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Background: It is unknown whether short sleep duration causatively contributes to weight gain. Studies investigating effects of partial sleep deprivation (PSD) on energy balance components report conflicting findings. Our objective was to conduct a systematic review and meta-analysis of human intervention studies assessing the effects of PSD on energy intake (EI) and energy expenditure (EE). Design: Embase, Medline, Cochrane CENTRAL, Web of Science and Scopus were searched. Differences in EI and total EE following PSD compared to a control condition were generated using the inverse variance method with random-effects models. Secondary outcomes included macronutrient distribution and resting metabolic rate. Heterogeneity was quantified with the I^2 statistic. Results: Seventeen studies (n = 496) were eligible for inclusion in the systematic review, and eleven studies (n = 172) provided sufficient data to be included in meta-analyses. EI was significantly increased by 384 kcal [95% CI 252, 517], (P < 0.00001) following PSD compared to the control condition. We found no significant change in total EE or resting metabolic rate as a result of PSD. The observed increase in EI was accompanied by significantly higher fat and lower protein intakes, but no effect on carbohydrate intake. Conclusion: The pooled effects of the studies with extractable data indicated that PSD resulted in increased EI with no effect on EE, leading to a net positive energy balance, which in the long term may contribute to weight gain.
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ORIGINAL ARTICLE
The effects of partial sleep deprivation on energy balance:
a systematic review and meta-analysis
HK Al Khatib
1
, SV Harding
1
, J Darzi
1,3
and GK Pot
1,2,3
BACKGROUND/OBJECTIVES: It is unknown whether short sleep duration causatively contributes to weight gain. Studies
investigating effects of partial sleep deprivation (PSD) on energy balance components report conicting ndings. Our objective was
to conduct a systematic review and meta-analysis of human intervention studies assessing the effects of PSD on energy intake (EI)
and energy expenditure (EE).
SUBJECTS/METHODS: EMBASE, Medline, Cochrane CENTRAL, Web of Science and Scopus were searched. Differences in EI and total
EE following PSD compared with a control condition were generated using the inverse variance method with random-effects
models. Secondary outcomes included macronutrient distribution and resting metabolic rate. Heterogeneity was quantied with
the I
2
-statistic.
RESULTS: Seventeen studies (n= 496) were eligible for inclusion in the systematic review, and 11 studies (n= 172) provided
sufcient data to be included in meta-analyses. EI was signicantly increased by 385 kcal (95% condence interval: 252, 517;
Po0.00001) following PSD compared with the control condition. We found no signicant change in total EE or resting metabolic
rate as a result of PSD. The observed increase in EI was accompanied by signicantly higher fat and lower protein intakes, but no
effect on carbohydrate intake.
CONCLUSIONS: The pooled effects of the studies with extractable data indicated that PSD resulted in increased EI with no effect on
EE, leading to a net positive energy balance, which in the long term may contribute to weight gain.
European Journal of Clinical Nutrition advance online publication, 2 November 2016; doi:10.1038/ejcn.2016.201
INTRODUCTION
The current National Sleep Foundation guidelines recommend
79 h of sleep per night for adults aged 1864 years, and state
o6 h may compromise health and well-being.
1
Some evidence
suggests that the average human sleep duration has faced rapid
declines over the past century;
2
however, other data report no
signicant changes.
3,4
Social demands of the busy modern
lifestyle, including excessive screen time and shift work, are
hypothesised to contribute to causing the possible reductions in
sleep duration as well as potential circadian misalignment.
57
The
denition of short sleep duration differs widely across studies
conducted in adults, and varies from 4h
8
to o8h.
9
Despite this
lack of standardisation, most observational data suggests that it is
strongly associated with weight gain and non-communicable
diseases,
1014
yet there remain to be conicts in the evidence.
15,16
Experimental evidence has examined causality of the possible
relationship between short sleep duration and risk of weight gain.
Intervention studies examining the effects of partial sleep
deprivation (PSD), dened as restricted but not complete
elimination of sleep, compared with habitual sleep on energy
balance are thus far equivocal. It remains unknown whether PSD is
causal in weight gain, and if this arises from an excess energy
intake (EI), reduced total energy expenditure (EE) or a combination
of the two factors. A recent systematic review of randomised
controlled trials (RCTs) suggested that restricted sleep may
increase dietary intake; however, the extent of this increase was
not quantied.
17
Understanding the mechanisms associating
weight gain and PSD has the potential to provide a novel target
for intervention in weight management. To the best of our
knowledge, the literature investigating effects of PSD on EI and EE
have not previously been systematically evaluated and quantita-
tively analysed by meta-analysis. Therefore, we aimed to system-
atically review and meta-analyse the effects of PSD on
components of the energy balance equation including EI and
total EE, as well as macronutrient distribution and resting
metabolic rate (RMR) in comparison with habitual sleep in healthy
adults.
MATERIALS AND METHODS
We conducted a comprehensive search on ve databases, Medline,
EMBASE, Cochrane CENTRAL, Scopus and Web of Science, searching all
years of record until 17 November 2014 with no language restrictions. We
also searched reference lists of relevant literature, and for unpublished
studies at http://www.clinicaltrials.gov. Search terms were determined in
collaboration with all the authors through exploration of key words in the
literature. The search terms included Energy Balance,orEnergy Intake,or
Energy Expenditure,orResting Metabolic Rateand Sleep Deprivation
and Sleep Curtailment. For the complete search strategy, please see the
Supplementary Material online. A study protocol was prepared in line with
Cochrane
18
and PRISMA
19
guidelines and registered with International
Prospective Register of Systematic Reviews (PROSPERO) (Registration
Number: CRD42014014978).
