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Energy Metabolism and Intermittent Fasting: The Ramadan Perspective

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Intermittent fasting (IF) has been gaining popularity as a means of losing weight. The Ramadan fast (RF) is a form of IF practiced by millions of adult Muslims globally for a whole lunar month every year. It entails a major shift from normal eating patterns to exclusive nocturnal eating. RF is a state of intermittent liver glycogen depletion and repletion. The earlier (morning) part of the fasting day is marked by dominance of carbohydrate as the main fuel, but lipid becomes more important towards the afternoon and as the time for breaking the fast at sunset (iftar) gets closer. The practice of observing Ramadan fasting is accompanied by changes in sleeping and activity patterns, as well as circadian rhythms of hormones including cortisol, insulin, leptin, ghrelin, growth hormone, prolactin, sex hormones, and adiponectin. Few studies have investigated energy expenditure in the context of RF including resting metabolic rate (RMR) and total energy expenditure (TEE) and found no significant changes with RF. Changes in activity and sleeping patterns however do occur and are different from non-Ramadan days. Weight changes in the context of Ramadan fast are variable and typically modest with wise inter-individual variation. As well as its direct relevance to many religious observers, understanding intermittent fasting may have implications on weight loss strategies with even broader potential implications. This review examines current knowledge on different aspects of energy balance in RF, as a common model to learn from and also map out strategies for healthier outcomes in such settings.
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Nutrients 2019, 11, 1192; doi:10.3390/nu11051192 www.mdpi.com/journal/nutrients
Review
Energy Metabolism and Intermittent Fasting:
The Ramadan Perspective
Nader Lessan * and Tomader Ali
Imperial College London Diabetes Center (ICLDC), Abu Dhabi, UAE; tfali@icldc.ae
* Correspondence: nlessan@icldc.ae; Tel.: +971-2-4040-519
Received: 18 April 2019; Accepted: 9 May 2019; Published: 27 May 2019
Abstract: Intermittent fasting (IF) has been gaining popularity as a means of losing weight. The
Ramadan fast (RF) is a form of IF practiced by millions of adult Muslims globally for a whole lunar
month every year. It entails a major shift from normal eating patterns to exclusive nocturnal eating.
RF is a state of intermittent liver glycogen depletion and repletion. The earlier (morning) part of the
fasting day is marked by dominance of carbohydrate as the main fuel, but lipid becomes more
important towards the afternoon and as the time for breaking the fast at sunset (iftar) gets closer.
The practice of observing Ramadan fasting is accompanied by changes in sleeping and activity
patterns, as well as circadian rhythms of hormones including cortisol, insulin, leptin, ghrelin,
growth hormone, prolactin, sex hormones, and adiponectin. Few studies have investigated energy
expenditure in the context of RF including resting metabolic rate (RMR) and total energy
expenditure (TEE) and found no significant changes with RF. Changes in activity and sleeping
patterns however do occur and are different from non-Ramadan days. Weight changes in the
context of Ramadan fast are variable and typically modest with wise inter-individual variation. As
well as its direct relevance to many religious observers, understanding intermittent fasting may
have implications on weight loss strategies with even broader potential implications. This review
examines current knowledge on different aspects of energy balance in RF, as a common model to
learn from and also map out strategies for healthier outcomes in such settings.
Keywords: Fast; intermittent; Ramadan; energy expenditure; weight
1. Introduction
Fasting can be defined as the voluntary abstinence from or reduction of some or all food, drink,
or both (absolute) for a period of time lasting typically between 12 hours and 3 weeks i.e., in a short
term, long term/prolonged or an intermittent pattern [1]. Fasting is a common practice in different
religious disciplines, including Islam, Christianity, Judaism and Hinduism. In Islam, the practice
entails abstinence from eating and drinking between dawn and sunset [2]. Fasting is distinct from
starvation, which is a chronic and severe deficiency in caloric energy intake below the level needed
to maintain life.
Health benefits of intermittent fasting have been demonstrated in both randomized controlled
trials and observational studies [3,4]. Caloric restriction (CR) has also been shown to prevent several
chronic degenerative and inflammatory diseases [5] and to prolong life in more primitive species
including Escherichia coli and yeast [6]. In humans, the evidence on the positive effects of CR on
longevity is indirect; for example the increased life expectancy in the Okinawan population, from the
Kyushu Island in Japan, has been attributed at least in part to low calorie intake [7]. Mechanistically,
the effect of CR on longevity has been attributed to fasting-induced modulation of neuroendocrine
systems, hormetic stress responses, increased systemic production of neurotrophic factors, reduced
Nutrients 2019, 11, 1192 2 of 15
mitochondrial oxidative stress, decreased pro-inflammatory cytokine production and insulin
resistance, as well as decreased aging-associated signals and autophagy promotion [5,8,9].
Prolonged fasting has also been associated with positive effects on mood due to the alteration in
physiology at a cellular level via increases in availability of central endogenous neurotransmitters,
endogenous opioids and endocannabinoids [10]. Cancer studies demonstrated that fasting and
fasting-mimicking diets (FMDs) positively promote differential effects in both normal and
malignant cells via reduction in insulin-like growth factor (IGF-1), insulin and glucose with
paralleled increases in ketone bodies [11]. In contrast, negative effects of fasting have been reported
for instance on non-communicable diseases [8,11,12], on changes to sleep patterns, cognitive
function, [13,14] and have also been associated with fluctuations in mood, weight and a plethora of
other changes [15,16].
Fasting is a state of negative energy balance, and as such different fasting regimens have been
used to achieve weight loss, as well as other health benefits. In the context of Muslim Ramadan-type
fasting, changes in energy intake depend on social, cultural and individual factors and can range
from a reduction to an increase in weight [17–19]. Whether this is accompanied by changes in energy
expenditure is not well-known and merits further exploration for its possible implications in weight
loss management strategies in general [20].
This review will be examining current knowledge about different aspects of energy balance in
the context of the Ramadan fast as a commonly practiced model of intermittent fasting. In the
broader context, potential positive implications include the use of for such strategies to help with
weight maintenance, is not weight loss, and thus a multitude of other consequential positive health
benefits. Relevant literature (Tables 1,2) directly and indirectly related to the Ramadan fast,
including short- and long-term fasting and also prolonged and intermittent type fasting will be
explored. In the context of Ramadan, changes in energy dynamics (intake versus expenditure) have
been extrapolated based on our previous quantitative studies, knowledge of physiology and
alterations in energy utilization during feeding and non-feeding periods. The aim of this review is
firstly, to discuss the various aspects influencing energy modulations during Ramadan fasting;
secondly, to shed light on key knowledge gaps in our understanding of energy balance in relation to
changes in both body composition and physiological adaptation in various models of fasting to
include key periods such as the Ramadan fasting period and; lastly, to contribute to the focused
directionality of future studies in key aspects that warrant further detailed investigations.
