Randomized controlled trials were systematically searched from MEDLINE, Cochrane Library, TRIP databases, EMBASE and CINAHL until May 2018. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Results Eleven trials were included (duration range 8–24 weeks). All selected intermittent regimens provided ≤ 25% of daily energy needs on “fast” days but differed for type of regimen (5:2 or other regimens) and/or dietary instructions given on the “feed” days (ad libitum energy versus balanced energy consumption). The intermittent approach determined a comparable weight-loss (WMD: − 0.61 kg; 95% CI − 1.70 to 0.47; p = 0.87) or percent weight loss (WMD: − 0.38%, − 1.16 to 0.40; p = 0.34) when compared to the continuous approach. A slight reduction in fasting insulin concentrations was evident with IER regimens (WMD = − 0.89 µU/mL; − 1.56 to − 0.22; p = 0.009), but the clinical relevance of this result is uncertain. No between-arms differences in the other variables were found. Conclusions Both intermittent and continuous energy restriction achieved a comparable effect in promoting weight-loss and metabolic improvements. Long-term trials are needed to draw definitive conclusions. Electronic supplementary material The online version of this article (10.1186/s12967-018-1748-4) contains supplementary material, which is available to authorized users.
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Cioetal. J Transl Med (2018) 16:371
https://doi.org/10.1186/s12967-018-1748-4
REVIEW
Intermittent versuscontinuous energy
restriction onweight loss andcardiometabolic
outcomes: asystematic review
andmeta-analysis ofrandomized controlled
trials
Iolanda Cioffi1, Andrea Evangelista2, Valentina Ponzo3, Giovannino Ciccone2, Laura Soldati4, Lidia Santarpia1,
Franco Contaldo1, Fabrizio Pasanisi1, Ezio Ghigo3 and Simona Bo3*
Abstract
Background: This systematic review and meta-analysis summarized the most recent evidence on the efficacy of
intermittent energy restriction (IER) versus continuous energy restriction on weight-loss, body composition, blood
pressure and other cardiometabolic risk factors.
Methods: Randomized controlled trials were systematically searched from MEDLINE, Cochrane Library, TRIP data-
bases, EMBASE and CINAHL until May 2018. Effect sizes were expressed as weighted mean difference (WMD) and 95%
confidence intervals (CI).
Results: Eleven trials were included (duration range 8–24 weeks). All selected intermittent regimens provided 25%
of daily energy needs on “fast” days but differed for type of regimen (5:2 or other regimens) and/or dietary instructions
given on the “feed” days (ad libitum energy versus balanced energy consumption). The intermittent approach deter-
mined a comparable weight-loss (WMD: 0.61 kg; 95% CI 1.70 to 0.47; p = 0.87) or percent weight loss (WMD:
0.38%, 1.16 to 0.40; p = 0.34) when compared to the continuous approach. A slight reduction in fasting insulin
concentrations was evident with IER regimens (WMD = 0.89 µU/mL; 1.56 to 0.22; p = 0.009), but the clinical
relevance of this result is uncertain. No between-arms differences in the other variables were found.
Conclusions: Both intermittent and continuous energy restriction achieved a comparable effect in promoting
weight-loss and metabolic improvements. Long-term trials are needed to draw definitive conclusions.
Keywords: Continuous energy restriction, Intermittent energy restriction, Fasting glucose, Triglycerides, Weight loss
© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
(http://creat iveco mmons .org/licen ses/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://creat iveco mmons .org/
publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Background
In the last decade, much interest has been focused on
dietary strategies that manipulate energy intake uncon-
ventionally, known as intermittent fasting or intermit-
tent energy restriction (IER) [14]. is dietary approach
has gained greater attention and popularity as a way for
losing weight alternative to the conventional weight-loss
diets, characterized by continuous (non-intermittent)
energy restriction (CER). e two most popular forms
of IER are: the 5:2 diet characterized by two consecu-
tive or non-consecutive “fast” days and the alternate-day
energy restriction, commonly called alternate-day fast-
ing, alternate-day modified fasting, or every-other-day
fasting, consisting of a ‘‘fast” day alternated with a ‘‘feed”
day [5]. Commonly, during “fast” days, the energy intake
is severely restricted, ranging from complete abstinence
Open Access
Journal of
Translational Medicine
*Correspondence: simona.bo@unito.it
3 Department of Medical Sciences, University of Turin, c.so AM Dogliotti
14, 10126 Turin, Italy
Full list of author information is available at the end of the article
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Cioetal. J Transl Med (2018) 16:371
from foods to a daily maximum intake roughly corre-
sponding to 75% energy restriction. erefore, the term
“fast” often does not involve a true complete abstinence
from caloric intake. e term IER will be used to describe
all intermittent energy-restricted/fasting regimens.
e time-restricted feeding [2, 69] and the very-low-
calorie or energy diets [2, 3] are other types of dietary
interventions which were often included in previous sys-
tematic reviews and meta-analyses on IER. Indeed, in the
former, individuals are allowed to eat within a specific
range of time, thus, every day there is a period without
food intake, varying from 12 to 21 h [1012] (i.e. the
Muslim Ramadan). On the other hand, there is no daily
intermittency in a very-low-calorie-diet, although the
overall energy intake may be similar to those of the IER
regimens [13].
To the best of our knowledge, an overall evaluation of
the impact of IER on multiple metabolic variables, on
percent body fat changes, and on the effects of balanced
versus adlibitum “feed” days, as well as on the benefits of
the different “fasting” regimens is at present lacking.
e primary objective of this systematic review and
meta-analysis was to update the efficacy of IER on weight
loss, limiting the analyses to regimens which actually
included a weekly intermittent energy restriction, i.e.
from 1 up to 6 “fast days” per week. Furthermore, the
impact of IER on fat mass (FM), fat free mass (FFM),
arterial blood pressure (BP) and other cardiometabolic
risk factors was assessed. e effects of IER according to
the specific type of nutritional regimen on all these out-
comes were evaluated too.
Materials andmethods
We followed the Preferred Reporting Items for System-
atic Reviews and Meta-Analyses (PRISMA) guidelines in
the reporting of this study [14].
Search strategy
e following electronic databases were queried using
a combination of search terms until the 31th of May
2018: PubMed (National Library of Medicine), the TRIP
database, the Cochrane Library, EMBASE, and Cumu-
lative Index to Nursing and Allied Health Literature
(CINAHL). e construction of the search strategy was
performed using database specific subject headings and
keywords. Both medical subject headings (MeSH) and
free text search terms were employed. Restrictions to
human studies were placed.
e search terms included combinations of “inter-
mittent fasting” or “alternate day fasting” or “intermit-
tent energy restriction” or “periodic fasting”, and weight
loss, weight gain, obesity, weight, fat mass, blood pres-
sure, blood glucose, insulin, insulin-resistance, insulin
sensitivity, glycated hemoglobin A1c (HbA1c), type 2
diabetes mellitus (T2DM), cholesterol, and triglycerides
(free-term and MESH as possible) (Additional file 1).
ese search strategies were implemented by hand
searching the references of all the included studies and
systematic reviews on the field.
Study selection
We included studies with the following characteristics:
(1) randomized controlled trials (RCTs); (2) a detailed
description of the IER regimen; (3) 75% of energy
restriction on “fast” days, with a maximum cut-off of
500/660 kcal/day for females/males, respectively; (4)
weekly intermittency of energy restriction (from 1 up to 6
“fast” days per week); (5) trial duration > 4weeks; (6) con-
taining as comparator a group on a CER regimen and (7)
including changes in body weight or percent body weight
as one of the study’s outcome.
We excluded studies with the following characteris-
tics: (i) uncontrolled trials or study design other than
RCTs; (ii) studies not including body weight as an out-
come and/or lacking sufficient information on weight
change; (iii) including time restricted feeding interven-
tion; (iv) reporting very-low-calorie or fasting regimens
for > 6 days consecutive/week; and (v) providing > 500–
660kcal/day or not reporting the amount of calorie pre-
scribed on “fast” days.
In trials with multiple interventional arms (i.e. exercise
arm, intervention arm with specific diets), the IER and
the CER arms were considered, while other arms were
not analyzed, since out of the scope of this review.
Two authors (IC, SB) separately screened abstracts
for their inclusion or exclusion; retrieving full text arti-
cles from potentially relevant abstracts. Any discrepancy
about inclusion was resolved by discussing with a third
author (AE).
Outcomes
e primary outcome of the review was evaluating
changes in body weight or in percent body weight. Sec-
ondary outcomes were: changes in body mass index
(BMI), waist circumference, FM, FFM, arterial BP, and
the blood values of fasting glucose and insulin, insu-
lin resistance, insulin sensitivity, HbA1c, total choles-
terol, HDL- and LDL-cholesterol, and triglycerides. e
changes of these outcomes according to the specific type
of IER regimen were also evaluated.
Data collection andextraction
From each included study, the following informa-
tion were extracted (1) first author name and year of
publication; (2) study design; (3) inclusion criteria of
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Cioetal. J Transl Med (2018) 16:371
participants; (4) trial duration; (5) number of subjects
enrolled in each arm; (6) type of dietary intervention;
(7) age, gender, BMI of participants; (8) body composi-
tion (FM and FFM); (9) systolic (SBP) and diastolic blood
pressure (DBP); (10) blood concentrations of fasting glu-
cose, HbA1c, insulin, total cholesterol, HDL-cholesterol,
LDL-cholesterol, and triglycerides; (11) Homeostasis
Model Assessment-Insulin Resistance (HOMA-IR) and
insulin-sensitivity index (Si).
Risk ofbias assessment
All studies were independently assessed by two authors
(IC, SB) using the “Risk of bias” tool developed by the
Cochrane Collaboration for RCTs [15]. e items used
for the assessment of each study were the following: ade-
quacy of sequence generation, allocation concealment,
blinding, addressing of dropouts (incomplete outcome
data), selective outcome reporting, and other potential
sources of bias. A judgment of “L” indicated low risk of
bias, “H” indicated high risk of bias, and “unclear” indi-
cated an unclear/unknown risk of bias. e possible
disagreements were resolved by consensus, or with con-
sultation with a third author (AE).