1
Diabetes and Nutritional Sciences Division, School of Life Sciences and Medicine, Kings College London, London, UK and
2
VU University Amsterdam, Health and Life, Faculty of
Earth and Life Sciences, Amsterdam, Netherlands. Correspondence: Dr GK Pot, Diabetes and Nutritional Sciences Division, Kings College London, Franklin-Wilkins Building,
150 Stamford Street, London SE1 9NH, UK.
E-mail: gerda.pot@kcl.ac.uk
3
These authors contributed equally to this work.
Received 20 April 2016; revised 18 August 2016; accepted 10 September 2016
European Journal of Clinical Nutrition (2016), 111
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved 0954-3007/16
www.nature.com/ejcn
Study inclusion and exclusion criteria
We included studies assessing healthy male and/or female human
participants with no diagnosed chronic diseases or sleep conditions of
all body mass index (BMI) ranges, aged 18 years. Laboratory-based or
free-living interventional studies were included if they assessed the effect
of PSD, where sleep duration was shortened compared with habitual sleep,
but not eliminated completely, on energy balance. The minimum and
maximum number of hours of sleep for the PSD condition was not
prespecied, as the literature from observational studies provides no
consensus on the denition of short sleep duration. Acute and chronic
studies of PSD were considered. Eligible studies were required to include at
least one night of normal or habitual sleep opportunity allowing longer
duration of sleep than the PSD condition as control or baseline. The
primary outcomes of this review were 24-h total EI, ad libitum EI and 24-h
total EE. Secondary outcomes included macronutrient (protein, carbohy-
drate and fat) intakes and RMR.
We excluded total sleep deprivation interventions, as effects of complete
elimination of sleep were likely to be exaggerated and unrepresentative of
shortened sleep duration. We also excluded fragmented sleep studies as
the effects pertain to disrupted sleep quality, and not duration. Studies
being conducted alongside any other intervention such as weight loss
diets/exercise regimens were excluded as the effects may interfere with
the outcomes of interest.
Study designs
Randomised and non-randomised interventional studies of parallel,
crossover or prepoststudy design were considered eligible. Prepost
studies assessed changes from baseline, and for these studies we treated
the baseline condition as control. We included studies reported in full-text
journal articles as well as conference abstracts. Observational studies,
reviews, meta-analyses and editorials were excluded.
Data extraction and quality assessment
Two reviewers (HA and either JD, GP or SH) independently screened titles
and abstracts of the identied studies for formal review and analysis. The
primary author (HA) retrieved full texts for those identied studies and
extracted the data. Clarication from an independent reviewer (JD, GP or
SH) was sought when required. The data extraction form was designed
based on guidelines from Cochrane,
18
and included authors name and
year, country, research setting (laboratory or free-living), study design,
number of participants, sex, age, BMI, length of treatment, number of
hours of sleep in the PSD condition, number of hours of sleep in the
control/baseline condition and methods of assessment of sleep, EI and EE.
Data from multiple reports of the same study, including journal articles and
abstracts, were collated under a single study identier, and referenced
under the main full-text article.
Means and s.d. or s.e.m. for daily EI (kcal or kJ), EE (kcal or kJ) and/or
macronutrients for the PSD and control conditions were to be reported for
inclusion in the meta-analysis. Where s.e.m. was reported, s.d. was
calculated for inclusion in the meta-analysis. Macronutrients were to be
reported as a percentage of total energy consumed (%E) to allow for the
comparison of macronutrient distribution. When means and s.d. or s.e.m.
were not reported (kcal or kJ) in tables or text, as well as when
macronutrients were reported in grams, and not %E for macronutrients,
attempts were made to contact the corresponding authors for clarication
on full-text articles by email, twice in 1 month. If the data were unavailable
when authors were contacted, but was presented in a gure, we extracted
the data using a visual screen ruler. The primary reviewer (HA) assessed the
quality of included studies by using the Cochrane Risk of Bias assessment
tool.
20
Statistical analysis
Statistical analyses were conducted in Review Manager 5.2 (Copenhagen,
Denmark) software. We calculated the raw mean difference, and used the
inverse variance method to weight the studies, and pooled data using the
random-effects model to quantify difference in means. We tested for
between-study heterogeneity using the Q-statistic, and quantied its
extent using I
2
-statistic.
21
A sensitivity analysis was performed to separate
effects of study design (RCT, non-randomised and prepost) as pre-
specied. Publication bias was assessed subjectively by visual inspection of
Beggs funnel plot for skewness.
22
AP-value o0.05 was considered
statistically signicant.
RESULTS
Search results
The details of the literature search are presented in Figure 1. We
identied 5843 publications for screening after duplicates were
Figure 1. Flow chart of literature searching, screening and selection of articles for inclusion in this systematic review on the effect of PSD on
energy balance.
1
One study (Spaeth et al
34
) entered twice as means were presented separately for males and females.
2
Data extracted from
gures using visual screen ruler for two studies (Markwald et al
28
, Spaeth et al
34
).