2. Energy Expenditure (EE)
When body weight is in a relatively stable state, there is equilibrium between energy intake (EI)
and energy expenditure (EE). High EI levels in combination with low EE results in a positive energy
balance and storage of energy, primarily as body fat. Total (daily) Energy Expenditure (TEE) consists
of Resting Metabolic Rate (RMR), Thermic Effects of Food (TEF) and Activity Energy Expenditure
(AEE) [20]. Different components of EE have been reviewed elsewhere [21–24] and will only be
discussed briefly here.
Resting Metabolic Rate (RMR) is the quantity of energy at rest needed to maintain body
temperature, repair internal organs, support cardiac function, maintain ionic gradients across cells,
and support respiration. In most people, this constitutes approximately two-thirds of total energy
expenditure [25]. RMR is influenced by age, sex, body weight, pregnancy, and hormonal status. The
highest rates of energy expenditure per unit of body weight occur during infancy and decline
through childhood. In adult life, the decline continues at approximately 2% per decade because of a
decline in lean body mass. Females have a lower energy expenditure per unit of weight than do
males, probably because of the higher proportion of body fat and less lean body mass in women [26].
Thermic effect of food is the rise in energy expenditure that occurs with food intake [26]. This rise is
in part due to the ‘obligatory’ energy cost of ingestion, digestion, and metabolic processing of
nutrients, and in part due to a ‘facultative’ component arising from the sensory aspects of food and
meal stimulation of the sympathetic nervous system. Different macronutrients have different
thermic effects; protein causes a greater rise in EE than fat or carbohydrates. Although TEF is
Nutrients 2019, 11, 1192 3 of 15
normally a small component of TEE (~10%) it is nonetheless an important component in energy
imbalance states as it is influenced by meal size and composition, the nature of the previous diet,
insulin resistance, physical activity, and ageing influence TEF [27].
Table 1. Energy Expenditure in Ramadan.
Ref. Year Study Cohort
Gender
& Age
(years)
Reported Observations
[14] 2010
Healthy adults 1-week
pre-Ramadan baseline
(BL) as well as first and
second week of
Ramadan (R1) and (R2);
n = 7).
Males;
21 ± 3
SenseWear Pro Armband measurements indicated EE
and METs significantly lower during Ramadan and a
shift in circadian patterns (of body temperature, a
delay in bedtime and an increase in total sleep time
and nap time) during Ramadan. No significant
difference in the number of meals.
[24] 2018
Healthy adults during
Ramadan and
non-Ramadan periods.
RMR (n = 29, 16 female)
Activity (total steps per
day) (n = 11, 5 female);
TEE (n = 10, 5 female).
Female
and
male;
33 ± 9
Indirect calorimetry; (a) activity during and post-
Ramadan; no significant difference, (b) activity
pattern: morning & afternoon significantly lower
during Ramadan. Nocturnal activity was higher
during Ramadan, (c) TEE & RMR during and
post-Ramadan: no significant difference; main factor
influencing TEE was body weight.
[28] 1995
Healthy adults, 2 days
pre-Ramadan (T1); the
2nd day (T2), and the
28th day (T3) of fasting;
& 1 month after, (n =
16).
Female;
25–39
Indirect calorimetry; calculations from metabolic
chamber; REE unchanged during and post-Ramadan,
compared with pre- Ramadan. EE throughout the
circadian cycle was dramatically affected during
fasting with a significant decrease observed from
11am to 5pm during Ramadan. Nightly EE values did
not change significantly.
[29] 2017
Healthy fasting (FAST,
n = 9) and non-fasting
(CNT, n = 8) adults pre
and post-Ramadan.
FAST group
additionally assessed at
days 10, 20 & 30 of
Ramadan (am) & (pm).
Male;
FAST:
32 ± 8
and
CNT:
35 ± 9
Indirect calorimetry; significant group × time
interaction, reduced body mass and adiposity in
FAST, without changing lean mass; for CNT subjects,
remained unchanged. Ramadan fasting induces
diurnal metabolic adjustments (morning v. evening)
with no carryover effect observed throughout
Ramadan fasting despite the extended daily fasting
period and changes in body composition.
Table 2. Energy intake and weight changes during Ramadan.
Ref Year Study Cohort Gender &
Age (years) Reported Observations
[18] 2014
Healthy fasting
adults with normal
body weight; n =
1476; 553 female and
923 male)
Female and
male; 18
In the female subgroup, body weight (SMD = 0.04,
95% CI = 0.20, 0.12) remained unchanged, while in
males, Ramadan fasting resulted in weight loss (SMD
= 0.24, 95% CI = 0.36, 0.12, p = 0.001).
[28] 1995
Healthy fasting
adults, two days
pre-Ramadan (T1);
second (T2) and 28th
day (T3) of Ramadan;
and 1 month
post-Ramadan (T4); n
= 16
Female; 25–
39
Total daily energy intake, body weight, fat mass and
fat free mass remain unchanged. REE pattern change;
lower during the fasting day versus night but no
significant change overall.
[29] 2017
Healthy fasting
(FAST, n = 9) and
non-fasting (CNT, n =
8) adults pre and
post-Ramadan. FAST
group additionally
assessed at days 10,
20 & 30 of Ramadan
both (am) and (pm).
Male;
FAST: 32 ±
8, CNT: 35
± 9
Significant group × time interaction revealed reduced
body mass and adiposity in FAST, without changing
lean mass, whereas CNT subjects remained
unchanged. Although RF induces diurnal metabolic
adjustments (morning v. evening), no carryover effect
was observed throughout Ramadan fasting despite
the extended daily fasting period and changes in body
composition.
Nutrients 2019, 11, 1192 4 of 15
[30] 2009
Healthy fasting
adults, n = 46; 24
female and 22 male.
Female and
male; 24 ± 3
Total energy intake was higher during Ramadan (13
and 11 MJ/day) than before and after Ramadan (11
and 9 MJ/day) in men and women, respectively.
[31] 2011 173 families fasting
Ramadan
Female and
male; age
unspecified
59.5% reported weight gain post-Ramadan; 40%
attributed food types, 31.2% attributed to relative lack
of physical exercise and 14.5% referred that to increase
in food consumption. 65.2% of those with increased
expenditure reported weight gain.
[32] 2007
Healthy fasting
adults at one-week
pre-Ramadan (T1),
first week (T2), end of
second week (T3),
and end of last week
(T4) of Ramadan; n =
57
Female; 22
± 4
Body weight and BMI decreased significantly during
Ramadan fasting. The mean physical activity level was
not significantly different. The overall activity patterns
remained similar; 1.54 pre-and 1.51 during Ramadan
2.1. Short-Term Fasting
Metabolically, fasting can be divided into three distinct key stages: Stage 1: a post-absorptive
phase ~6–24 hours after beginning fasting where the central nervous system (CNS) and many other
issues preferentially use glucose produced from glycogen breakdown. Lipolysis and ketogenesis
and gluconeogenesis increase, but the latter to a lower extent. Glycogenolysis decreases. Stage 2: the
gluconeogenic phase occurs ~1–10 days after beginning fasting. Here, protein catabolism is used to
feed glucose to the CNS while other tissues feed on ketones and fat. Lipolysis and ketogenesis
increase and then plateau, gluconeogenesis on the other hand begins to decrease and no
glycogenolysis occurs. Stage 3: is a protein conservation phase that occurs when fasting extends
beyond 10 days. Protein catabolism is decreased to a minimum, fatty acids are used ubiquitously
and ketones are utilized as fuel in the CNS. Lipolysis and ketogenesis plateaus while
gluconeogenesis decreases and then plateaus but to a much lower extent when compared to
ketogenesis [33,34].