Data synthesis
Data synthesis was performed only for the outcomes
which were reported by > 3 trials.
e pooled effect sizes were expressed as weighted
mean differences (WMD) and 95% confidence interval
(CI) between IER and CER arms of the mean outcome
values measured at the end of follow-up.
e mean difference of changes from baseline was esti-
mated for each study on the basis of reported baseline
and follow-up measurements. If the standard deviation
for change from baseline was not reported, we imputed
missing values assuming a within-patient correlation
from baseline to follow-up measurements of 0.8 as sug-
gested in the Cochrane handbook [16]. When between-
arms mean differences on change from baseline were
already estimated [17], those data were included. For the
relative weight change from baseline, the non-reported
standard deviations were imputed using the mean stand-
ard deviation of the available studies.
Random-effects models were applied to provide a sum-
mary estimate.
Inter-study heterogeneity was assessed using Cochrane
Q statistic and quantified by I2 test [18].
Subgroup analyses for all outcomes were performed
based on the different dietary regimen of the “feed” days
(balanced vs. ad libitum food intake) and the effects
of the different regimens of “fasting” (5:2 vs. the other
regimens). Weighting of studies was done using generic
inverse variance method.
In order to evaluate the influence of each study on the
overall effect size, sensitivity analysis was conducted
using the one-study remove (leave-one-out) approach.
Potential publication bias was explored using visual
inspection funnel plot asymmetry and Egger’s weighted
regression tests.
Meta-analyses were performed by using the Stata
Metan package (Stata Statistical Software, Release 13;
StataCorp LP, College Station, TX); meta-regressions
and Egger’s weighted regression tests for publication bias
were performed using the metafor package (version 1.9-
7) for R (version 3.1.2, R Foundation for Statistical Com-
puting, Vienna, Austria).
Results
Included studies
e initial literature search identified 8577 records. After
removing duplicates, 6943 records were screened, and,
after excluding articles not meeting the inclusion crite-
ria, 94 records were assessed for eligibility. After further
analysis and quality assessment, a total of 11 studies were
selected for the systematic review and meta-analysis
(Fig. 1). All studies identified were RCTs, reporting an
IER arm and a CER arm comparison; the corresponding
details are shown in Table1. Data relative to participants
involved in exercise-only arms [19] or in high-protein
dietary intervention [20] were not considered, because
not pertinent to the aims of the study.
Characteristics ofthestudies
e total number of subjects included in the present
analysis was 630 at enrolment. During the course of the
trials, 102 patients dropped out. Drop-out rates ranged
from about 2% [21] to 38% for IER arms [22] and from
0% [23] to 50% [22] for CER. e number of participants
analyzed at the end of the RCTs was 528.
ere was a greater number of women among partici-
pants, with the exception of 3 studies with a balanced
number between men and women [21, 22, 24] and 1
enrolling only men [23]. Participants were individuals
with overweight/obesity; in 2 RCTs patients with T2DM
were selected [23, 25], and in 1 RCT patients with mul-
tiple dysmetabolic conditions were enrolled [21]. In all
RCTs except for 2 [23, 25], participants with a stable
weight before the beginning of the study, without his-
tory of bariatric surgery, and without drugs impacting on
weight or the other study outcomes, were studied.
Trials were performed in UK [20, 22, 26], in USA [17,
19, 25, 27], in Australia [23, 24], and Norway [21, 28].
e duration of the studies ranged from 8weeks [27] to
24weeks [17, 21, 23, 26].
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Cioetal. J Transl Med (2018) 16:371
Dietary intervention
Four studies prescribed alternating “fast” and “feed”
days [17, 19, 27, 28]. Six studies used 2 “fast” days and 5
“feed” days per week (5:2 diet) [2124, 26]. In 1 RCT, 5
consecutives “fast” days were prescribed before a 1 “fast”
day/week regimen per 15weeks in the IER arm, while the
other arm (5 “fast” days every 5weeks) was not consid-
ered, since no intermittence within the same week was
present [25]. On “fast” days, diets provided a maximum
of 660kcal/day. In 2 studies, participants were instructed
to consume their meals between 12:00p.m. and 2:00p.m.
on “fast” days to ensure that subjects underwent the same
duration of fasting [17, 19]. In 4 studies, meals of “fast”
days were partially [17, 25] or totally supplied [19, 27].
In 1 study, a commercially available very-low energy for-
mula-based food was assigned in the “fast” days [22].
On “feed” days, 6 studies prescribed healthy and bal-
anced eating pattern, according to the energy require-
ments [17, 20, 22, 25, 26, 28], 4 allowed for adlibitum
food intake based on the participants’ usual eating
[19, 2124] and 1 provided a diet based on the energy
requirements but allowing the access to 5–7 optional
food modules (200 kcal each) [27]. In the comparator
arms, energy was restricted by approximately 25% of the
daily energy requirements in all studies (CER arms).
Dietary compliance andenergy intake assessment
Six studies specifically assessed the compliance to the
diet and the overall energy intake in both arms by filling
7-day food records at different time points [17, 2022, 26,
28]. In 1 study, dieticians evaluated adherence by using
patients’ self-recorded dietary diaries and diet histories
taken during their dietetic appointments [23]. Either
similar adherence between IER and CER [20, 21, 23, 26,
28], a lower [17] or a higher [22] adherence in the IER
arms were reported. Adherence to the recommenda-
tions in the IER arms ranged from 64% [26] to 93% [22]
at the end of the RCTs, but data were difficult to compare
because of their incompleteness and the different meth-
ods employed to evaluate the compliance.
Published studies idenfied through
database search and addional
records idenfied through other
sources (list of references)
(n=8577)
Records screened
(n=6943)
Full-textarcles assessed
for eligibility
(n=94)
Record not meeng the inclusion
criteria
(n=6849)
Studies included in
quantavesynthesis
(meta-analysis)
(n = 11)
Non original arcles or duplicates
(n=1634)
Full-text arcles excluded, with reasons
(n =83)
IER criteria not met (n = 40)
Absence of CER arm (n=16)
Intervenon < 4 weeks (n=3)
Short treatment duraon (n=3)
No RCT (n=7)
Review (n=14)
Idenficaon
Included
Screening
Eligibility
Fig. 1 Flow of the study
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Cioetal. J Transl Med (2018) 16:371
Table 1 Characteristics oftheincluded studies
Author
(year)
[ref]
Study
design Participants Trial
duration N Study groups Age
(years) Males
(n) BMI (kg/
m2)
Waist-c
(cm)
FM
FFM
(kg)
SBP
DBP
(mmHg)
Fasting
glucose
(mg/dL)
Hb1Ac
(%)
Fasting insulin
(µU/mL)
HOMA-IR
(mmol/L*µU/
mL)
Total
chol
(mg/dL)
HDL-c
(mg/
dL)
LDL-c
(mg/dL) TG (mg/dL)
Antoni
(2018)
[22]
RCT 2
parallel
arms
BMI > 25 kg/m2
Age 18–65 years
No comorbidity
8–10 weeks 15aIER (2 days/
week) = 25% of
the energy need
on 2 consecutive
fast days and
energy according
to needs on feed
days
42 ± 4 7 30 ± 1 31 ± 2 123 ± 3 79 ± 2 11 ± 1 162 ± 12 42 ± 4 100 ± 12 97 ± 9
102 ± 3 58 ± 3 74 ± 3 ND 1.6 ± 0.2
12aCER: 600 kcal less
than estimated
needs
48 ± 3 6 31 ± 1 34 ± 3 115 ± 3 79 ± 4 9 ± 1 162 ± 12 39 ± 4 104 ± 8 80 ± 9
102 ± 2 56 ± 3 75 ± 3 ND 1.3 ± 0.1
Carter
(2016)
[24]
RCT 2
parallel
arms
T2DM
BMI 27 kg/m2
Age 18 years
No comorbidity
12 weeks 31 IER (2 days/
week) = 400–
600 kcal/day on
fast days and no
restriction on feed
days
61 ± 8 16 35 ± 5 38 ± 9 134 ± 17 ND ND ND ND ND ND
ND 55 ± 11 84 ± 10 7 ± 1
32 CER = 1200–
1500 kcal/day
every day
62 ± 9 14 36 ± 5 40 ± 11 138 ± 15 ND ND ND ND ND ND
ND 54 ± 9 90 ± 11 8 ± 1
Catenacci
(2016)
[27]
RCT 2
parallel
arms
BMI 30 kg/m2
Age 18–55 years
Non-smokers
No diabetes, CV
diseases, major
comorbidity
8 weeks 15 IER (3 days/
week) = 0 kcal/
day on fast days
alternate and
energy according
to needs, but with
the chance to ask
for more food, on
feed days
40 ± 10 3 36 ± 4 38 ± 8 ND 88 ± 7 13 ± 6 170 ± 33 38 ± 8 100 ± 31 143 ± 56
ND 53 ± 9 ND ND