Effect of sleep deprivation on energy balance
HK Al Khatib et al
2
European Journal of Clinical Nutrition (2016) 1 11 © 2016 Macmillan Publishers Limited, part of Springer Nature.
removed. Of these, 86 were retrieved in full text for further in-
depth evaluation, from which a total of 28 publications reporting
on 16 studies including 496 subjects were identied as suitable for
inclusion. Multiple publications reporting on a single study were
identied and combined under the main journal articlesrst
authors name and year of publication, as outlined in Table 1.
Twelve of the publications were full-text articles reporting on 11
studies.
2334
Seven of these studies
2426,28,3234
were associated
with 11 conference abstracts.
3545
A further ve studies were
reported in ve conference abstracts, with no full-text articles
identied,
4650
which were thus treated as stand-alone abstracts.
Characteristics of included studies
An overview of the characteristics of studies included in this article
is presented in Table 2.
Design. Ten randomised crossover studies,
24,25,27,29,32,4650
two
non-randomised crossover studies,
28,30
two randomised parallel
studies
26,33
and two prepost design studies
23,34
were included in
the present review. The length of the wash-out period in the 10
randomised controlled crossover studies ranged from 5 days
51
to 3 months.
29
Most studies were conducted in the laboratory
setting,
24,2629,3234,46,49
two were a combination of laboratory
setting and free-living,
25,30
and only two were entirely free-
living.
23,48
The interventions were generally of a short duration,
with o1 week spent in the PSD and control conditions in 14
studies,
2325,27,28,30,3234,4650
and the longest intervention being
2 weeks per condition.
29
Three studies were acute, assessing each
condition for only one night.
25,48,50
The most severe PSD studies
restricted sleep duration to 3 h 30 min or o4 hs per night.
47,50
In
the least restrictive interventions, PSD sleep was restricted to 5 h
30 min,
29
or to two-thirds of participantshabitual sleep.
26
The
method of sleep restriction varied such that participants had
different sleep midpoints between studies. Five studies kept the
wake point constant and delayed bedtime,
26,27,30,33,34
and ve
studies shifted wake time and sleep time closer together, evading
shifts in sleep midpoints.
24,25,28,29,32
However, six studies did not
report bed times and wake times.
23,4650
The prescribed time in
bed for the control condition varied across studies from 7 h
47
to
10 or 12 h.
34
Participant characteristics. The 16 studies included 222 males and
244 females, with the sex of the remaining 30 unreported.
49,50
Participantsage ranged from 18 to 50 years. Of the studies that
reported participantsBMI, four restricted the sample to partici-
pants within the normal/healthy BMI range,
25,26,28,30
seven
included participants within the overweight range
23,24,27,29,3234
and ve studies included obese participants.
23,27,33,46,48
Of the
studies that included female participants, only two accounted for
the menstrual phase.
29,32
Effect of PSD on EI
Qualitative analysis. Fourteen studies including 480 partici-
pants assessed the effect of PSD on EI, of which 12 studies
(n= 454) reported on mean 24-h EI based on 1 day,
24,25,30,4850
25 days
23,26,28,33,34
or 14 days
29
in the PSD and control conditions
(As shown in Table 2). The reported dietary assessment methods
included dietary records,
23
ad libitum food access from inside and
outside the laboratory
26
or self-selected items from outside the
laboratory.
52
Four studies used a combination of scheduled meals
and ad libitum food access from within the testing facility.
28,29,33,34
Four studies included buffet meals for breakfast,
30,50
lunch,
25
dinner
49
or snack access,
30,49
used in combination with scheduled
meals,
25,30
dietary records
25
or 24-h recall.
50
Two of the
aforementioned studies reported using heterogeneous buffet
settings including 20
25
or 48 items;
30
however, two other studies
did not state whether the buffet was homogeneous or
heterogeneous.
49,50
Two studies reported ad libitum EI from a
single buffet breakfast
46
or lunch,
27
but did not assess total 24-h
EI. Of the 12 studies reporting on total 24-h mean EI, seven
reported a signicantly higher EI in the PSD condition in
comparison with the control condition.
2325,28,33,34,49
The remain-
ing four studies found no signicant difference in EI between the
PSD and control conditions,
26,29,48,50
of which one was the longest
study.
29
The two studies reporting EI from a single buffet meal also
found no signicant difference in EI.
27,46
None of the studies
found a reduction in EI in response to PSD compared with the
control condition.
Quantitative analysis. Sufcient data were only available to
assess quantitatively total 24-h EI. Ten of the 12 studies
assessing total 24-h EI were able to be included in the meta-
analysis.
2326,2830,33,34,49
Two were not included as numbers were
not reported in the conference abstract.
48,50
The studies included
in the meta-analysis comprise of all seven studies reporting an
increase in total 24-h EI, and three of the ve studies with no
effect. Two studiesdata were extracted from gures,
28,34
of which
one study
34
presented male and female data separately, and was
thus entered twice (Spaeth 2014 (m), Spaeth 2014 (f)) into the
meta-analysis to account for this. Overall, the quantitative analysis
included n= 185 and n= 161 subjects in the PSD and control
conditions, respectively. The pooled mean increase in total 24-h EI
in the PSD condition compared with control was 385 kcal (95%
condence interval (CI): 252, 517; Po0.00001), with low hetero-
geneity (Q = 6.28, d.f. = 10, P= 0.79, I
2
= 0%) (Figure 2). A sensitivity
analysis showed that a total 24-h EI was signicantly increased as a
result of PSD in both the randomised
2426,28,29,33,49
(364 kcal
(95% CI: 191, 538; Po0.0001)) and non-randomised studies
23,30,34
(411 kcal (95% CI: 165, 657; P= 0.001)) with low heterogeneity
(PSD: Q = 2.16, d.f. = 6, P= 0.90, I
2
= 0%; Control: Q = 4.00, d.f. = 3,
P= 0.26, I
2
= 25%).