2.2. Prolonged Fasting-Some Historic Examples
Early studies in 1915 by Francis Benedict looking into chemical and physiological alterations in
a lean man fasting thirty-one days demonstrated significant declines in body weight (12.4 kg with a
rate of 0.84 kg/day at Day 1 declining to 0.32 kg/day by Day 31), (Figure 1). Levels of various
biological markers such as body temperature and blood pressure were maintained [35,36].
In 1916, Spriggs reported various cases of fasting used as a method to treat diabetes whereby
fasting was ‘continued in bed until the urine has been sugar-free for twenty-four hours, unless there
is some definite contraindication, such as nausea, vomiting, insomnia, or faintness’ [37]. Early
studies also indicated a progressive decrease in daily urinary nitrogen excretion suggestive of an
increase in conservation of body protein [38] and that urine output gradually decreased throughout
the fasting period [39].
In 2006, a study on prolonged absolute fast (44-days) on a healthy non-obese man shed light on
changes in various metabolic parameters [40]. The TEE was not measured, but was estimated to be
1638–2155 kcal/day of which 13.0–17.1% was from protein oxidation. Total weight loss was 24.5 kg
and body mass decreased by 25.5%; a quarter to a third was fat mass and the remainder to fat-free
mass which was predominantly muscle and approximately 20% was total body protein.
More recently, in 2015, Müller and colleagues investigated effects of caloric restriction (CR) and
weight loss on 32 subjects aged between 20–37 years old in a controlled environment. Patterns of
habitual food intake, resting energy expenditure and physical activity were assessed. The 10 week
(week) dietary intervention period duration included 1 week of overfeeding (at +50% of daily energy
requirements; 4059 ± 52 kcal/day) followed by 3 weeks of CR (at 50% of energy requirements; 1353 ±
154 kcal/day) and a subsequent 2 weeks of re-feeding (at +50% of energy requirements; 4059 ± 452
kcal/day). Protein intake was 97 ± 11 g/day (baseline); 146 ± 17 g/day (overfeeding), 49 ± 6 g/day
(CR), and 146 ± 17 g/day (re-feeding), respectively. The study reports a +1.8 kg weight gain
Nutrients 2019, 11, 1192 5 of 15
(overfeeding), 6.0 kg (CR), and +3.5 kg (re-feeding). CR reduced fat mass and fat-free mass from
skeletal muscle (5%), liver (13%), and kidneys (8%) by a total of 114 and 159 g/day, respectively.
CR also led to reductions in resting energy expenditure (266 kcal/d) and respiratory quotient
(15%). The study concluded that during early weight loss, adaptive thermogenesis is associated
with a fall in insulin secretion and body fluid balance [41].
(a)
(b)
Figure 1. Time-dependent Changes in Weight during Prolonged Fasting (31 Days). Adapted from:
Francis Gano Benedict: A study of Prolonged Fasting. (a), Daily Net Weight Loss: calculation of daily
weight reduction in 31 days (D) of fasting. Initial weight was 59.86 kg at D1, final weight was 47.47
kg at D31, total weight loss 12.4kg. R2 = 9798 indicated a linear relationship between time and net
weight loss. (b) Changes in Rate of Daily Weight Loss: relative to starting rate of weight loss, rate of
weight loss per day indicates various changes whereby a steep rate of weight loss we observed in the
first five days of fasting (D1–5; Maximum Rate 0.67), followed by a slower rate of weight loss in the
following 10 days (D5–15; Maximum Rate 0.64), which decreased further in the next 10 days (D15–25;
Maximum Rate 0.47) before reaching a plateau in the last five days of the fasting month (D25–30;
Maximum Rate 0.42).
3. The Ramadan Fast: A Shift from Normal Eating Patterns
A typical eating pattern in most cultures includes three main meals, often accompanied by
snacks in between (Figure 2). Alterations in this ‘normal’ pattern can have important implications to
energy balance. Some of the more common fasting regimens include intermittent fasting (IF),
periodic fasting (PF) and time restricted fasting (TRF) [8].
y = -0.3724x + 58.582
= 0.9798
44.00
46.00
48.00
50.00
52.00
54.00
56.00
58.00
60.00
62.00
1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031
Weight (Kg)
Day of Fast (Day)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 2 3 4 5 6 7 8 910111213141516171819202122232425262728293031
Relative Rate of Weight Change
Day of Fast (Day)
Max = 0.67
Range (0-0.67)
Max = 0.64
Range (0.64-0.47)
Max = 0.47
Range (0.47-0.42)
Max = 0.42
Range (0.42-0.40)
Nutrients 2019, 11, 1192 6 of 15
(a)
(b)
Figure 2. Changes in Feeding Patterns and Energy Intake during Various Fasting Periods. The five
feeding and fasting patterns are: (I) normal feeding, (II), calorie restriction, (III) intermittent fasting
(e.g., 5:2), (IV) Ramadan fast and (V) prolonged fasting and starvation. (a) Hourly Differences in
Feeding Patterns between Various Fasting Models: hourly timings of feeding and energy intake
(meals) are indicated per day in relation to fasting periods (arrows) and reflected in glycaemic
control (traces). (b), Daily and Weekly Differences in Feeding Patterns Between Various Fasting
Models: daily and weekly feeding patterns are mapped against calorie intake which can be regular
such as in in normal feeding (I), indicated by single colour arrows or a combination of low, normal or
high calorie intake as in intermittent fasting (III), indicated by mixed colour arrows. Ramadan fast
(IV) is unique as it combined low and high calorie intake as indicated by the two single colour
arrows. The first week is broken down into seven individual days. Weekly indications follow
thereafter.
Nutrients 2019, 11, 1192 7 of 15
Ramadan fasting and Ramadan-type fasting are somewhat different from other forms of fasting
mentioned above. Ramadan, the ninth month in the Islamic Calendar, requires Muslims to fast daily
from dawn to dusk and the criteria are clearly defined in the Holy Quran [2]. No food or drink is
allowed after suhoor until iftar. The fast is traditionally broken with something sweet such as dates.
This is followed by the main meal which tends to be heavy and carbohydrate-rich. Between iftar and
suhoor, food can be taken without any restriction. Ramadan is a lunar month and as such lasts 29-30
days. The fast is a religious obligation for all adult Muslims. Exempt groups include the sick and also
women during their menstrual period. Many people who are religiously exempt opt to fast, often for
social and cultural reasons.