14 CER = 400 kcal less
than needs
43 ± 8 3 40 ± 6 49 ± 10 ND 92 ± 8 19 ± 6 171 ± 36 39 ± 7 104 ± 29 140 ± 43
ND 61 ± 12 ND ND
Conley
(2018)
[23]
RCT 2
parallel
arms
Men with
BMI 30 kg/m2
Age 55–75 years
No diabetes
No high alcohol
intake or major
comorbidity
24 weeks 12 IER (2 days/
week) = 600 kcal/
day on 2 non-
consecutive fast
days and energy
ad libitum on feed
days
68 ± 3 12 33 ± 2 ND 142 ± 14 108 ± 27 ND 151 ± 35 45 ± 12 77 ± 31 168 ± 53
114 ± 5 84 ± 10 ND
12 CER = 500 kcal less
than needs
67 ± 4 12 36 ± 4 ND 150 ± 18 110 ± 31 ND 166 ± 39 46 ± 12 98 ± 35 212 ± 150
123 ± 10 88 ± 14 ND
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Table 1 (continued)
Author
(year)
[ref]
Study
design Participants Trial
duration N Study groups Age
(years) Males
(n) BMI (kg/
m2)
Waist-c
(cm)
FM
FFM
(kg)
SBP
DBP
(mmHg)
Fasting
glucose
(mg/dL)
Hb1Ac
(%)
Fasting insulin
(µU/mL)
HOMA-IR
(mmol/L*µU/
mL)
Total
chol
(mg/dL)
HDL-c
(mg/
dL)
LDL-c
(mg/dL) TG (mg/dL)
Coutinho
(2017)
[28]
RCT 2
parallel
arms
BMI = 30–40 kg/m2
Age 18–65 years
Inactive, no meno-
pause or major
comorbidity
12 weeks 18 IER (3 days/
week) = 550–
660 kcal/day on
fast days and
energy according
to needs on feed
days
39 ± 11 4 36 ± 3 47 ± 8 ND ND ND ND ND ND ND
ND 60 ± 12
17 CER = 33% of
energy restriction
every day
39 ± 9 2 35 ± 4 43 ± 8 ND ND ND ND ND ND ND
ND 55 ± 9
Harvie
(2011)
[26]
RCT 2
parallel
arms
BMI = 24–40 kg/m2
Premenopausal
women
Age 30–45 years
Non-smokers, not
using OC, no
major comor-
bidity
24 weeks 53 IER (2 days/
week) = 25% of
the energy need
on 2 consecutive
fast days and
energy according
to needs on feed
days
40 ± 4 0 31 ± 5 34
(31–36)
115 (111–
119)
87 (85–88) 7 (6–8) 197 (189–
197)
58
(54–58)
119 (112–
127)
106
(88–124)
102
(98–105)
48
(46–49)
77 (74–79) ND 1.5 (1.3–1.8)
54 CER = 25% energy
restriction every
day
40 ± 4 0 31 ± 5 35
(32–39)
117 (113–
120)
87 (83–88) 7 (6–9) 200 (193–
208)
62
(54–66)
119 (108–
127)
115
(97–124)
102
(99–106)
49
(48–50)
75 (72–78) ND 1.6 (1.3–1.8)
Harvie
(2013)
[20]
RCT 3
parallel
arms
Women with
BMI = 24–45 kg/
m2 or body
fat > 30% of BW
Age 30–45 years
No major comor-
bidity
12 weeks 37 IER (2 days/
week) = 25% of
the energy need
on 2 consecutive
fast days and
energy according
to needs on feed
days
46 ± 8 0 30 ± 4 31
(28–34)
115 (111–
125)
88 (85–90) 6 (5–8) 204 (191–
229)
50
(49–59)
128 (116–
139)
088
(75–102)
101
(97–104)
48.5
(46–50)
ND 5 1.6 (1.3–1.9)
38 IER as above plus
unlimited proteins
and fats (non-SFA)
on fast days
49 ± 7 0 31 ± 6 34
(30–37)
130 (115–
138)
90 (86–92) 7 (6–9) 221 (206–
237)
55
(51–59)
144 (130–
159)
95 (81–109)
104
(99–109)
49
(47–51)
ND 6 1.9 (1.5–2.2)
40 CER = daily 25%
restriction every
day
48 ± 8 0 32 ± 6 36
(32–39)
124 (116–
131)
90 (86–92) 7 (6–9) 205 (193–
218)
51
(48–55)
129 (118–
139)
97 (83–111)
106 (102–
110)
50
(48–52)
ND 6 1.8 (1.5–2.2)
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Cioetal. J Transl Med (2018) 16:371
Author
(year)
[ref]
Study
design Participants Trial
duration N Study groups Age
(years) Males
(n) BMI (kg/
m2)
Waist-c
(cm)
FM
FFM
(kg)
SBP
DBP
(mmHg)
Fasting
glucose
(mg/dL)
Hb1Ac
(%)
Fasting insulin
(µU/mL)
HOMA-IR
(mmol/L*µU/
mL)
Total
chol
(mg/dL)
HDL-c
(mg/
dL)
LDL-c
(mg/dL) TG (mg/dL)
Sundfor
(2018)
[21]
RCT 2
parallel
arms
BMI = 30–45 kg/m2
Age 21–70 years
Waist 84/90 cm
(male/female)
plus another
component of
the metabolic
syndrome
No comorbidity or
alcohol/drug
abuse
24 weeks 54 IER (2 days/
week) = 400–
600 kcal/day on 2
non-consecutive
fast days and
energy as usual
on feed days
50 ± 10 28 35 ± 4 ND 129 ± 13 104 ± 22 ND 192 ± 35 47 ± 13 126 ± 32 162 ± 73
116 ± 10 88 ± 8 6 ± 1
58 CER = 400–600 kcal
less than needs
48 ± 12 28 35 ± 4 ND 128 ± 13 103 ± 13 ND 197 ± 34 45 ± 10 133 ± 32 137 ± 60
116 ± 10 86 ± 9 6 ± 1
Trepanowski
(2017)
[17]
RCT 3
parallel
arms
BMI = 25.0–39.9 kg/
m2
Age 18–65 years
Non-smokers,
inactive
No menopause,
diabetes, CV
diseases
24 weeks 34 IER (alternate d/
week) = 25% of
the energy need
on fast days and
125% of energy
needs on feed
days
44 ± 10 4 34 ± 4 38 ± 7 124 ± 12 90 ± 12 16 ± 14 188 ± 35 57 ± 14 111 ± 13 101 ± 59
ND 55 ± 9 83 ± 9 ND ND
35 CER = daily 25%
restriction every
day
43 ± 12 6 35 ± 4 40 ± 7 122 ± 17 92 ± 18 20 ± 18 184 ± 35 53 ± 11 112 ± 31 97 ± 27
ND 58 ± 12 80 ± 11 ND ND
31 C = no dietary
intervention
44 ± 11 4 34 ± 4 36 ± 10 121 ± 16 87 ± 8 16 ± 9 190 ± 30 59 ± 13 112 ± 31 98 ± 43
ND 53 ± 10 81 ± 11 ND ND
Varady
(2011)
[19]
RCT 4
paral-
lel
arms
BMI = 25–39.9 kg/
m2
Age 35–65 years
Non-smokers,
inactive
No diabetes, CV
diseases
12 weeks 15 IER (3 days/
week) = 25% of
the energy need
on fast days and
ad libitum on
feed days
47 ± 2 3 32 ± 2
ND
ND ND ND ND ND 51 ± 3 141 ± 9 ND
15 CER = 25% energy
restriction every
day
47 ± 3 2 32 ± 2
ND
ND ND ND ND ND 60 ± 6 137 ± 9 ND
15 Moderate exercise
program, no diet
intervention
46 ± 3 2 33 ± 1
ND
ND ND ND ND ND 51 ± 4 122 ± 9 ND
15 C = no dietary/
exercise inter-
vention
46 ± 3 2 32 ± 2
ND
ND ND ND ND ND 57 ± 3 136 ± 10 ND
Table 1 (continued)
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Cioetal. J Transl Med (2018) 16:371
Table 1 (continued)
Author
(year)
[ref]
Study
design Participants Trial
duration N Study groups Age
(years) Males
(n) BMI (kg/
m2)
Waist-c
(cm)
FM
FFM
(kg)
SBP
DBP
(mmHg)
Fasting
glucose
(mg/dL)
Hb1Ac
(%)
Fasting insulin
(µU/mL)
HOMA-IR
(mmol/L*µU/
mL)
Total
chol
(mg/dL)
HDL-c
(mg/
dL)
LDL-c
(mg/dL) TG (mg/dL)
Williams
(1998)
[25]
RCT, 3
paral-
lel
Arms
T2DM
Age 30–70 years
BW > 20% ideal
Not currently on
insulin, no liver,
renal, heart
diseases
20 weeks 18 IER (1 day/
week) = 400–
600 kcal/day
on fast day and
1500–1800 kcal/
day on feed days
51 ± 8 9 35 ± 5 ND ND 177 ± 56 20 ± 11 215 ± 37 41 ± 8 132 ± 35 197 ± 83
ND 8 ± 2 ND
18 IER (5 days/
week) = 400–
600 kcal/day on
fast day every
5 weeks and
1500–1800 kcal/
day on feed days
50 ± 9 7 37 ± 5 ND ND 182 ± 58 17 ± 7 208 ± 39 42 ± 7 131 ± 29 203 ± 239
ND 8 ± 2 ND
18 CER = 1500–
1800 kcal/day
every day
54 ± 7 735 ± 5 ND ND 184 ± 61 22 ± 9 218 ± 42 46 ± 11 127 ± 48 167 ± 89
ND 8 ± 2 ND
BMI body mass index, BW body weight, Chol cholesterol, CV cardiovascular, CER continuous energy restriction, DBP diastolic blood pressure, FFM fat free mass, FM fat mass, IER intermittent energy restriction, HDL-c high
density lipoprotein-cholesterol, LDL-c low density lipoprotein-cholesterol, ND no data, OC oral contraceptives, RCT randomized controlled trial, SFA saturated fatty acids, SBP systolic blood pressure, TG triglycerides, T2DM
type 2 diabetes mellitus, Waist-c waist circumference, Wk week
a Not available the baseline data of all the randomized patients; the study reported the baseline characteristics of the study completers only
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Cioetal. J Transl Med (2018) 16:371
Risk ofbias assessment
Some of the analyzed trials were characterized by the
lack of information about the randomization procedures
(Additional file2). If blinding of participants was not fea-
sible owing to the nature of the interventions, data about
blinding of the personnel performing the laboratory or
statistical analyses were always unknown, except for 1
study [20]. Dropouts were higher in the IER arms [17, 26,
28] or in the CER arms [20, 22, 24, 25], thus introducing
a possible selection bias between-arms, but intention-to
treat analyses were performed by all studies, except for 1
RCT [22], where data of the completers only have been
reported. Finally, most trials appeared to be free of selec-
tive outcome reporting and of other sources of bias, apart
from 1, where body weight at baseline was not reported
[19].
Meta-analysis
All the outcomes of interest of this systematic review
are reported in Additional file3. Data synthesis was per-
formed for the outcomes reported by >3 trials, therefore
data relative to Si values were not pooled.
Weight loss
All RCTs reported weight loss in the IER arms during the
intervention, ranging from 5.2% [19] of initial weight to
12.9% [28], while in the CER arms, changes ranged from
4.3% [20] to 12.1% [28] (Additional file3). Pooled data
from random-effect analysis did not show a significant
effect of IER on weight loss (WMD: 0.61kg, 95% CI
1.70 to 0.47; p = 0.27) (Fig. 2). e estimated effect on
body weight did not change in the leave-one-out sensitiv-
ity analysis (data not shown).