Effect of PSD on EE
Qualitative analysis. Six studies including 87 participants
reported on the effect of PSD on total 24-h EE, measured by
whole-room indirect calorimetry,
28,32,47
heart rate monitor
23
or
doubly labelled water.
24,29
The two studies assessing EE by whole-
room indirect calorimetry showed a signicant increase (~5%) in
EE in response to PSD.
28,32
The four remaining studies found no
signicant difference in EE as a result of PSD.
23,24,29,47
Quantitative analysis. Sufcient data for inclusion in the meta-
analysis were available for ve of the six studies investigating the
effect of PSD on total 24-h EE.
23,24,28,29,32
One study was not
included as the numbers were not reported in the conference
abstract.
47
One studys data were extracted from a gure.
28
The
meta-analysis included n= 73 PSD and n= 73 control participants,
as shown in Figure 3. The studies included the two studies
observing an increase in total 24-h EE as a result of PSD, and three
of the four reporting no effect. There was no signicant change in
24-h EE as a result of PSD (88 kcal; 95% CI: 21, 198; P= 0.11), with
low heterogeneity (Q = 1.08, d.f. = 4, P= 0.90, I
2
= 0%). Exclusion of
the single non-randomised study
23
did not signicantly affect the
results (81 kcal; 95% CI: 30, 193; P= 0.15).
Effect of PSD on macronutrient intake
Qualitative analysis. Of the 14 studies assessing EI, 12 studies
reported on changes in macronutrient intake from mean 24-h
EI
2325,2830,33,34,49,50
or a single buffet meal.
27,46
The PSD condition
was reported to signicantly increase fat intake in four
studies,
24,25,30,34
which one attributed to saturated fat in
particular,
24
and to reduce protein intake in two studies
27,34
compared with control. Carbohydrate intake was signicantly
higher in the PSD condition compared with control in two
Effect of sleep deprivation on energy balance
HK Al Khatib et al
3
© 2016 Macmillan Publishers Limited, part of Springer Nature. European Journal of Clinical Nutrition (2016) 1 11
Table 1. Characteristics of included studies assessing the effect of PSD on energy balance
Author, ref. Setting Study design Participants Intervention duration (n) (time (h/n)) timing Method of assessment
PSD Control Sleep EI EE
Bosy-Westphal et al.
23,a
Free-living, Germany Prepost
No WO
14 F
Age: 2328 years
BMI: 20.036.6 kg/m
2
4 nights (7, 6, 6 and 4 h) 2 nights
48h
Heart rate DR EE: heart rate
RMR: IC-VH
Brondel et al.
25,35,b
Free-living
c
and
lab-setting, France
RCT-CO 5 days
WO
12 M
Age: 1829 years
BMI: 1924.6 kg/m
2
1 night 4 h (02000600 hours) 1 night 8 h (00000800 hours) Waist actim. DR and scheduled meals
and 1 lunch buffet
Calvin et al.
26,70,b
Lab-setting, USA RCT-PL 17 adults (11 M, 6 F)
Age: 1840 years
BMI: 18.524.9 kg/m
2
8 nights (habitual)
Awake at 0600 hours
8 nights ad libitum
Awake at 0600 hours
PSG Ad libitum from kitchen
and outside
Demos et al.
46,
d
Lab-setting RCT-CO 14 adults (2 M, 12 F)
Mean age: 41 years mean
BMI: 32 kg/m
2
1 weekend 5 h 1 weekend
9h
NR Breakfast buffet
All other meals constant
Hart et al.
27
Lab-setting, USA RCT-CO 7 days
WO
12 F
Age: 41.7 ±10.3 years
BMI: 25.838.4 kg/m
2
(17 enrolled, 5 dropout)
2 nights
4or5h
Wake time constant
2 nights
9h
PSG 1 buffet lunch
Not full 24 h
Kubota et al.
47,d
NR RCT-CO 6 M 3 nights
3 h 30 min
4 nights
7h
PSG EE: IC-WR
LeCheminant et al.
48,d
Free-living RCT-CO1 week
WO
22 normal wt F
Age: 30.9 ±9.5 years
BMI: 22.0 ±1.6 kg/m
2
18 obese F,
Age: 29.7 ±10.7 years
BMI: 36.4 ±5.3 kg/m
2
1 night
o5h
1 night
8h
Sleep logs
and WA
Weighed food
Markwald et al.
28,37,b
Lab-setting, USA NRCT-CO
No WO
16 adults
(8 M, 8 F) Age: 22.4 ±4.8
years BMI: 22.9 ±2.4 kg/m
2
5 nights 5 h delay bedtime,
advance wake time
5 nights 9 h habitual bedtime
and wake time
PSG scheduled meals ad
ad libitum snacks
EE: IC-WR
Nedeltcheva et al.