In addition to Ramadan fasting, many Muslims practice the same dawn-to-sunset type of fast
on other days of the year and this may include Mondays and Thursdays. Fasting some days may
have some physiological differences from fasting an entire month as some physiological adaptations
which may happen later during Ramadan may not occur in the short term.
4. The Ramadan Diet
Management of a healthy balanced diet is necessary not only for the maintenance of a healthy
weight, but for the maintenance of the overall nutritional health of individuals too. Energy intake
plays a central role [42]. Nonetheless, multiple factors influencing energy intake such as cultural and
lifestyle differences, make it difficult to maintain healthy balanced diet long-term. During
non-fasting periods, recent statistics indicate that average daily adult energy intake is: (1) 2250
kcal/day (female 2,000 and male 2,500 kcal/day) in the UK [43], (2) 2300 kcal/day (female 2,000 and
male 2,600 kcal/day) in the USA [44] and 2255 kcal/day (female 2,010 and male 2,600 kcal/day) in
Australia [45]. Collectively, an average adult consumes ~2268 kcal/day (female 2,003 and male 2,533
kcal/day) (Figure 3A) with an additional margin for genetic (e.g., predisposition to
overweight/obesity) and environmental influences (e.g., daily activity and feeding habits).
Ramadan nutrition planning (RNP) is encouraged as per DaR guidelines, which take into
consideration variations in cultural food choice and calorie consumption (range of 1200kcal/day for
weight reduction for females to maximum of 2000 kcal/day weight maintenance for males) [46]. Due
to the inevitable changes in feeding patterns and associated physiological shifts in circadian
rhythms, hormone levels fluctuations and overall daily lifestyle, Ramadan meal planning becomes
an essential component for healthy Ramadan fasting. This is of particular importance for patients
with chronic conditions, such as diabetes. A ‘Ramadan Plate’ is recommended to contain a balanced
selection of carbohydrates (40–50% of total daily calorie intake (TDCI) of low glycaemic index and
high-fibre containing foods), protein (20–30% of TDCI of non-red meat sources and legumes) and
reduced fat intake (35% of TDCI of mostly mono- and poly-saturated fatty acids). Suhoor, the
pre-dawn meal, is recommended to constitute 30–40% energy intake for the day, iftar 40–50% and
snacks 10–20% as necessary.
In theory, in terms of energy intake, skipping one main meal in a 24-hour period should be
associated with a major reduction in food content and energy intake. This is the principle in the
intermittent 5:2 fasting diet where fasting can be up to 18 hours (Figure 2A (III) and 2B (III)).
Therefore, during Ramadan, in addition to eating healthily, this reduction in energy intake could
lead to weight loss but in practice this does not occur in most cultures (Figure 3B). Many studies
indicate a great variability in Ramadan diets [30,47] in different cultures, age groups, geographical
locations and duration of fasting hours as well as the impact of physiological and pathological
conditions (e.g., diabetes) and associated with modest reduction of energy intake in most but not all
groups studied.
El Ati and colleagues investigated a group of 16 healthy female volunteers fasting during
Ramadan and reported 84% of total daily energy intake was taken at the evening meal, and the
remaining 16% was taken between 8 p.m and midnight. This is in contrast to periods before
Ramadan where breakfast, lunch and dinner constituted 9.4, 41.6 and 21.8% of total daily energy
intake. Although the findings of this small study cannot be generalized to the larger population of
Nutrients 2019, 11, 1192 8 of 15
fasting Muslims, the observation of a disproportionately large meal at iftar time is a common finding
[31,48]; often reflected in feeding patterns (Figure 2) and in glycaemic profiles.
(a)
(b)
Figure 3. Energy intake (EI) recommendations and resultant weight changes in Ramadan and
non-Ramadan periods. Energy intake recommended guidelines for female and male adults. (a)
indicates values for the (1) UK 2250 kcal/day (female 2,000 and male 2,500 kcal/day), (2) the USA 2300
kcal/day (female 2,000 and male 2,600 kcal/day) and (3) for Australia 2225 kcal/day (female 2,010 and
male 2,600 kcal/day). Collectively, an average adult consumes ~2270 kcal/day (female 2,003 and male
2,533 kcal/day). (b), Energy intake recommendations during Ramadan in comparison to standard
and low calorie diets. in order of left to right: based on the calculated average of 2270 kcal/day as a
standard adult EI (Figure 3A), a healthy Ramadan diet matched calorie intake is achievable. In
reality, a higher EI is experienced in Ramadan (~3000 calories). However, weight maintenance (at
1800 kcals/day) is achievable during Ramadan as suggested by Diabetes and Ramadan (DaR)
Alliance Ramadan Nutrition Plans (RNP) recommendations. This holds true for weight loss at the
1500 and 1200 kcals/day calorie EI for both non-Ramadan and Ramadan periods.
Nutrients 2019, 11, 1192 9 of 15
5. Weight and Body Composition Changes during Ramadan Fasting
There seems to be much inter-individual variability in weight trends with Ramadan fasting and
as with other modalities of weight change; one would expect these to be determined by individual,
cultural and social factors as well as genetic, epigenetic and other factors such as gut microbiome.
Several small studies (with participants between 16–81 years old in most) have examined the
effect(s) of Ramadan on body weight and reported a modest weight loss of 1–2 kg by the end of
Ramadan, with some other studies reporting weight gain [18,19]. A meta-analysis of the older
studies (by Kul et al., 2014) showed a small weight loss of around 0.7 kg in fasting men, but no
significant change in fasting women [18]. The largest study of 202 participants (Hajek et al, 2012)
recruited at mosques in East London showed a net weight loss of around 0.8 kg by the end of
Ramadan [49]. As in some other studies that had post-Ramadan weight recorded, this study showed
that all the lost weight was regained 4–5 weeks after Ramadan [18]. In terms of satiety and hunger,
the levels remained the same for males during Ramadan while for females more hunger was
experienced earlier in the month and then decreased as the Ramadan month progressed [30,50].
In a more recent excellent meta-analysis, Fernando and colleagues showed that the mean
weight loss with Ramadan fasting was 1.34 kg and that most of the weight was regained a few weeks
post-Ramadan [51]. It has also been shown that weight loss is greater among Asian populations
compared with Africans and Europeans [19] and that there does not appear to be any gender
difference in the absolute magnitude of weight loss with Ramadan fasting.
6. Energy Expenditure during Ramadan Fasting
6.1. Resting Metabolic Rate (RMR) During Ramadan Fasting
RMR is known to decrease with prolonged fasting and this may be a counter-regulatory way to
decrease energy loss (Benedict, 1915; Forbes, 1987; Garrow, 1978; Woo et al., 1985) [26]. Studies into
RMR changes in Ramadan are however few in number. A study by El Ati and colleagues (1995) is
the earliest reported [28]. Different aspects of EE in the context of the Ramadan fast in 16 female
participants were explored. RMR at four different time points around Ramadan (before Ramadan,
the first week of Ramadan, the last week of Ramadan, and the month after Ramadan) were
investigated along with daily EE trends. The study reported a reduction in RMR during Ramadan
and metabolic rate patterns were found to be different between Ramadan and non-Ramadan days;
lower during the fasting day versus night, with a rise around iftar, but no significant change overall.