Subgroup analyses based on the type of regimen (5:2
vs. other regimens) as well as on the dietary character-
istics of the “feed” days of the IER interventions (ad libi-
tum vs. balanced food intake) showed consistent results,
as reported in Additional file4. Analyses were repeated
after the exclusion of the trial prescribing 5 consecutives
“fast” days and then 1 “fast” day/week per 15weeks [25],
and the results did not change (WMD: 0.36kg, 95% CI
1.48 to 0.77; p = 0.54). Finally, the RCT reporting the
percent relative variations of the endpoints only [19] was
included in the analyses, and the estimated effect size of
weight change did not show any between-arms difference
(WMD: 0.08, 95% CI 0.23 to 0.07; p = 0.29).
Similarly, the percent weight loss was similar in both
arms (WMD: 0.38%, 95% CI 1.16 to 0.40; p = 0.34)
and the results did not differ either in the subgroup anal-
yses (Additional file5) or in the leave-one-out sensitivity
analysis.
Other anthropometric measures
Seven out of the 11 included RCTs reported changes in
FM and FFM [17, 20, 22, 24, 2628]. FM was measured
by different methods: body impedance analysis (BIA)
[20, 22]; dual X-ray absorptiometry (DXA) [17, 24, 27];
impedance [26]; air displacement plethysmography [28].
Pooled results showed no difference between-arms in
FM (WMD: 0.23kg, 95% CI 1.23 to 0.77; p = 0.66) a s
well as in FFM (WMD: 0.22kg, 95% CI 1.01 to 0.56;
p = 0.58), as shown in Additional file 6. ose results
were consistent both at subgroup analyses and at sensi-
tivity analyses. Five RCTs assessed waist circumference
[2023, 26] without showing any differences between
arms (WMD: 0.17cm; 95% CI 1.74 to 1.39; p = 0.83).
Cardiometabolic biomarkers
Pooled data obtained from glucose, HbA1c, insulin
and HOMA-IR are presented in Fig. 3a–d respectively.
Changes in fasting glucose and HbA1c values were
reported respectively in 7 [17, 2023, 26, 27] and 4 [21,
2426] trials. Random-effect analysis showed no dif-
ference either on glucose (WMD: 0.49 mg/dL, 95%
CI 1.98 to 0.99; p = 0.51) or HbA1c (WMD: 0.02%,
95% CI 0.10 to 0.06; p = 0.62) changes in the IER when
compared to CER arms with consistent results in sub-
group/sensitivity analyses.
On the contrary, fasting insulin values were signifi-
cantly reduced with IER (WMD = 0.89 µU/mL; 95%
CI 1.56 to 0.22; p = 0.009; I2 = 0%) and the estimated
effect appeared robust in the leave-one-out sensitivity
analysis (data not shown). Moreover, subgroup analy-
ses showed that the 5:2 regimens were associated with
increased insulin reductions (WMD: 0.99 µU/mL; 95%
CI 1.67 to 0.30; p = 0.005; I2 = 0) (Additional file7).
All the RCTs evaluating fasting insulin values included
a balanced energy regimen for the “feed” days. HOMA-
IR values were reduced, though not significantly, in the
IER regimens (WMD = 0.15mmol/L × µU/mL; 95% CI
0.33 to 0.02; p = 0.09).
Only 1 RCT evaluated insulin sensitivity (Si) by a fre-
quently sampled intravenous glucose tolerance [21],
without between-arms differences.
Pooled data obtained from 8 RCTs [17, 2023, 2527]
did not show any significant effect of IER on triglyc-
eride concentrations (WMD: 3.11 mg/dL, 95% CI
9.76 to 3.54; p = 0.36) (Fig. 4a). However, subgroup
analyses showed a slightly significant triglyceride reduc-
tion in the IER arms employing other fasting regi-
mens (WMD = 14.4mg/dL 95% CI 28.6 to 0.23;
p = 0.046; I2 = 0%). Characteristics of the “feed” days were
not associated with differences in triglyceride changes
(Additional file8). HDL-cholesterol levels increased after
IER regimens, albeit not significantly (WMD = 1.72 mg/
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Cioetal. J Transl Med (2018) 16:371
dL 95% CI 0.20 to 3.63; p = 0.07) (Fig. 4c). Subgroup
analysis revealed a significant HDL-cholesterol increase
with a balanced diet on “feed” days (WMD = 2.88 mg/
dL 95% CI 0.66 to 5.09; p = 0.011; I2 = 0%) compared with
ad libitum eating (Additional file 9). No between-arm
differences were found for total cholesterol and LDL-
cholesterol (Fig.4b, d). Finally, changes in both SBP and
DBP did not significantly differ between arms (Additional
file10).
Publication bias
We used the Egger’s test for funnel plot asymmetry to
detect a potential publication bias on reporting results on
weight change. Test result (p = 0.15) did not suggest any
asymmetry in the funnel plot (Additional file11).
Safety
No major adverse events were reported. Only 1 patient
from the IER arm of the RCT supplying 0 kcal during
“fast” days developed gallbladder dyskinesia and under-
went cholecystectomy after completing the study, but
this event was reported to be unrelated to the interven-
tion [27]. Minor physical or psychological adverse effects,
such as lack of energy, headaches, feeling cold, constipa-
tion, bad breath, lack of concentration, bad temper, were
reported in a minority of participants from the IER arms
(< 20%) in a few studies [20, 21, 23, 26]. On the other
hand, hunger was reported in the first weeks by about
half of participants to a 5:2 regimen in 1 trial, but this
symptom improved over time [23].
Discussion
An intermittent regimen of energy restriction (at least
1day/week) determined a loss in body weight and per-
cent body weight similar to continuous (non-intermit-
tent) energy restriction. Interestingly, a slight reduction
in fasting insulin concentrations was evident with IER
regimens employing 2days/week “fast”, but the clinical
relevance of this result is uncertain.
Eects ofIER onweight loss andfat mass
Most systematic reviews and meta-analyses demon-
strated that IER regimens achieved comparable weight
loss as CER regimens [4, 5, 9], reporting an overall weight
loss ranging from 4 to 8% [2, 3, 7, 9], and a difference of
4.14kg to +0.08kg versus the comparator arms [4, 5,
29]. Our results are in accordance, even if the trials previ-
ously included differed from ours, since we have included
only RCTs with a at least 1day/week and no more than
6day/week of “fasting”, and with an extremely low energy
supply during the “fast” days. is latter choice derived
from the idea of studying conditions simulating as much
as possible a condition of fasting, whose benefits, proven
by animal studies, seem to depend on the shift in metab-
olism from glucose utilization and fat synthesis/storage
towards reduced insulin secretion and fat mobilization/
oxidation [30, 31].
ere is no clear definition of IER, and intermittent
regimens providing up to 800kcal [5, 9], with 7 “fast”
days [4, 6, 9, 29], including time-restricted feeding [2,
68, 32], with unlimited energy restriction as a compara-
tor group [2, 3, 57], or not randomized controlled trials
[2] have been included within previous reviews. We have
taken care to define precise inclusion criteria to limit var-
iability and increase the comparability among trials, and
we have obtained a low heterogeneity.
It could be hypothesized that the very low caloric
intake on “fast” days determined an overall lower
caloric intake in the IER arms, which were therefore
difficult to be compared with the CER arms. In the
only RCT where water and calorie-free beverages were
allowed in the “fast” days, a significant between-arms
difference in energy intake was evident [27]; in two
studies a between-arms difference of 300–400kcal was
observed [22, 23] while most RCTs reported a negligi-
ble between-arms difference (~ 100kcal) [17, 20, 21, 25,
26]. Consistently, our sensitivity and subgroup analyses
did not find significant between-arms differences.
Furthermore, the percent weight loss was highly
overlapping, and no apparent superiority of a dietary
regimen was evident. Indeed, participants of the IER
arms from all RCTs lost 5% of their initial weights,
thus confirming the clinical usefulness of this approach
at least in the short term, i.e. within 24weeks.
Previous reviews reported a FM loss ranging from 4
to 7% [3] to 11–16% [2] in the IER arms, and the only
meta-analysis evaluating this outcome reported a dif-
ferential loss of 1.38 kg with respect to comparator
arms [5]. We failed to find significant between-arms
difference for this outcome, suggesting that such a regi-
men could be a valid, but not superior alternative to
CER.
Intriguingly, participants to the IER regimens usually
did not consume as much food in the “feed” days as to
compensate for the caloric restriction of the “fast” days,
thus suggesting that IER could reduce food intake even
in the “feed” days, without compensatory overeating [6,
31]. is finding was not confirmed by all studies [28,
33, 34]. Furthermore, adverse events were sometimes
higher with the IER regimens [20, 21, 26], and the partici-
pants reported stronger feelings of hunger [21, 23]. e
compliance and adherence to the intervention diets was
heterogeneous among trials, the attrition rate was often
higher in the IER arms [17, 22, 24, 26, 31, 35], and the
percentage of participants planning to continue with the
dietary regimen beyond 6months was lower in the IER
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Cioetal. J Transl Med (2018) 16:371
arms [26]. Overall, these data do not support the fact that
IER is easier and more acceptable than CER to everyone.
Moreover, the reduction in resting energy expenditure,
i.e. the compensatory metabolic response which reduces
the degree of weight loss, has been reported to be either
reduced (favoring weight loss) [27, 36] or increased
(attenuating weight loss) [22, 28] with IER regimens.