29
Lab-setting, USA RCT-CO 3 months
WO
11 adults (6 M, 5 F
e
)
Age: 3449 years
BMI: 2429.5 kg/m
2
2 weeks 5 h 30 min
Delay bedtime, advance wake
time
2 weeks
8 h 30 min
Habitual bedtime and wake time
EEG scheduled meals and
ad libitum snacks
EE: DLW
RMR: IC
Schmid et al.
30
Free-living
c
and
lab-setting, Germany
NRCT-CO 6 weeks
WO
15 M
Age: 2040 years
BMI: 22.9 ±0.3
2 nights
4 h (02450700 hours)
2 nights
8 h (22450700 hours)
EEG Breakfast buffet, snack
buffet and scheduled
meals
Shechter et al.
32,31,39,b
Lab-setting, USA RCT-CO 4 weeks
WO
10 healthy F
e
Age: 2243 years
BMI: 23.427.5 kg/m
2
(12 enrolled, 2 dropped
out)
3 nights
4 h (01000500 hours)
Includes one night acclimation
3 nights
8 h (23000700 hours)
Includes 1 night acclimation
WA WM EE: IC-WR
RMR: IC-WR
Spaeth et al.
33,4244,b,f
Lab-setting, USA RCT-PL 225 adults (124 M, 101 F)
Age: 2250 years
BMI: 1930 kg/m
2
5 nights
4 h (04000800) n=198
(n=31 with EI data)
5 nights
10 h (22000800 hours) n=27
(n=6 with EI data)
WA Scheduled meals and
ad libitum
Spaeth et al.
34,40,41,45,a,b,f
Lab-setting, USA Prepost
No WO
44 adults (23 M, 21 F)
Age: 2150 years
BMI: 25.2 ±3.5 kg/m
2
(47 enrolled, 3 dropout)
Five nights
4 h (04000800 hours)
2 nights 10 h (22000800 hours)
or 12 h (22001000 hours)
WA Scheduled meals and
ad libitum
St-Onge et al.
24,38,b,f
Lab-setting, USA RCT-CO4 weeks
WO
30 adults (15 M, 15 F)
Age: 3045 years
BMI: 2226 kg/m
2
5 nights 4 h (0100
0500 hours)
Five nights
9 h (22000700 hours)
PSG WM (4 days) ad libitum
Self-selected (days 5 and
6) Included DR day 6
EE: DLW RMR:
IC-VH
Tasali et al.
49,d
NR RCT-CO 10 young lean subjects 4 nights 4 h 30 min 4 nights
8 h 30 min
NR Ad libitum buffet lunch,
dinner, snacks access
Taylor et al.
50,d
Hospital, on-call RCT-CO 20 residents
Age: 32 ±5.6 years
(27 enrolled, 7 dropout)
1 night o4 h 1 night 48 h NR Breakfast buffet
and 24 h recall
Abbreviations: DLW, doubly labelled water; DR, dietary records; EE, energy expenditure; EEG, electroencephalography; EI, energy intake; GIT, h/n, hours per night; ICVH, indirect calorimetryventilated hood; IC
WR, indirect calorimetrywhole room; n, nights; NR, not reported; NRCT-CO, non-randomised controlled trial-crossover; , not assessed; PSD, partial sleep deprivation; PSG, polysomnography; RMR, resting
metabolic rate; RCT-CO, randomised controlled trial-crossover; RCT-PL, randomised controlled trial-parallel; WA, wrist actigraphy; waist actim., waist actimetr y; WM, weight maintenance; WO, washout; wt,
weight.
a
Prepost: baseline measurements compared with intervention.
b
Conference abstract associated with journal article.
c
At least one day time spent free-living..
d
Stand-alone conference abstract.
e
Females
were in the same phase of their menstrual cycle for control and intervention phases.
f
Outcomes for meta-analysis provided when contacted.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
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European Journal of Clinical Nutrition (2016) 1 11 © 2016 Macmillan Publishers Limited, part of Springer Nature.
studies.
28,49
However, no signicant changes in macronutrient
intakes were found in six studies.
23,27,29,33,46,50
None of the studies
reported decreased carbohydrate, decreased fat or increased
protein intakes in the PSD condition compared with control.
Quantitative analysis. Of the 10 studies reporting on %E for
macronutrient intakes, seven studies provided sufcient data for
inclusion in the meta-analyses,
2325,29,30,33,34
including n= 151 and
n= 126 subjects in the PSD and control conditions, respectively.
Three studies were not included as the numbers were not
reported in the conference abstract,
49,50
or data were reported in
grams and were unavailable when authors were contacted.
28
Fat
intake was 1.6%E (95% CI: 0.3, 2.9; P= 0.02) higher in the PSD
condition compared with control with low heterogeneity
Table 2. Results of studies assessing the effect of PSD on energy balance
Author, ref. Sleep duration EI EE
Control PSD Days analysed
Bosy-Westphal et al.
23,a
9h1min±57 min 5 h 29 min ±35 min 3 days baseline
4 days PSD
EI compared
with baseline
Δmacronutrient
distribution: NS
ΔEE: NS
ΔRMR: NS
Brondel et al.
25,35,b,c
7 h 14 min ±40 min 3 h 46 min ±14 min 1 day EI
fat
Calvin et al.
26,70,c
6 h 57 min (SD NR) 5 h 12 min (SD NR) 2 days baseline and
last 2 days PSD
ΔEI: NS between
PSD
and control
groups
EI compared
with baseline in
PSD group
Demos et al.