Total daily energy intake, body weight, fat mass and fat free mass remained unchanged. Similarly, a
study by Bahammam and colleagues found a reduction in EE and metabolic equivalents (METs)
measured by accelerometry during Ramadan fasting [14]. In our own study of 45 male and female
subjects we found no overall difference in RMR between Ramadan and non-Ramadan periods
(mean ± SD: 1365 ± 230 compared with 1363 ± 274 kcal/day for Ramadan and post-Ramadan
respectively, p = 0.713, n = 29). However, multiple linear regressions and controlling for the effects of
age, sex, and body weight, RMR was higher in the first week of Ramadan and showed a significant
downward trend in subsequent weeks [24] potentially due to metabolic adaptation medicated both
centrally and locally (e.g., via gut hormones). Thorough investigations, particularly in the context of
Ramadan, need to be conducted to more accurately and precisely assess the contribution of these
individual factors in fasting-related energy regulation.
6.2. Activity Energy Expenditure (AEE) During Ramadan Fasting
As well as changes in meal times and content, Ramadan period is associated with major
changes in activity patterns throughout the fasting day. Much of the daily activity and AEE tends to
occur nocturnally after iftar [52] with inter-individual variability reported in various other studies
[32,52,53]. A recent study by our group (Lessan et al., 2018) investigated daily activity patterns using
accelerometers an overall reduction in daily activity energy expenditure [24]. Differences in daily
activity patterns between Ramadan and non-Ramadan periods were observed (Figure 4). Activity in
Nutrients 2019, 11, 1192 10 of 15
the morning (1974 ± 583 compared with 3606 ± 715, p = 0.001) and afternoon (3193 ± 783 compared
with 4164 ± 670, p = 0.002) were significantly lower during Ramadan compared with post-Ramadan.
Nocturnal activity was higher during Ramadan (1261 ± 629 compared with 416 ± 279, p = 0.001). No
significant difference in evening activity levels between during and post-Ramadan periods was seen
however the study found a reduction in activity during fasting hours and a rise after iftar.
Furthermore, major change in sleeping patterns and times was reported.
6.3. Thermic Effect Of Food (TEF) During Ramadan Fasting
There have been no studies specifically investigating TEF in the context of Ramadan fasting and
it is difficult to speculate how TEF would change with the Ramadan fast. However, there are a
number of considerations in speculating what changes to TEF might be expected with the Ramadan
fast. Firstly, TEF is related to serum insulin and insulin resistance. Insulin resistance and plasma
insulin level are known to be higher during the Ramadan fast, especially in the evening and around
iftar period. This may lead to a reduction in TEF. Secondly, dietary fat has a lower thermic effect
than protein. Several studies of diet during Ramadan have indeed, reported a higher fat content; this
can also cause a reduction in TEF during Ramadan. Finally, a major meal is skipped during
Ramadan, and although this can in part be compensated by over-snacking at nights, a net reduction
in TEF may be expected. Well-conducted studies of TEF during Ramadan can provide a better
insight into energy dynamics during Ramadan and help with weight management around the
Ramadan period.
6.4. Fuel Utilization During Ramadan Fasting
Few studies have investigated fuel utilization in the context of the Ramadan fast. Using indirect
calorimetry, El Ati has shown that during Ramadan fat oxidation increases through the fasting day.
Carbohydrate oxidation decreases gradually from morning to iftar time. The differences in fuel
oxidation at different time points in Ramadan and non-Ramadan days were significant [51].
AlSubheen and colleagues have also shown that carbohydrate oxidation drops and lipid oxidation
gradually increases through the Ramadan fasting day [29].
6.5. Total Energy Expenditure (TEE) During Ramadan Fasting
El Ati and colleagues reported measurements of energy expenditure by indirect calorimetry at
several time points through Ramadan and non-Ramadan days reportedly in a metabolic chamber.
No total energy expenditure values were however reported. Substrate oxidation and biochemical
assays were also carried out over the four-day test period between 8 a.m and 11 p.m at three hourly
intervals. The study reports that resting energy expenditure measured at 8 a.m remained unchanged
during and after Ramadan, compared to pre- Ramadan durations. However, the EE throughout the
circadian cycle was dramatically affected during Ramadan fasting periods whereby, and unlike the
nightly energy expenditure values, a significant decrease in energy expenditure was observed from
11 a.m to 5 p.m hours during Ramadan fasting periods [13].
Our study in healthy non-obese volunteers investigated changes in RMR and TEE in free-living
conditions. The study of TEE utilizing doubly-labelled water and accelerometer aided techniques by
our group reported no differences in TEE between Ramadan and Post-Ramadan periods (mean ± SD:
2224 ± 434 compared with 2121 ± 719 kcal/day for Ramadan and Post-Ramadan, p = 0.7695, n = 10)
(Figure 4). TEE did not differ significantly between Ramadan and Post-Ramadan [24]. The insulin
resistance observed [24] was a result of the compounding factors of reduction in circulating leptin, a
gradual shift from carbohydrate to lipid as dominant fuel as the fasting day progresses and the
variable weight change determined by individual, social and cultural factors, rather than
physiological changes.
Nutrients 2019, 11, 1192 11 of 15
(a)
(b)
(c)
Figure 4. Energy expenditure and physical activity pre-, during and post-Ramadan. (a) Box plot of
daily total number of steps during and post-Ramadan. The effect of Ramadan fasting on activity in 11
participants. (b) Box plot of total number of steps at different periods within one day (per night,
morning, afternoon, and evening) during and post-Ramadan in 11 participants. Comparisons made
with the Wilcoxon signed-rank test. Total mean ± SD number of steps per day (9950 ± 1152 compared
with 11,353 ± 2053, p = 0.001), activity in the morning (1974 ± 583 compared with 3606 ± 715, p = 0.001)
and afternoon (3193 ± 783 compared with 4164 ± 670, p = 0.002) were significantly lower during
Ramadan compared with post-Ramadan. Nocturnal activity was higher during Ramadan (1261 ± 629
compared with 416 ± 279, p = 0.001). No significant difference in evening activity levels between
during and post-Ramadan periods was observed. (c) TEE and RMR during and post-Ramadan: the
correlation between TEE and weight during and post-Ramadan in 10 participants. No significant
difference between Ramadan and post-Ramadan regression lines (ANCOVA; t = 0.35, p = 0.727); the
main factor influencing TEE was body weight (t = 2.72, p = 0.015).