Indeed, some studies suggest that IER evokes the same
adaptive response as CER [6, 37].
e hypothesized benefits of IER, extensively studied
in animal models, included the use of fats during severe
energy restriction with preferential reduction of adipose
mass, the stimulation of browning in white adipose tis-
sue, increased insulin sensitivity, lowering of leptin and
increased human growth hormone, ghrelin and adi-
ponectin circulating levels, reduced inflammation and
oxidative stress [30]. e trigger of adaptive cell response
leading to enhanced ability to cope with stress, improved
autophagy by sirtuin-1 activity stimulation, modification
of apoptosis, increase of vascular endothelial growth fac-
tor expression in white adipose tissue, the action on the
metabolism via Forkhead Box A genes, and reduction
of advance glycation end-products might be all possible
metabolic pathways explaining the beneficial effects of
IER [7, 30, 38, 39]. In mice, IER determined metabolic
improvements and weight loss as a consequence of a shift
in the gut microbiota composition, leading to an increase
in the production of acetate and lactate and to the selec-
tive upregulation of monocarboxylate transporter in
beige adipose cells which stimulate beige fat thermogen-
esis [40]. At present, many of these adaptive mechanisms
have been demonstrated in animal experimental models
but not in humans, thus more research is still needed.
Eects ofIER oncardiometabolic markers
IER regimens were associated with lower circulating
insulin values; a significant reduction was evident for
the 5:2 “fasting” regimen only. Indeed, two RCTs, both
employing this regimen, determined the difference [20,
26]. Our data are in line with the results of a previous
meta-analysis reporting a significantly higher reduction
in fasting insulin ( 0.67 µU/mL) in the IER arms [5].
e difference we found (0.89 µU/mL) was statistically
significant, but not clinically relevant, above all consider-
ing the fact that participants to the included RCTs were
overweight/obese and therefore probably insulin-resist-
ant individuals.
Our data synthesis on glucose, HOMA-IR, HbA1c
showed no between-arms difference. We did not include
patients with T2DM from 2 RCTS in the pooled analy-
sis on fasting glucose, since most participants were on
hypoglycemic drugs and their glycemic values would be
Fig. 2 Meta-analysis of the effects of intermittent energy restriction versus continuous energy restriction on weight loss. MD (mean difference)
indicates the mean difference on change from baseline of the IER vs. the CER arms. The plotted points are the mean differences and the horizontal
error bars represent the 95% confidence intervals. The grey areas are proportional to the weight of each study in the random-effects meta-analysis.
The vertical dashed line represents the pooled point estimate of the mean difference. The solid black line indicates the null hypothesis (MD = 0)
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Cioetal. J Transl Med (2018) 16:371
certainly influenced by the treatment [24, 25]. Highly
contrasting human studies are available about the ben-
efits of IER on glucose metabolism and insulin sensitivity
[3, 6, 31], contrarily to animal studies strongly suggesting
a benefit in T2DM prevention [1, 31]. e improvements
in glucose homeostasis might be therefore comparable to
those obtained by continuous energy restrictions.
Our meta-analysis did not show significant between-
arms difference in lipid values and arterial blood pres-
sure, with the exception of a small difference in subgroup
analyses on triglyceride concentrations (14mg/dL) and
HDL-cholesterol (+2.88mg/dL), not meaningful from a
clinical point of view. Most studies showed reduction in
triglyceride levels between 15 and 42% in the IER arms
[31, 41], and the only available meta-analysis reported
a between-arms not significant difference of 2.65 mg/
dL [5]. Reduction in total cholesterol, LDL-cholesterol
in the IER arms ranged respectively between 6–25%,
7–32%, with small effects on HDL-cholesterol [1, 31],
and between-arms differences resulted not significant
[5]. Intriguingly, a few studies reported that IER regimens
determined an increase in LDL particle size [19, 42], and
reduced post-prandial hypertriglyceridemia [22], thus
potentially conferring cardio-protection, since the lower
the LDL size, the higher the oxidizability and the suscep-
tibility to arterial penetration, and higher post-prandial
hyperlipemia is a marker of atherosclerosis progression.
Furthermore, fasting can act on many enzymes impli-
cated in lipid and lipoprotein metabolism [27]. How-
ever, all these reports need confirmation in larger human
RCTs.
Similarly, data on arterial BP were controversial, with
the majority of human studies reporting no differences
between IER and CER regimens [1, 5, 31, 41]. Indeed,
most of the published studies and RCTs included normo-
tensive subjects at baseline, making it difficult to identify
differences between-arms.
erefore, unlike the very promising data on animals,
evidence is not sufficiently robust to suggest the superi-
ority of intermittent vs. continuous caloric restriction
regimens on the main cardiovascular factors in humans.
Fig. 3 Meta-analysis of the effects of intermittent energy restriction versus continuous energy restriction on fasting glucose (a), HbA1c (b), insulin
(c) and HOMA-IR (d) values. MD (mean difference) indicates the mean difference on change from baseline of the IER vs. the CER arms. The plotted
points are the mean differences and the horizontal error bars represent the 95% confidence intervals. The grey areas are proportional to the weight
of each study in the random-effects meta-analysis. The vertical dashed line represents the pooled point estimate of the mean difference. The solid
black line indicates the null hypothesis (MD = 0)
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Cioetal. J Transl Med (2018) 16:371
Clinical implications
Weight loss maintenance should be an integral compo-
nent of the management of obesity, owing to the weight
regain usually occurring with time. e 2 RCTs includ-
ing longer follow-ups (24months) did not find between-
arms differences in weight loss maintenance [17, 27].
Studies with longer follow-ups, evaluating the long-
term sustainability, adherence to, and safety of IER regi-
mens are needed. Furthermore, no RCT evaluated hard
endpoints, such as cardiovascular outcomes or T2DM
incidence. Two observational cohort studies found that
fasting was associated with a lower prevalence of coro-
nary artery diseases or diabetes diagnosis but are limited
by a lack of a comprehensive dietary history and many
potential bias [43, 44]. It could be hypothesized that IER
regimens should be proposed in clinical practice, since
it is possible that some individuals find easier to reduce
their energy intakes for 1 or more days per week, rather
than every day. It is well known that a single diet fit not
all, and in the choice of the individual’s tailored regimen,
IER strategies should be considered by health care pro-
fessionals. In this way, data on the feasibility of these regi-
mens in “real life” would be obtained.
Strengths andlimitations
is is, to our knowledge, the largest and updated meta-
analysis on the effects of IER on weight loss and multiple
metabolic outcomes, setting strict inclusion criteria to
increase comparability among studies.
e high variability among the RCTs in the feeding
protocols, the limited follow-up, the small sample sizes,
the high drop-out rates potentially leading to selection
bias, the limited reporting of adverse events and blind-
ing of investigators about arm allocation, or other meth-
odological problems are all limitations to be considered.
Finally, most studies were performed by the same authors
and the majority of subjects included were adult healthy
women, thus limiting the generalizability of the results.
Fig. 4 Meta-analysis of the effects of intermittent energy restriction versus continuous energy restriction on triglycerides (a), total cholesterol (b),
HDL-cholesterol (c) and LDL-cholesterol (d) values. MD (mean difference) indicates the mean difference on change from baseline of the IER vs. the
CER arms. The plotted points are the mean differences and the horizontal error bars represent the 95% confidence intervals. The grey areas are
proportional to the weight of each study in the random-effects meta-analysis. The vertical dashed line represents the pooled point estimate of the
mean difference. The solid black line indicates the null hypothesis (MD = 0)
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Cioetal. J Transl Med (2018) 16:371
Conclusion
In overweight/obese adults, IER is as effective as CER
for promoting weight loss and metabolic improvements
in the short term. Further long-term investigations are
needed to draw definitive conclusions.
Additional les
Additional le1. Electronic search strategy.
Additional le2. Risk of bias assessment in the trials included in the
systematic review.
Additional le3. Changes in outcomes at the end of the trials.
Additional le4. Subgroup analysis of weight loss based on the type of
regimen (a) and on dietary characteristics of the “feed” days (b).
Additional le5. Percent weight loss (a) and subgroup analysis of per-
cent weight loss based on the type of regimen (b) and dietary characteris-
tics of the “feed” days (c).
Additional le6. Meta-analysis of the effects of intermittent energy
restriction versus continuous energy restriction on body composition (a)
and waist circumference (b).
Additional le7. Subgroup analysis of fasting insulin based on the type
of regimen.
Additional le8. Subgroup analysis of triglycerides based on the type of
regimen (a) and dietary characteristics of the “feed” days (b).
Additional le9. Subgroup analysis of HDL-cholesterol based on the
type of regimen (a) and dietary characteristics of the “feed” days (b).
Additional le10. Meta-analysis of the effects of intermittent energy
restriction versus continuous energy restriction on systolic blood pressure
(SBP) (a) and diastolic blood pressure (DBP) (b).
Additional le11. Funnel plot for publication bias detection on weight
loss changes.
Abbreviations
BIA: body impedance analysis; BMI: body mass index; BP: blood pressure; CER:
continuous energy restriction; CI: confidence interval; CINAHL: Cumulative
Index to Nursing and Allied Health Literature; DBP: diastolic blood pressure;
DXA: dual X-ray absorptiometry; FFM: fat free mass; FM: fat mass; HbA1c:
glycated hemoglobin A1c; HOMA-IR: Homeostasis Model Assessment-Insulin
Resistance; IER: intermittent energy restriction; MeSH: medical subject head-
ings; RCTs: randomized controlled trials; Si: insulin-sensitivity index; SBP:
systolic blood pressure; T2DM: type 2 diabetes mellitus; WMD: weight mean
difference.
Authors’ contributions
IC participated in the conception and design of the study, data collection and
revision, interpretation of the findings of the study, manuscript writing and
revision. AE participated in the data analysis, interpretation of the findings,
manuscript writing and revision. VP, GC participated in the data analysis,
interpretation of the findings, and manuscript revision. LSo, LSa, FP, FC, EG
participated in the interpretation of the findings, and manuscript revision. SB
participated in the conception and design of the study, data collection and
revision, manuscript writing and revision. All authors read and approved the
final manuscript.
Author details
1 Interuniversity Center for Obesity and Eating Disorders, Department of Medi-
cine and Surgery, Federico II University Hospital, Pansini, 5, Naples 80131, Italy.
2 Unit of Clinical Epidemiology, CPO, “Città della Salute e della Scienza” Hospital
of Turin, Turin, Italy. 3 Department of Medical Sciences, University of Turin, c.so
AM Dogliotti 14, 10126 Turin, Italy. 4 Department of Health Sciences, University
of Milan, Milan, Italy.
Acknowledgements
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Availability of data and materials
All data analyzed during this study are included in this published article.
Consent for publication
Not applicable.