46,d
NR NR 1 buffet meal ΔEI: NS
Δmacronutrient
distribution: NS
Hart et al.
27
7 h 26 min ±14 min 4 h 21 min ±23 min 1 buffet lunch
Not 24 h
ΔEI: NS
protein
Kubota et al.
47,d
NR NR ΔEE: NS
LeCheminant et al.
48,d
7 h 42 min ±18 min 4 h 42 min ±24 min 1 day (lunch, dinner,
after dinner)
ΔEI: NS
Markwald et al.
28,37,c
7 h 41 min ±42.6 min 4 h 40 ±10.1 min 5 days EI
carbohydrate
EE
Nedeltcheva et al.
29
7 h 13 min 5 h 11 min 14 days ΔEI: NS
Δmacronutrient
distribution: NS
ΔEE: NS
ΔRMR: NS
Schmid et al.
30,b
Night 1: 7 h
45 min ±4 min Night
2: 7 h 47 min ±3 min
Night 1: 3 h
56 min ±1 min Night
2: 3 h 58 min ±1 min
1 day breakfast
buffet, snack buffet
and main meals
ΔEI: NS
fat
Shechter et al.
31,32,39,c
7 h 21 min ±5.1 min 3 h 44 min ±2.2 min WM EE
ΔEE during scheduled sleep
episodes and across waking
period: NS
ΔRMR: NS
Spaeth et al.
33,42,44,c,f
NR NR 2 days baseline,
5 days PSD
EI
Δmacronutrient
distribution: NS
Spaeth et al.
34,40,41,45,a,c,f
NR NR 2 days baseline,
3 days PSD
EI compared
with baseline
fat
protein
St-Onge et al.
24,38,c,f
7 h 38 min ±38.2 min 3 h 46 min ±38.2 min 1 day (4 days before
were WM)
EI
fat and
saturated fat
intake
ΔEE: NS
ΔRMR: NS
Tasali et al.
49,d
7 h 54 min 4 h 24 min 1 day EI
carbohydrate
Taylor et al.
50,d
NR NR 1 day ΔEI: NS
Δmacronutrient
distribution: NS
Abbreviations: Δ, change; DR, dietary records; EE, energy expenditure; EI, energy intake; NR: not reported; NS, not signicant; , not assessed; PSD, partial
sleep deprivation; PSQ, polysomnography; RMR, resting metabolic; WM, weight maintenance.
a
Pre-post: baseline measurements compared with intervention;
b
At least one day time spent free-living.
c
Conference abstract associated with journal article.
d
Stand-alone conference abstract.
e
Females were in the same
phase of their menstrual cycle for control and inter vention phases.
f
Outcomes for meta-analysis provided when contacted.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
5
© 2016 Macmillan Publishers Limited, part of Springer Nature. European Journal of Clinical Nutrition (2016) 1 11
(Q = 3.45, d.f. = 6, P= 0.75, I
2
= 0%) (Figure 4a). However, signi-
cance was lost when analysed by subgroup of randomised (2.0%E;
95% CI: 0.2, 4.3; P= 0.07) and non-randomised (1.3%E: 95% CI:
0.3, 3.0; P= 0.38) studies. A pooled mean decrease in protein
intake of 0.8%E (95% CI: 1.5, 0.1; P= 0.02) with low
heterogeneity (Q = 1.06, d.f. = 1, P= 0.30, I
2
= 5.2%) was found for
the PSD condition compared with control, as shown in Figure 4b.
A sensitivity analysis showed that the pooled mean decrease was
only signicant in the non-randomised studies (1.0%E; 95% CI:
2.1, 0.0; P= 0.06). As shown in Figure 4c, carbohydrate intake was
not signicantly different between condition in the overall meta-
analysis (0.2%E; 95% CI: 1.7, 1.3; P= 0.08), with low hetero-
geneity (Q = 3.95, d.f. = 6, P= 0.68, I
2
= 0%), and in the subgroup
analyses investigating randomised (0.5%E; 95% CI: 3.1, 2.1
P= 0.69) and non-randomised studies (0.0%E; 95% CI: 1.9,
1.8; P= 0.98).
Effect of PSD on RMR
Qualitative analysis. Four studies including 65 participants
assessed the effects of PSD on RMR.
23,24,29,32
In all the studies,
RMR was measured by a form of indirect calorimetry, including
ventilated hood,
23,24
spirometry
29
or a whole-room indirect
calorimeter.
32
No signicant difference in RMR between condi-
tions was detected.
23,24,29,32
Quantitative analysis. Four studies including n= 61 in the PSD
and n= 61 in the control groups provided sufcient data for
inclusion in the meta-analysis investigating the effect of PSD on
RMR.
23,24,29,32
The pooled mean difference in RMR between the
PSD and control conditions was statistically nonsignicant (8 kcal
per day; 95% CI: 62, 46; P= 0.77), with low heterogeneity (Q=1.2,
d.f. = 3, P= 0.75, I
2
= 0%) (Figure 5). This lack of signicant effect
remained in a subgroup analysis including only the randomised
studies
24,29,32
(16 kcal per day; 95% CI: 79, 48; P= 0.63).