Nutrients 2019, 11, 1192 12 of 15
7. Discussion and Concluding Remarks
Calorie restriction and different forms of fasting have been shown to have major physiological
effects; from health benefits to longevity [6,54]. Ramadan fasting has also been shown to have
beneficial effects including positive changes in body composition with reported reduction in body
fat as well as weight loss which is a common although not universal consequence [50]. Similar to
calorie-restricting diets targeting calorie reduction at ~500–800 kcal/day [55], skipping a meal during
fasting, such as in the context of Ramadan, can theoretically lead to weight loss. However, dietary
changes during Ramadan vary and often include an increase in carbohydrate intake [56,57].
Weight loss strategies including many dietary interventions are often unsuccessful in the
medium and the long term. One explanation for this is the phenomenon of adaptive thermogenesis.
This occurs by promoting optimization of energy reserves while preserving protein pools via
reduction in basal metabolism, decrease in secretion of anabolic factors (e.g., insulin) and increase in
catabolic hormones (e.g., adrenaline and glucagon) [3]. Along with protein loss, weight loss also
occurs; initially at a higher rate (~1kg/day) which then decreases (~0.7 kg/day by 24 hrs, 0.5 kg/day
by day 6 and 0.3 kg/day from day 21 onwards) [33]. Importantly, the few small studies of energy
expenditure in the context of Ramadan fast have found no evidence of a metabolic adaptation [24].
This finding needs to be investigated in larger studies and if confirmed, may have important
implications on Ramadan and IF as potential weight loss strategies. Admittedly, overcompensation
with an increase in energy intake at the evening meal is common practice in observers of the
Ramadan fast [31]. Although the increased appetite at the end of the fasting day [49] is the main
drive for this phenomenon, this is in many ways voluntary. With appropriate education and a shift
in food choices it may be possible to limit this increase in intake of energy dense food and make the
prospect of weight loss with the Ramadan fast more realistic.
Aside from weight changes, Ramadan fasting induces a plethora of physiological and metabolic
alterations. The impact of Ramadan on sleep alone includes decreased total sleep time, delayed
sleep, decreased sleep period time (decreased REM sleep duration, decreased proportion of REM
sleep) and increased proportion of non-REM sleep [13]; also reported with high inter-individual
variation.
An important issue on interpretation of Ramadan studies is the potential hypohydration that
would be expected towards the end of the Ramadan fasting day. A study investigating the effects of
prolonged fasting and fluid deprivation reported a loss of body weight of around 1.5 kg in
individuals fasting between 10 pm and 4 pm the next day; the weight loss was presumed to be due
to loss of body water [39]. Fluid homeostasis during Ramadan fast has been investigated in several
studies and has been reviewed elsewhere [58]. Water turnover has been shown to increase during
Ramadan fast with concomitant increases in indicators of body hydration including haematocrit,
serum urea and creatinine and urine osmolality. However, total body water appears to be conserved
and aside from potentially contributing to weight loss that might be observed in Ramadan, no
detrimental effects on health have been directly attributed to negative water balance and
hypohydration at the levels experienced during Ramadan [58]. Furthermore, hypohydration has
been shown to have no significant effect on RMR and blood glucose in healthy subjects [59].
Studies of Ramadan fasting in general need to be interpreted carefully and with consideration
for certain factors such as the timing of previous meal, methodological differences and also
hydration status. An important and relevant factor in studies of Ramadan fasting is the duration of
the fast, and hence geographical location; the impact tends to be most marked in countries at higher
altitudes and with more daylight hours [60]. Fasting hours also include the seasonal changes
whereby fasting Ramadan during winter months for instance would have physiologically different
effects when compared to fasting Ramadan during summer months. Although the literature
specifically pertaining to energy expenditure changes during Ramadan is steadily mounting, it is
currently small in number. Therefore, future studies need to address these variables to tackle the
inter-variability issues that continually arises in the current literature.
In conclusion, although the metabolic consequences of Ramadan fast are complex, there is
potential for using this month as a weight reduction model provided the fasting is carried out
Nutrients 2019, 11, 1192 13 of 15
mindfully; balancing food type, quantity and levels of physical activity. Pre-Ramadan planning
(nutrition plans, medication and health checks) is necessary; more so for individuals with chronic
conditions such as diabetes who need specialist advice should Ramadan fast be deemed suitable in
the first place. The long-term effects are thus of interest and studies are necessary for elucidation.
Author Contributions: The authors have contributed equally to the writing and editing of the manuscript.
Funding: This research received no external funding.
Acknowledgments: This work has been supported by Imperial College London Diabetes Centre (ICLDC).
Conflicts of Interest: The authors declare no conflict of interest.
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... Meanwhile, a previous clinical trial showed that the serum total cholesterol, triglycerides, and HDL-cholesterol in Muslims were decreased significantly by RIF [72]. Interestingly and controversially, some studies observed weight gain [73], which might have resulted from the increased energy intake during the evening meal and changes in circadian rhythms. Previous evidence also suggested that RIF potentially increases cardiometabolic risk, which was proposed to be caused by the change in circadian rhythm with the mealtimes. ...
... Proper appetite is crucial to the health of living organisms [73]. The change, loss, or gain of appetite may be a concern that has to be dealt with during or after IF intervention. ...
Article
Full-text available
Obesity has been an escalating worldwide health problem for decades, and it is likely a risk factor of prediabetes and diabetes. Correlated with obesity, the number of diabetic patients is also remarkable. A modest weight loss (5–10%) is critical to alleviate the risk of any other metabolic disease. Reduced energy intake has been an essential factor for weight loss reduction. As a new behavior intervention to lose weight, intermittent fasting (IF) attracts considerable attention and has become a popular strategy among young people. IF is a diet pattern that cycles between periods of fasting and eating on a regular schedule, involving various types, mainly Intermittent Energy Restriction and Time-Restricted Fasting. Accumulating evidence shows that short-term IF has a greatly positive effect in animal studies and contributes favorable benefits in human trials as well. Nevertheless, as an emerging, diverse, and relatively premature behavior intervention, there are still limited studies considering patients with obesity and type 2 diabetes mellitus. It is also a controversial intervention for the treatment of metabolic disease and cancer. The risks and challenges appear consequently. Additionally, whether intermittent fasting can be applied to long-term clinical treatment, and whether it has side effects during the long-term period or not, demands more large-scale and long-term experiments.
... Fasting is defined as abstaining from food and drink from predawn to sunset. This requires a major shift from natural eating patterns to unique night eating [1,2]. Also, during Ramadan fasting, the amount, type, and quality of food consumed changes. ...