Ethics approval and consent to participate
Not applicable.
Funding
Not applicable.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in pub-
lished maps and institutional affiliations.
Received: 31 October 2018 Accepted: 14 December 2018
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Supplementary resources (11)

... [17][18][19] However, other studies have found that time-specific diets are not superior to energy restriction in improving cardiovascular and metabolic outcomes. [20][21][22][23][24] More recent meta-analyses of randomized controlled trials in overweight or obese patients indicated that intermittent energy restriction involving 2-3 days of periodic fasting led to improved weight loss and reduced body fat versus continuous energy restriction. 25,26 In summary, there is a lack of agreement between clinical studies on whether IF may lead to improved metabolic outcomes. ...
... 17,20,22 In addition, body mass index, glycemic control, age, sex, physical activity, and geographic and ethnic differences between individuals had major implications on the metabolic outcomes of different IF diets. 17,18,20,21,23,25 With these limitations withstanding, it is possible that personalized, individually tailored time-restricted diets will be more feasible, tolerable and sustainable, and will result in more consistent long-term metabolic improvements. There are several theories hypothesizing about the mechanisms potentially underlying the possible benefits of IF diets compared to ad libitum feeding. ...
... In agreement with the effect of IF diets on β cells regeneration in rodents, human randomized clinical trials suggested a superior effect of periodic fasting (5:2 diet) on fasting insulin compared to a matched group with daily caloric restriction. 23,25,125 Blood pressure. Hypertension refers to persistently high arterial blood pressure that, if left untreated, can lead to a number of devastating consequences such as heart failure and peripheral vascular disease. ...
Article
In recent years, intermittent fasting (IF), including periodic fasting and time‐restricted feeding (TRF), has been increasingly suggested to constitute a promising treatment for cardiometabolic diseases (CMD). A deliberate daily pause in food consumption influences the gut microbiome and the host circadian clock, resulting in improved cardiometabolic health. Understanding the molecular mechanisms by which circadian host‐microbiome interactions affect host metabolism and immunity may add a potentially important dimension to effective implementation of IF diets. In this review, we discuss emerging evidence potentially linking compositional and functional alterations of the gut microbiome with IF impacts on mammalian metabolism and risk of development of hypertension, type 2 diabetes (T2D), obesity, and their long‐term micro‐ and macrovascular complications. We highlight the challenges and unknowns in causally linking diurnal bacterial signals with dietary cues and downstream metabolic consequences and means of harnessing these signals toward future microbiome integration into precision medicine. Highlights Time‐specific diet is a novel nutritional approach to prevent and treat cardiometabolic disease. Feeding‐fasting cycles shape gut microbial composition and metabolite production. These alterations may play a causative role in driving the cardiometabolic benefits of intermittent fasting. Despite the impressive results in animals, human studies show contradicting results, possibly due to intraindividual variation involved in the host‐microbiome response to diet. Better mechanistic understanding is required to develop personalized dietary interventions to treat cardiometabolic diseases.
... Numerous recent meta-analyses and reviews confirm this contention [1][2][3][4][5], although the benefits are not universal [6], and perhaps due to insufficient lengths of sustained fasting (> 16 h). Of the myriad types of IF, several are particularly common and have shown modest efficacy on WL and health improvement: a) "periodic" IF includes fasting one (IF1; < 36 h) to two (IF2; > 48 h) days/week and feeding ad libitum (eating freely) the remaining five or six days [7]; b) alternateday fasting (ADF), consisting of no (or very low) energy (calorie) intake every second day while eating ad libitum the other days [8]; and c) time-restricted eating (TRE) consisting of fasting for 12-20 h/day and the remaining time-consuming calories freely [9]. The IF-mediated benefits are associated with increased oxidation of fatty acids (lipolysis) and ketone body formation (ketogenesis), activated cell-signaling pathways (insulin sensitivity, reduced inflammation, autophagy), and preservation of lean body mass, known as "metabolic switching" [1][2][3][4][5][6][7][8][9][10][11]. ...
... Of the myriad types of IF, several are particularly common and have shown modest efficacy on WL and health improvement: a) "periodic" IF includes fasting one (IF1; < 36 h) to two (IF2; > 48 h) days/week and feeding ad libitum (eating freely) the remaining five or six days [7]; b) alternateday fasting (ADF), consisting of no (or very low) energy (calorie) intake every second day while eating ad libitum the other days [8]; and c) time-restricted eating (TRE) consisting of fasting for 12-20 h/day and the remaining time-consuming calories freely [9]. The IF-mediated benefits are associated with increased oxidation of fatty acids (lipolysis) and ketone body formation (ketogenesis), activated cell-signaling pathways (insulin sensitivity, reduced inflammation, autophagy), and preservation of lean body mass, known as "metabolic switching" [1][2][3][4][5][6][7][8][9][10][11]. Interestingly, these mechanisms are typically not fully activated until at least 24 h of fasting [5]. ...
... Our finding of significant weight loss and improved body composition outcomes with IF agrees with recent metaanalyses and reviews [2,[5][6][7][8][9][10][11], although this is not a universal finding [6][7][8][9][10][11][12][13][14][15][16][17][18]. Some data also suggest a substantial Fig. 3 Individual changes in body weight and waist circumference during WL between IF1-P and IF2-P loss of lean body mass may occur with IF depending on the length and degree of fasting [6,18] which is a common observation during weight loss [18]. ...
Article
Full-text available
Background Intermittent fasting (IF), consisting of either a one-day (IF1) or two consecutive days (IF2) per week, is commonly used for optimal body weight loss. Our laboratory has previously shown an IF1 diet combined with 6d/week of protein pacing (P; 4–5 meals/day evenly spaced, ~ 30% protein/day) significantly enhances weight loss, body composition, and cardiometabolic health in obese men and women. Whether an IF1-P or IF2-P, matched for weekly energy intake (EI) and expenditure (EE), is superior for weight loss, body composition, and cardiometabolic health is unknown. Methods This randomized control study directly compared an IF1-P ( n = 10) versus an IF2-P ( n = 10) diet on weight loss and body composition, cardiovascular (blood pressure and lipids), hormone, and hunger responses in 20 overweight men and women during a 4-week weight loss period. Participants received weekly dietary counseling and monitoring of compliance from a registered dietitian. All outcome variables were assessed pre (week 0) and post (week 5). Results Both groups significantly reduced body weight, waist circumference, percent body fat, fat mass, hunger, blood pressure, lipids, glucose, and increased percent fat-free mass ( p < 0.05). However, IF2-P resulted in significantly greater reductions in body weight (-29%) and waist circumference (-38%) compared to IF1-P ( p < 0.05), and showed a strong tendency for greater reductions in fat mass, glucose, and hunger levels ( p < 0.10) despite similar weekly total EI (IF1-P, 9058 ± 692 vs. IF2-P, 8389 ± 438 kcals/week; p = 0.90), EE (~ 300 kcals/day; p = 0.79), and hormone responses ( p > 0.10). Conclusions These findings support short-term IF1-P and IF2-P to optimize weight loss and improve body composition, cardiometabolic health, and hunger management, with IF2-P providing enhanced benefits in overweight women and men. Trial registration This trial was registered March 03, 2020 at www.clinicaltrials.gov as NCT04327141 .
... The main characteristics of the included reviews and RCTs are presented in Table 1; Table 2, respectively. As shown in Table 1, only one of the twelve systematic reviews was a Cochrane review [32], and the remaining were non-Cochrane systematic reviews [19,[24][25][26][33][34][35][36][37][38][39]. Most participants in the included reviews were adults with overweight or obese and were over 18 years of age. ...
... Most participants in the included reviews were adults with overweight or obese and were over 18 years of age. The target populations of ten reviews included adults with T2DM [19,25,26,32,[34][35][36][37][38][39], of which only one review included adults with T2DM [36]. All analyzed articles of the included reviews were RCTs ranging from five to forty in number. ...
... The non-primary IER protocols prescribed in all included reviews differed from the duration of fasting days to the intensity of calorie restriction. Regular diet or no control were also considered as the comparison in the studies of eleven [19,[24][25][26][32][33][34][35][36]38,39] and four [19,25,34,37] included reviews, respectively. One review included studies that considered the Mediterranean diet as a comparison [36], and one included VLED [34]. ...
Article
Full-text available
There is considerable heterogeneity across the evidence regarding the effects of intermittent energy restriction and continuous energy restriction among adults with overweight or obesity which presents difficulties for healthcare decision-makers and individuals. This overview of systematic reviews aimed to evaluate and synthesize the existing evidence regarding the comparison of the two interventions. We conducted a search strategy in eight databases from the databases’ inception to December 2021. The quality of 12 systematic reviews was assessed with A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2) and the Grading of Recommendations Assessment, Development and Evaluation (GRADE). One review was rated as high quality, 1 as moderate, 4 as low, and 6 as critically low. A meta-analysis of the original studies was conducted for comparison of primary intermittent energy restriction protocols with continuous energy restriction. Intermittent energy restriction did not seem to be more effective in weight loss compared with continuous energy restriction. The advantages of intermittent energy restriction in reducing BMI and waist circumference and improvement of body composition were not determined due to insufficient evidence. The evidence quality of systematic reviews and original trials remains to be improved in future studies.
... Whereas both IF and continuous daily CR seem to be effective in reducing body weight and fat mass, how fat-free mass is affected by these two interventions is still a matter of debate [30,38]. According to several meta-analyses, both IF and CR interventions produced similar changes in body weight, fat mass, fat-free mass and waist circumference [7,34,35,[39][40][41], provided that the adherence to interventions is similar [7,40,41]. However, a recently published study, imposing a relatively tightly matched degree of energy restriction, has reported that ADF induced lower fat and greater fat-free mass loss (~−0.74 ...
... Whereas both IF and continuous daily CR seem to be effective in reducing body weight and fat mass, how fat-free mass is affected by these two interventions is still a matter of debate [30,38]. According to several meta-analyses, both IF and CR interventions produced similar changes in body weight, fat mass, fat-free mass and waist circumference [7,34,35,[39][40][41], provided that the adherence to interventions is similar [7,40,41]. However, a recently published study, imposing a relatively tightly matched degree of energy restriction, has reported that ADF induced lower fat and greater fat-free mass loss (~−0.74 ...