Quality assessment and risk of bias
Of the randomised studies,
2427,29,32,33
only one disclosed the
method of random sequence generation and were thus at low risk
of selection bias
26
(Figure 6). All studies were at unclear risk of
selection bias as allocation concealment was unreported. As these
are sleep intervention studies, it is impossible to blind participants
to treatment, which may inuence performance bias. However,
Figure 2. Forest plot of the difference in 24-h total EI changes after PSD in control and intervention groups.
Figure 3. Forest plot of the difference in 24-h total EE changes after PSD in control and intervention groups.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
6
European Journal of Clinical Nutrition (2016) 1 11 © 2016 Macmillan Publishers Limited, part of Springer Nature.
two studies reported that participants were unaware of the
outcomes of interest.
25,30
Only one study specied that partici-
pants were aware of their assigned sleep schedule before each
condition, placing it at high risk of bias.
26
One study reported that
outcome assessors were blinded to treatment;
27
all other studies
were at unclear risk of detection bias. All studies reported
Figure 4. (a) Forest plot of the difference in fat intake as a percentage of 24-h total EI changes after PSD in control and intervention groups. (b)
Forest plot of the difference in protein intake as a percentage of 24-h total EI changes after PSD in control and intervention groups. (c) Forest
plot of the difference in carbohydrate intake as a percentage of 24-h total EI changes after PSD in control and intervention groups.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
7
© 2016 Macmillan Publishers Limited, part of Springer Nature. European Journal of Clinical Nutrition (2016) 1 11
outcome data, and were at low risk of attrition bias; however, the
largest study (n= 225) only assessed outcomes in a subset (n=31
PSD, n= 6 control) and did not mention drop-out rates for the
remaining recruited subjects, and was thus at unclear risk of
attrition bias.
33
As original protocols were not available for all
studies, it is difcult to assess if outcomes were selectively
reported. Visual inspection of Beggs funnel plots showed that
publication bias was unlikely; however, the small number of
studies included in the review precludes ascertaining
publication bias.
DISCUSSION
Our ndings from this systematic review and meta-analysis of
intervention studies suggest that PSD may lead to a net positive
energy balance of 385 kcal per day because of a signicant
increase in total 24-h EI, and no effect on total 24-h EE. The
perceived positive energy balance may therefore contribute to the
occurrence of weight gain in those with short sleep duration. Our
ndings also suggest possible modest shifts in macronutrient
distribution, favouring fat intake at the cost of protein. However,
our results are mainly based on studies with highly restrictive
sleep schedules conducted in controlled laboratory conditions
over a short period of time (1 day to 2 weeks). It remains unknown
whether the observed net positive energy balance is evident over
a prolonged period of less restrictive sleep deprivation that
mirrors the effects of chronic sleep debt. In support of our
ndings, a recent systematic review by Capers et al.
17
who studied
the impact of sleep duration on adiposity and components of
energy balance concluded that sleep deprivation appears to
increase food intake. Unlike the present review, Capers et al.
17
did
not perform a meta-analysis for EI owing to the inconsistencies of
methodology to measure food intake in the six RCTs they
identied. However, our meta-analysis suggests the variation in
methods to measure EI did not introduce heterogeneity. Unlike
the present study, Capers et al.
17
found no signicant effects of
sleep restriction on total EE in their meta-analysis. However, in
contrast to the present review, Capers et al.
17
included only RCTs,
considering all forms of manipulation of sleep duration including
total sleep deprivation and sleep extension, and did not exclude
studies in children or adolescents, which could explain the
differences in results obtained.
It has been previously suggested that sleep deprivation may
cause dysregulation of the hormones leptin and ghrelin, leading
to an increase in EI.
17,23,5254
Arguably, a more plausible
explanation for the observed increase in EI after PSD in this
review is that this is hedonically driven. Hedonic inuence was
demonstrated in a crossover RCT in 26 healthy adults in which PSD
resulted in greater neuronal activation in response to food stimuli,
particularly in areas associated with reward.
55
These ndings
suggest that short sleep heighten the motivation to seek food for
reward.
55
Furthermore, a cross-sectional study in 115 healthy,
Figure 5. Forest plot of the difference in RMR (kcal per day) changes after PSD in control and intervention groups.
Figure 6. Review authors judgement on each risk of bias item from the Cochrane Tool for each included study in the systematic review and
meta-analysis assessing the effect of PSD on energy balance.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
8
European Journal of Clinical Nutrition (2016) 1 11 © 2016 Macmillan Publishers Limited, part of Springer Nature.
premenopausal women associated sensitivity to reward with a
greater preference for foods high in fat and sugar.
56
Indeed, our
meta-analysis detects this possible heightened inclination for
intake of fat. Yet, the longest study in the present review (2 weeks)
found an increased consumption of snacks high in carbohydrates
during the PSD condition with no effect on 24-h EI, yet whether
the carbohydrate increase was specically attributed to sugar or
rened carbohydrates was unspecied.
29
Only one study analysed
saturated fat intake separately;
24
this is of importance as in the
long term the type of fat consumed may have serious ramica-
tions on cardiovascular health.
5759
Laboratory-controlled condi-
tions are necessary and valuable; however, free-living conditions
may also provide information that is arguably more representative
of dietary behaviours because of unlimited food choice and
variety; two of the four studies including free-living conditions in
this review report no signicant change in 24-h EI as a result of
PSD,
30,48
of which one reports a signicant increase in fat intake.