Article
Background and aims To quantify the bibliometric parameters of Ramadan fasting literature from 2010 to 2021. Materials and methods Scopus was searched for all articles related to Ramadan fasting or Islamic fasting from the beginning of 2010 to the end of 2021. Only original articles and reviews were included and their bibliometric and scientometric parameters were determined using Excel, Graph Pad Prism, VOSviewer, and Sci2 tool software. Results Finally 1276 articles, including 1109 original articles and 167 reviews, were included. These articles had 14263 citations and an H-index of 48. Based on the number of publications, top institute, top journal, top country, and top authors were University of Sfax (n = 48 articles), Diabetes Research and Clinical Practice (n = 69), the United States (n = 144), and Chtourou H & Hassanein M (n = 38), respectively. Also, Diabetes Research and Clinical Practice had a strong bibliographic coupling with other journals. The recent bursting words were adrenal insufficiency and COVID-19. The most co-occurred topics were the effect of Ramadan fasting on diabetic patients, pregnant women, and glycemic state and body composition of diabetic patients. Conclusion This study provided a comprehensive bibliometric overview of Ramadan fasting literature from 2010 to 2021. The temporal change in the number of publications and other analyses on the literature of 2019, 2020 and 2021 showed that substantial increasing publications with new emerging subjects had become of interest to many researchers during the last three years.
... Observers refrain from eating food, drinking liquids, and other physical needs such as smoking and sexual intercourse Jahromi et al., 2014). Ramadan fasting (RF) as intermittent fasting is mandatory for all healthy adult Muslims (Akbari et al., 2022;Lessan & Ali, 2019). Several studies have been conducted over the last decade to investigate the impact of RF on physiological performance (Maughan et al., 2010;Zerguini et al., 2007). ...
Article
This study aimed to investigate the effect of a walking football (WF) program during Ramadan fasting (RF) on heart rate variability (HRV) indices, body composition, and physical fitness in middle-aged males. Thirty-one healthy sedentary men were randomized to WF ( n = 18) and control ( n = 13) groups. Both groups participated in RF. The WF group were involved in a training program (small-sided games) of three sessions a week during RF. The time and frequency domains of HRV, body composition, handgrip, lumbar strength, Modified Agility Test (MAT), and 6-minute walk test (6MWT) were measured before Ramadan (BR), during Ramadan (DR), and after Ramadan (AR). We reported that RF has significantly altered some parameters of HRV DR; the mean HR decreased while the mean RR, LF, and HF increased. WF had a significant effect on HRV and mean HR DR compared with BR and AR decreased while mean RR, HF and LF increased. DR, body mass decreased in both groups, while body mass index (BMI) decreased and lean mass increased only in WF group. Lower body mass and BMI levels were reported AR only in WF group. Physical capacity improved AR, compared with BR, only in the WF group with longer distance in 6MWT, shorter time(s) in MAT, and higher lumbar strength levels. We conclude that RF increases parasympathetic system activity. WF practice during RF is safe and might improve body composition, physical fitness, autonomic cardiac function, and physical fitness in middle-aged males.
... Fasting is defined as abstaining from food and drink from predawn to sunset. This requires a major shift from natural eating patterns to unique night eating [1,2]. Also, during Ramadan fasting, the amount, type, and quality of food consumed changes. ...
Article
Background and aims To quantify the bibliometric parameters of Ramadan fasting literature from 2010 to 2021. Materials and methods Scopus was searched for all articles related to Ramadan fasting or Islamic fasting from the beginning of 2010 to the end of 2021. Only original articles and reviews were included and their bibliometric and scientometric parameters were determined using Excel, Graph Pad Prism, VOSviewer, and Sci2 tool software. Results Finally 1276 articles, including 1109 original articles and 167 reviews, were included. These articles had 14263 citations and an H-index of 48. Based on the number of publications, top institute, top journal, top country, and top authors were University of Sfax (n = 48 articles), Diabetes Research and Clinical Practice (n = 69), the United States (n = 144), and Chtourou H & Hassanein M (n = 38), respectively. Also, Diabetes Research and Clinical Practice had a strong bibliographic coupling with other journals. The recent bursting words were adrenal insufficiency and COVID-19. The most co-occurred topics were the effect of Ramadan fasting on diabetic patients, pregnant women, and glycemic state and body composition of diabetic patients. Conclusion This study provided a comprehensive bibliometric overview of Ramadan fasting literature from 2010 to 2021. The temporal change in the number of publications and other analyses on the literature of 2019, 2020 and 2021 showed that substantial increasing publications with new emerging subjects had become of interest to many researchers during the last three years.
... Besides, they combine plentiful of health-benefiting antioxidants, vitamins, minerals, and plant sterols (72). Beans are rich source of dietary fibers (66%) which act as a bulk laxative, protect colonic mucosa by decreasing its exposure time to toxic substances, adsorb carcinogens helping its excretion, and reduce blood cholesterol levels by decreasing re-absorption of cholesterol binding bile acids in the colon (73). ...
... This type of inflammation is associated with poor physical activity, being overweight, tobacco use and poor eating habits. Other benefits of decreased caloric intake have been shown, such as an increase in life expectancy, delayed onset of aging-related diseases, avoiding or preventing age-related brain deficits, increasing visual cortex plasticity, and improving cognitive function [12][13][14][15][16].One of the diets based on caloric restriction is intermittent fasting, which is a dietary regimen consisting of periods in which caloric intake is reduced and others in which a normal diet is followed [13]. The objective of this regimen is to induce a reduction in net energy intake that makes it fall below energy expenditure, thus creating a negative energy balance state that induces weight loss, among other results [17]. ...
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Evidence shows that the use of food strategies can impact health, but a clear consensus about how the effects of different food strategies impact improvement in the athlete's performance and health remain unclear. This study evaluated how food strategies, specifically intermittent fasting and a ketogenic diet affect health and performance in healthy athletes. Study selection for this review was based on clinical trial studies analyzing changes in performance and health in athletes. The Pubmed, Web of Science, PEDro, Dialnet, Scopus, CINAHL, ProQuest, Medline and Cochrane databases were searched. The Physiotherapy Evidence Database (PEDro) scale, PEDro Internal Validity Scale (IVS) and Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a variety of fields (QUALSYT) checklists were used to evaluate the risk of bias of the included studies. Articles were selected based on criteria concerning the effectiveness of nutritional strategies on athletes' performance; articles should be randomized clinical trials (RCTs) or uncontrolled clinical trials; they should be human studies and they should have been published less than 7 years ago. A total of 15 articles were evaluated, 8 randomised clinical trials and 7 non-randomized clinical studies, with 411 participants who satisfied our inclusion criteria and were included in this review. The results of the study showed intermittent fasting and time-restricted feeding as strategies that produce health benefits. On the other hand, the ketogenic diet did not reach an appropriate consensus. The articles presented a medium level of methodological quality in the PEDro scale, low quality in IVS scale and high quality in QUALSYT scale. Despite the lack of studies analyzing changes in the performance and health of athletes after the use of different nutritional strategies, intermittent fasting and time-restricted feeding should be considered since they seem to be effective, and further studies are necessary.
... Although the sick are religiously exempt from the practice of RF, many choose to fast for cultural, social, personal as well as religious reasons. With the changes in meal patterns and sleeping times, physiological changes occur with RF (1)(2)(3). The long gap between main meals also dictates changes in medication timing (4). ...