... A recent meta-analysis including 91 studies has shown that Ramadan produces a small but significant reduction in serum triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), diastolic blood pressure, and an increase in high-density lipoprotein cholesterol (HDL-C) [49]. Two other meta-analyses have shown that IF regimens reduced total cholesterol and systolic blood pressure compared to unrestricted eating, although the clinical relevance of the magnitude of these reductions may be debatable [34,40]. Meta-analyses considering only ADF and TRE studies were also conducted. ...
Article
Full-text available
This review summarizes the effects of different types of intermittent fasting (IF) on human cardiometabolic health, with a focus on energy metabolism. First, we discuss the coordinated metabolic adaptations (energy expenditure, hormonal changes and macronutrient oxidation) occurring during a 72 h fast. We then discuss studies investigating the effects of IF on cardiometabolic health, energy expenditure and substrate oxidation. Finally, we discuss how IF may be optimized by combining it with exercise. In general, IF regimens improve body composition, ectopic fat, and classic cardiometabolic risk factors, as compared to unrestricted eating, especially in metabolically unhealthy participants. However, it is still unclear whether IF provides additional cardiometabolic benefits as compared to continuous daily caloric restriction (CR). Most studies found no additional benefits, yet some preliminary data suggest that IF regimens may provide cardiometabolic benefits in the absence of weight loss. Finally, although IF and continuous daily CR appear to induce similar changes in energy expenditure, IF regimens may differentially affect substrate oxidation, increasing protein and fat oxidation. Future tightly controlled studies are needed to unravel the underlying mechanisms of IF and its role in cardiometabolic health and energy metabolism.
... In a systematic review and meta-analysis of RCTs intermittent versus continuous energy restriction on weight loss and cardio-metabolic outcomes have been investigated. The included eleven trials with a duration from 8 to 24 weeks resulted in a similar weight loss between the two intervention groups [46]. Compared to a continuous energy restriction, intermittent fasting leads to similar weight loss and similar improvement of cardio-metabolic parameters [47][48][49]. ...
Article
Full-text available
Obesity caused by a positive energy balance is a serious health burden. Studies have shown that obesity is the major risk factor for many diseases like type 2 diabetes mellitus, coronary heart diseases, or various types of cancer. Therefore, the prevention and treatment of increased body weight are key. Different evidence-based treatment approaches considering weight history, body mass index (BMI) category, and co-morbidities are available: lifestyle intervention, formula diet, drugs, and bariatric surgery. For all treatment approaches, behaviour change techniques, reduction in energy intake, and increasing energy expenditure are required. Self-monitoring of diet and physical activity provides an effective behaviour change technique for weight management. Digital tools increase engagement rates for self-monitoring and have the potential to improve weight management. The objective of this narrative review is to summarize current available treatment approaches for obesity, to provide a selective overview of nutrition trends, and to give a scientific viewpoint for various nutrition concepts for weight loss.
Chapter
Noncommunicable chronic diseases have been on the rise for decades. Almost 10% of the world adult population lives with type 2 diabetes mellitus (T2DM)—a leading cause of severe complications associated with disability and premature mortality. Worldwide, nearly 500 million adults are living with T2DM and 4.2 million deaths were caused directly by the disease. Dietary quality is a major component influencing the development of T2DM, due to diet-related inflammatory processes, linked to metabolically unhealthy obesity (MUO) and metabolic syndrome (MetS). In addition to systemic and tissue-specific low-grade chronic inflammation, characterized by mediators such as various cytokines, T2DM is characterized by a disturbed homeostasis of oxidative stress, as well as a dysregulated glucose and lipid metabolism. Poor inflammatory and antioxidant status have been related to an enhanced risk of developing MUO, MetS, and T2DM. However, diet also is an important source of antioxidants, which are antiinflammatory and may reduce disease risk and improve symptomology. This includes dietary patterns rich in fruits/vegetables, which are good sources of fiber, vitamins, minerals, and phytochemicals such as polyphenols, and low in animal products, ultraprocessed foods, sugar, saturated fats, total calories, and salt. Mechanistic studies have highlighted that antiinflammatory and antioxidant diets might positively influence several cellular processes. These include direct effects on the homeostasis of reactive oxygen species (ROS) such as quenching effects by antioxidants, but also the interaction of dietary constituents with transcription factors, especially with nuclear factor kappa-B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf-2), important for regulating inflammation and oxidative stress, respectively. In this chapter, we evaluate the association between dietary patterns and T2DM, as well as the role played by MUO and oxidative stress in influencing inflammation and increasing the risk of MetS and, eventually, T2DM.
Article
Current guidelines for obesity treatment recommend reducing daily caloric intake for weight loss. However, long-term weight loss continues to be an issue in obesity management. Alternative weight loss strategies have increased in popularity, such as intermittent energy restriction (IER), a type of eating pattern with periods of fasting alternating with unrestricted eating. The effects of IER on weight loss, cardiovascular risk factors, inflammation, and appetite are not clear. The purpose of this systematic review was to analyze short- (<24 weeks) and long-term (≥24 weeks) effects of IER on anthropometric, cardiometabolic, inflammatory, and appetite outcomes in adults with overweight/obesity. PubMed, CINAHL, Embase, and PsycInfo were searched from inception to July 2020. Human randomized controlled trials (RCTs) on IER with participants with a body mass index ≥25 kg/m ² were included in this review. A total of 42 articles (reporting on 27 different RCTs) were included. In short-term studies, IER showed pre-to-post treatment improvements in eight of nine studies that assessed weight. Weight outcomes were sustained in the long-term. However, no significant long-term between group differences were observed in fat mass, other anthropometric, cardiometabolic, inflammatory, or appetite outcomes. Compared to continuous energy restriction (CER), IER showed no significant long-term differences in anthropometric, cardiometabolic, inflammatory, or appetite outcomes in included studies. More long-term studies are needed to assess the benefits of IER on health outcomes.
Article
Background The high prevalence of obesity and associated comorbidities requires innovative therapeutic approaches for sustainable weight management.Objectives The purpose of this article is to review current and potential future therapy options for weight loss.Materials and methodsThe present work is based on a current selective literature search in the PubMed database.ResultsDiet-induced hormonal changes may be an indicator of cardiometabolic health after weight loss. Effects on body composition and energy intake vary depending on the dietary intervention. In addition to GLP-1-based (GLP-1: glucagon-like peptide 1) therapies that may also contribute to post-bariatric weight loss, new molecules are in development that may represent promising and well-tolerated complementary therapeutic options. Metabolic-bariatric surgery may contribute to a relevant reduction in long-term mortality in patients with obesity and type 2 diabetes mellitus (T2D) as part of an escalating stepwise approach.Conclusions Obesity is a complex health problem due to a combination of causes and individual factors. Strategies for successful weight loss and long-term weight maintenance include new nutritional approaches and pharmacotherapy, including the development of molecules with novel mechanisms of action. For patients with obesity and T2D, metabolic-bariatric surgery may be an effective and safe long-term treatment option.
Article
Intermittent fasting (IF) is a dietary strategy in which a person alternates periods in which he or she eats and does not eat; it should be differentiated from just regular eating because the periods between eating are long enough to make the body switch from hepatocyte‐based glucose metabolism to adipose‐cell‐based ketone metabolism This article is protected by copyright. All rights reserved.
Article
Intermittent fasting diets have become very popular in the past few years, as they can produce clinically significant weight loss. These diets can be defined, in the simplest of terms, as periods of fasting alternating with periods of eating. The most studied forms of intermittent fasting include: alternate day fasting (0-500 kcal per 'fast day' alternating with ad libitum intake on 'feast days'); the 5:2 diet (two fast days and five feast days per week) and time-restricted eating (only eating within a prescribed window of time each day). Despite the recent surge in the popularity of fasting, only a few studies have examined the health benefits of these diets in humans. The goal of this Review is to summarize these preliminary findings and give insights into the effects of intermittent fasting on body weight and risk factors for cardiometabolic diseases in humans. This Review also assesses the safety of these regimens, and offers some practical advice for how to incorporate intermittent fasting diets into everyday life. Recommendations for future research are also presented.
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Intermittent fasting, whose proposed benefits include the improvement of lipid profile and the body weight loss, has gained considerable scientific and popular repercussion. This review aimed to consolidate studies that analyzed the lipid profile in humans before and after intermittent fasting period through a detailed review; and to propose the physiological mechanism, considering the diet and the body weight loss. Normocaloric and hypocaloric intermittent fasting may be a dietary method to aid in the improvement of the lipid profile in healthy, obese and dyslipidemic men and women by reducing total cholesterol, LDL, triglycerides and increasing HDL levels. However, the majority of studies that analyze the intermittent fasting impacts on the lipid profile and body weight loss are observational based on Ramadan fasting, which lacks large sample and detailed information about diet. Randomized clinical trials with a larger sample size are needed to evaluate the IF effects mainly in patients with dyslipidemia.