30
Moreover, investigating the chronic effects of PSD that is
representative of habitual trends is warranted, as the adaptive
response of sleep debt build-up may be to reshift toward energy
balance, with long-term effects on macronutrient distribution.
We found no signicant change in total 24-h EE; it is possible
that this is because of differences in methods of EE measurements
across studies. The two studies that used whole-room indirect
calorimetry
28,32
found a similar 5% increase in 24-h EE, and this is
in agreement with previous studies conducted in adolescents.
60
Shechter et al.
32
discerned the increase was only evident during
nocturnal hours spent awake. Previous ndings have shown that
the metabolic costs of sleep have been shown to be lower
compared with those of awake time.
6163
Despite the benetof
such accurate measuring techniques, respiratory chambers limit
the ability to depict habitual physical activity owing to conned
living, which is of crucial importance as activity EE is a key
component of total EE. Free-living conditions may provide insight
into the effect of PSD on physical activity and activity EE, and
would illustrate ecologically valid integrated effects of EI and EE.
For example, although Schmid et al.
30
did not report on EE, they
have shown that PSD resulted in decreased physical activity and
intensity, measured by accelerometry. The effects of PSD on
activity EE and physical activity are of importance as this may be
another potential factor linking short sleep and metabolic
consequences. The lack of impact of PSD on RMR observed in
the present review should be interpreted with caution; there was a
small number of studies identied thereby limiting study power.
Moreover, the longest study assessing RMR was 2 weeks long per
condition,
29
and it is possible that this time frame was insufcient
to allow for adaptation of the metabolic rate. Previous observa-
tional evidence reported that measured RMR was signicantly
elevated in chronic insomniacs compared with age-, sex- and
weight-matched normal sleepers at all measured time-points over
a 36-h sleep laboratory stay,
64
warranting further investigation of
RMR after extended periods of PSD.
Strengths and limitations
This review has some notable strengths; it comprehensively and
systematically identied relevant studies, with no search restric-
tions and was conducted in line with the PRISMA statement.
Moreover, two independent reviewers reviewed the titles and
abstracts identied. A methodological limitation of this review is
that not all identied studies could be included in the meta-
analyses; this was a result of the reported data being inextractible
and unavailable when authors were contacted. Because the
majority of PSD studies that observed no effect on total 24-h EI,
our pooled results could possibly overestimate EI. Our limitation
highlights the need for future studies to report accurately ndings
to allow pooling of the data. Moreover, studies reported the
absolute change in kcal and this may be dependent on an
individual, yet the percentage change for EI and EE may not,
emphasising the importance for future studies to also report
percentage changes.
There are also various strengths and limitations related to the
studies included in this review. Many of the included studies were
of a robust randomised crossover design. However, there was
heterogeneity in the interventions, including intervention dura-
tion, degree of sleep restriction, sleep schedule and time in bed in
the control condition. Moreover, EI and EE assessment methods
may have caused discrepancies in results; it is possible that
laboratory-setting studies introduce bias because of the dened
food choices available, and that detection of changes in total EE
was limited by measurement device accuracy. In addition, it has
been previously shown that the female menstrual cycle phase
may impact sleep
65
and components of energy balance;
6669
however, only two studies in this review attempted to account for
this variation in females participants.
28,31
The quality of studies
identied is also a limitation to be considered; the majority of the
studies were at an unclear risk of selection, performance and
detection bias, mainly due to non-disclosure of method of random
assignment, and lack of blinding of assessors.
Last, the external validity of included studies could be
questioned as most studies were performed under experimental
sessions, and included subjects were predominantly of Caucasian
or African-American ethnicity. It should also be noted that the
results of the present review cannot be extended to claim that
extension of sleep would cause a reverse shift in energy balance,
and this remains to be explored.
CONCLUSION
The evidence in the present review suggests that PSD may result
in an increased EI, leading to a net positive energy balance of
385 kcal per day. In the long term, this may implicate weight gain;
however, it remains to be investigated. We found no signicant
change in EE, although this may be attributed to variations in
measurement techniques across studies. Short-term PSD resulted
in no change in RMR, although various studies report that
extended wake time is more energy costly in controlled laboratory
conditions. Further investigation of the effects of PSD on physical
activity and activity EE is warranted. Robustly designed RCTs are
necessary to identify whether mild, chronic PSD also causes shifts
in dietary intake and macronutrient distribution, with a particular
focus on saturated fat and added sugar, as the evidence is scarce.
Our study highlights the evident lack of studies investigating
effects of PSD on energy balance in an ecologically translatable
setting, particularly as free-living conditions are crucial to under-
pin effects on activity levels and food choice. The pragmatic way
forward may be to examine whether sleep extension in habitually
short sleepers can mitigate the observed effects on energy
balance. Our results propose that sleep may be a potential novel
target for weight management in addition to physical activity and
dietary management in the clinical setting.
CONFLICT OF INTEREST
The authors declare no conict of interest.
ACKNOWLEDGEMENTS
The authorsresponsibilities were as follows: GP and JD designed the study, HA, SH,
JD, and GP performed the literature search and the meta-analysis. GP and JD had
primary responsibility for nal content. All authors were substantially involved in the
writing process. All authors read and approved the nal manuscript.
Effect of sleep deprivation on energy balance
HK Al Khatib et al
9
© 2016 Macmillan Publishers Limited, part of Springer Nature. European Journal of Clinical Nutrition (2016) 1 11
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Effect of sleep deprivation on energy balance
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