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Objective: To examine the effectiveness of intermittent energy restriction in the treatment for overweight and obesity in adults, when compared to usual care treatment or no treatment. Introduction: Intermittent energy restriction encompasses dietary approaches including intermittent fasting, alternate day fasting, and fasting for two days per week. Despite the recent popularity of intermittent energy restriction and associated weight loss claims, the supporting evidence base is limited. Inclusion criteria: This review included overweight or obese (BMI ≥25 kg/m) adults (≥18 years). Intermittent energy restriction was defined as consumption of ≤800 kcal on at least one day, but no more than six days per week. Intermittent energy restriction interventions were compared to no treatment (ad libitum diet) or usual care (continuous energy restriction ∼25% of recommended energy intake). Included interventions had a minimum duration of 12 weeks from baseline to post outcome measurements. The types of studies included were randomized and pseudo-randomized controlled trials. The primary outcome of this review was change in body weight. Secondary outcomes included: i) anthropometric outcomes (change in BMI, waist circumference, fat mass, fat free mass); ii) cardio-metabolic outcomes (change in blood glucose and insulin, lipoprotein profiles and blood pressure); and iii) lifestyle outcomes: diet, physical activity, quality of life and adverse events. Methods: A systematic search was conducted from database inception to November 2015. The following electronic databases were searched: MEDLINE, Embase, CINAHL, Cochrane Library, ClinicalTrials.gov, ISRCTN registry, and anzctr.org.au for English language published studies, protocols and trials. Two independent reviewers evaluated the methodological quality of included studies using the standardized critical appraisal instruments from the Joanna Briggs Institute. Data were extracted from papers included in the review by two independent reviewers using the standardized data extraction tool from the Joanna Briggs Institute. Effect sizes were expressed as weighted mean differences and their 95% confidence intervals were calculated for meta-analyses. Results: Six studies were included in this review. The intermittent energy restriction regimens varied across studies and included alternate day fasting, fasting for two days, and up to four days per week. The duration of studies ranged from three to 12 months. Four studies included continuous energy restriction as a comparator intervention and two studies included a no treatment control intervention. Meta-analyses showed that intermittent energy restriction was more effective than no treatment for weight loss (-4.14 kg; 95% CI -6.30 kg to -1.99 kg; p ≤ 0.001). Although both treatment interventions achieved similar changes in body weight (approximately 7 kg), the pooled estimate for studies that investigated the effect of intermittent energy restriction in comparison to continuous energy restriction revealed no significant difference in weight loss (-1.03 kg; 95% CI -2.46 kg to 0.40 kg; p = 0.156). Conclusions: Intermittent energy restriction may be an effective strategy for the treatment of overweight and obesity. Intermittent energy restriction was comparable to continuous energy restriction for short term weight loss in overweight and obese adults. Intermittent energy restriction was shown to be more effective than no treatment, however, this should be interpreted cautiously due to the small number of studies and future research is warranted to confirm the findings of this review.
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Purpose of review: Obesity and obesity-related diseases, largely resulting from urbanization and behavioral changes, are now of global importance. Energy restriction, though, is associated with health improvements and increased longevity. We review some important mechanisms related to calorie limitation aimed at controlling of metabolic diseases, particularly diabetes. Recent findings: Calorie restriction triggers a complex series of intricate events, including activation of cellular stress response elements, improved autophagy, modification of apoptosis, and alteration in hormonal balance. Intermittent fasting is not only more acceptable to patients, but it also prevents some of the adverse effects of chronic calorie restriction, especially malnutrition. There are many somatic and potentially psychologic benefits of fasting or intermittent calorie restriction. However, some behavioral modifications related to abstinence of binge eating following a fasting period are crucial in maintaining the desired favorable outcomes.
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Intermittent fasting (IF), a periodic energy restriction, has been shown to provide health benefits equivalent to prolonged fasting or caloric restriction. However, our understanding of the underlying mechanisms of IF-mediated metabolic benefits is limited. Here we show that isocaloric IF improves metabolic homeostasis against diet-induced obesity and metabolic dysfunction primarily through adipose thermogenesis in mice. IF-induced metabolic benefits require fasting-mediated increases of vascular endothelial growth factor (VEGF) expression in white adipose tissue (WAT). Furthermore, periodic adipose-VEGF overexpression could recapitulate the metabolic improvement of IF in non-fasted animals. Importantly, fasting and adipose-VEGF induce alternative activation of adipose macrophage, which is critical for thermogenesis. Human adipose gene analysis further revealed a positive correlation of adipose VEGF-M2 macrophage-WAT browning axis. The present study uncovers the molecular mechanism of IF-mediated metabolic benefit and suggests that isocaloric IF can be a preventive and therapeutic approach against obesity and metabolic disorders.
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This systematic review synthesized the available evidence on the effect of short-term periods of intermittent energy restriction (weekly intermittent energy restriction; ≥7-d energy restriction) in comparison with usual care (daily continuous energy restriction), in the treatment of overweight and obesity in adults. Six electronic databases were searched from inception to October 2016. Only randomized controlled trials of interventions (≥12 weeks) in adults with overweight and obesity were included. Five studies were included in this review. Weekly intermittent energy restriction periods ranged from an energy intake between 1757 and 6276 kJ/d⁻¹. The mean duration of the interventions was 26 (range 14 to 48) weeks. Meta-analysis demonstrated no significant difference in weight loss between weekly intermittent energy restriction and continuous energy restriction post-intervention (weighted mean difference: −1.36 [−3.23, 0.51], p = 0.15) and at follow-up (weighted mean difference: −0.82 [−3.76, 2.11], p = 0.58). Both interventions achieved comparable weight loss of >5 kg and therefore were associated with clinical benefits to health. The findings support the use of weekly intermittent energy restriction as an alternative option for the treatment of obesity. Currently, there is insufficient evidence to support the long-term sustainable effects of weekly intermittent energy restriction on weight management.
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Background/objectives: The MATADOR (Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound) study examined whether intermittent energy restriction (ER) improved weight loss efficiency compared with continuous ER and, if so, whether intermittent ER attenuated compensatory responses associated with ER. Subjects/methods: Fifty-one men with obesity were randomised to 16 weeks of either: (1) continuous (CON), or (2) intermittent (INT) ER completed as 8 × 2-week blocks of ER alternating with 7 × 2-week blocks of energy balance (30 weeks total). Forty-seven participants completed a 4-week baseline phase and commenced the intervention (CON: N=23, 39.4±6.8 years, 111.1±9.1 kg, 34.3±3.0 kg( )m(-2); INT: N=24, 39.8±9.5 years, 110.2±13.8 kg, 34.1±4.0 kg( )m(-2)). During ER, energy intake was equivalent to 67% of weight maintenance requirements in both groups. Body weight, fat mass (FM), fat-free mass (FFM) and resting energy expenditure (REE) were measured throughout the study. Results: For the N=19 CON and N=17 INT who completed the intervention per protocol, weight loss was greater for INT (14.1±5.6 vs 9.1±2.9 kg; P<0.001). INT had greater FM loss (12.3±4.8 vs 8.0±4.2 kg; P<0.01), but FFM loss was similar (INT: 1.8±1.6 vs CON: 1.2±2.5 kg; P=0.4). Mean weight change during the 7 × 2-week INT energy balance blocks was minimal (0.0±0.3 kg). While reduction in absolute REE did not differ between groups (INT: -502±481 vs CON: -624±557 kJ d(-1); P=0.5), after adjusting for changes in body composition, it was significantly lower in INT (INT: -360±502 vs CON: -749±498 kJ d(-1); P<0.05). Conclusions: Greater weight and fat loss was achieved with intermittent ER. Interrupting ER with energy balance 'rest periods' may reduce compensatory metabolic responses and, in turn, improve weight loss efficiency.International Journal of Obesity advance online publication, 19 September 2017; doi:10.1038/ijo.2017.206.
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Background & aims: Long-term adherence to conventional weight-loss diets is limited while intermittent fasting has risen in popularity. We compared the effects of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk factors in adults with abdominal obesity and ≥1 additional component of metabolic syndrome. Methods & results: In total 112 participants (men [50%] and women [50%]) aged 21-70 years with BMI 30-45 kg/m2 (mean 35.2 [SD 3.7]) were randomized to intermittent or continuous energy restriction. A 6-month weight-loss phase including 10 visits with dieticians was followed by a 6-month maintenance phase without additional face-to-face counselling. The intermittent energy restriction group was advised to consume 400/600 kcal (female/male) on two non-consecutive days. Based on dietary records both groups reduced energy intake by ∼26-28%. Weight loss was similar among participants in the intermittent and continuous energy restriction groups (8.0 kg [SD 6.5] versus 9.0 kg [SD 7.1]; p = 0.6). There were favorable improvements in waist circumference, blood pressure, triglycerides and HDL-cholesterol with no difference between groups. Weight regain was minimal and similar between the intermittent and continuous energy restriction groups (1.1 kg [SD 3.8] versus 0.4 kg [SD 4.0]; p = 0.6). Intermittent restriction participants reported higher hunger scores than continuous restriction participants on a subjective numeric rating scale (4.7 [SD 2.2] vs 3.6 [SD 2.2]; p = 0.002). Conclusions: Both intermittent and continuous energy restriction resulted in similar weight loss, maintenance and improvements in cardiovascular risk factors after one year. However, feelings of hunger may be more pronounced during intermittent energy restriction. Trial registration: www.clinicaltrials.govNCT02480504.
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Objective: Objective: Intermittent fasting (IF) is a term used to describe a variety of eating patterns in which no or few calories are consumed for time periods that can range from 12 hours to several days, on a recurring basis. This review is focused on the physiological responses of major organ systems, including the musculoskeletal system, to the onset of the metabolic switch: the point of negative energy balance at which liver glycogen stores are depleted and fatty acids are mobilized (typically beyond 12 hours after cessation of food intake). Results and conclusions: Emerging findings suggest that the metabolic switch from glucose to fatty acid-derived ketones represents an evolutionarily conserved trigger point that shifts metabolism from lipid/cholesterol synthesis and fat storage to mobilization of fat through fatty acid oxidation and fatty acid-derived ketones, which serve to preserve muscle mass and function. Thus, IF regimens that induce the metabolic switch have the potential to improve body composition in overweight individuals. Moreover, IF regimens also induce the coordinated activation of signaling pathways that optimize physiological function, enhance performance, and slow aging and disease processes. Future randomized controlled IF trials should use biomarkers of the metabolic switch (e.g., plasma ketone levels) as a measure of compliance and of the magnitude of negative energy balance during the fasting period.
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While activation of beige thermogenesis is a promising approach for treatment of obesity-associated diseases, there are currently no known pharmacological means of inducing beiging in humans. Intermittent fasting is an effective and natural strategy for weight control, but the mechanism for its efficacy is poorly understood. Here, we show that an every-other-day fasting (EODF) regimen selectively stimulates beige fat development within white adipose tissue and dramatically ameliorates obesity, insulin resistance, and hepatic steatosis. EODF treatment results in a shift in the gut microbiota composition leading to elevation of the fermentation products acetate and lactate and to the selective upregulation of monocarboxylate transporter 1 expression in beige cells. Microbiota-depleted mice are resistance to EODF-induced beiging, while transplantation of the microbiota from EODF-treated mice to microbiota-depleted mice activates beiging and improves metabolic homeostasis. These findings provide a new gut-microbiota-driven mechanism for activating adipose tissue browning and treating metabolic diseases.