Article
Background Ramadan fasting (RF) is associated with major changes in meal times. This can affect thyroxine absorption and thyroid function (TF) in patients with hypothyroidism. We aimed to examine the short and long-term impact of RF on TF in patients with primary hypothyroidism on levothyroxine. Methods Thyroid function tests in patients with primary hypothyroidism attending an endocrine centre in the UAE were retrospectively analysed. The impact of RF on TF, namely serum thyrotropin TSH, free thyroxine FT4 and free triiodothyronine FT3, was investigated in 481 patients within 3 months before Ramadan (BR), 1-2 weeks (PR1), and 3-6 months (PR2) post-Ramadan. Controlled TF was defined as TSH between 0.45-4.5 uIU/ml. Inadequate control was defined as TSH > 4.5 uIU/ml. Loss of control was defined as having controlled TF at BR and inadequate control at PR1. Multivariate regression analyses were used to assess the association of baseline TSH, baseline levothyroxine dose, and medication use with loss of thyroid control in Ramadan. Results TSH increased significantly from a median of 2.0 (0.8-3.7) uIU/ml at BR to 2.9 (1.4-5.6) uIU/ml at PR1 (P < 0.001). This was accompanied by a fall in FT4 and FT3 at PR1 (P<0.001). 25.5% of patients with previously controlled TF at BR had deterioration in TF at PR1. 61% of patients with previously uncontrolled TF at BR remained uncontrolled at PR1. Baseline TSH was significantly associated with loss of thyroid control in Ramadan with an odds ratio (95% CI) of 1.5 (1.17,1.92) (P < 0.001), whereas other variables, including medications known to affect levothyroxine absorption were not associated with loss of control. TSH, FT4, and FT3 levels returned to normal at PR2. Conclusions RF can negatively affect TF of patients on levothyroxine replacement. Although this effect is modest and transitory in most patients, a significant minority exhibit more pronounced, and clinically relevant changes. The latter include those with higher TSH before Ramadan, and a smaller group whose thyroid disease appears to be particularly affected by the meal time and lifestyle changes of Ramadan.
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COVID-19 restrictions are associated with poor physical-activity (PA). Less is known about the relationship between the combination of these restrictions with Ramadan intermittent fasting (RIF), PA, mental health, and sleep-quality. The present study aimed to evaluate whether COVID-19 restrictions and RIF during the fourth wave of the COVID-19 pandemic in Iran are associated with poor PA, anxiety, well-being, and sleep-quality outcomes. A total of 510 individuals participated in an online questionnaire that was disseminated to adults (≥18 years) residing in Iran from 13 May 2021 to 16 May 2021 (~3 days), just after the end of Ramadan 2021. PA behavior (Godin-Shephard Leisure-Time Exercise Questionnaire), anxiety (General Anxiety Disorder-7), well-being (Mental Health Continuum-Short Form), and sleep-quality (Pittsburgh Sleep Quality Index). Of 510 individuals included in the study (331 female (64.9%); mean ± SD, 31 ± 12 years), 172 (33.7%) reported less PA during the Ramadan 2021. PA was associated with better well-being and sleep-quality outcomes. Regardless of PA, participants who fasted for all of Ramadan had less anxiety and better well-being outcomes than those who fasted part of Ramadan or did not fast at all. However, the fasting part of Ramadan decreased the sleep-quality of active participants. The Ramadan 2021 was associated with poor PA, well-being, and sleep-quality of Iranians. However, PA was associated with better well-being and sleep-quality outcomes, and those who fasted all Ramadan had better anxiety and well-being outcomes. Therefore, PA during Ramadan might be an essential and scalable mental health resilience builder during COVID-19 restrictions which should be encouraged.
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Background: Ramadan involves one month of fasting from sunrise to sunset. In this meta-analysis, we aimed to determine the effect of Ramadan fasting on weight and body composition. Methods: In May 2018, we searched six databases for publications that measured weight and body composition before and after Ramadan, and that did not attempt to influence physical activity or diet. Results: Data were collected from 70 publications (90 comparison groups, 2947 participants). There was a significant positive correlation between starting body mass index and weight lost during the fasting period. Consistently, there was a significant reduction in fat percentage between pre-Ramadan and post-Ramadan in people with overweight or obesity (−1.46 (95% confidence interval: −2.57 to −0.35) %, p = 0.010), but not in those of normal weight (−0.41 (−1.45 to 0.63) %, p = 0.436). Loss of fat-free mass was also significant between pre-Ramadan and post-Ramadan, but was about 30% less than loss of absolute fat mass. At 2–5 weeks after the end of Ramadan, there was a return towards, or to, pre-Ramadan measurements in weight and body composition. Conclusions: Even with no advice on lifestyle changes, there are consistent—albeit transient—reductions in weight and fat mass with the Ramadan fast, especially in people with overweight or obesity.
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Background Fasting during the month of Ramadan entails abstinence from eating and drinking between dawn and sunset and a major shift in meal times and patterns with associated changes in several hormones and circadian rhythms; whether there are accompanying changes in energy metabolism is unclear. Objective We have investigated the impact of Ramadan fasting on resting metabolic rate (RMR), activity, and total energy expenditure (TEE). Design Healthy nonobese volunteers (n = 29; 16 women) fasting during Ramadan were recruited. RMR was measured with the use of indirect calorimetry. In subgroups of participants, activity (n = 11; 5 women) and TEE (n = 10; 5 women) in free-living conditions were measured with the use of accelerometers and the doubly labeled water technique, respectively. Body composition was measured with the use of bioelectrical impedance. Measurements were repeated after a wash-out period of between 1 and 2 mo after Ramadan. Nonparametric tests were used for comparative statistics. Results Ramadan fasting did not result in any change in RMR (mean ± SD: 1365.7 ± 230.2 compared with 1362.9 ± 273.6 kcal/d for Ramadan and post-Ramadan respectively, P = 0.713, n = 29). However, controlling for the effects of age, sex, and body weight, RMR was higher in the first week of Ramadan than in subsequent weeks. During Ramadan, the total number of steps walked were significantly lower (n = 11, P = 0.001), while overall sleeping time was reduced and different sleeping patterns were seen. TEE did not differ significantly between Ramadan and post-Ramadan (mean ± SD: 2224.1 ± 433.7 compared with 2121.0 ± 718.5 kcal/d for Ramadan and post-Ramadan, P = 0.7695, n = 10). Conclusions Ramadan fasting is associated with reduced activity and sleeping time, but no significant change in RMR or TEE. Reported weight changes with Ramadan in other studies are more likely to be due to differences in food intake. This trial is registered at clinicaltrials.gov as NCT02696421.
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The study aimed to examine the effects of diurnal Ramadan fasting (RF) on substrate oxidation, energy production, blood lipids and glucose as well as body composition. Nine healthy Muslim men (fasting (FAST) group) and eight healthy non-practicing men (control (CNT) group) were assessed pre- and post-RF. FAST were additionally assessed at days 10, 20 and 30 of RF in the morning and evening. Body composition was determined by hydrodensitometry, substrate oxidation and energy production by indirect calorimetry, blood metabolic profile by biochemical analyses and energy balance by activity tracker recordings and food log analyses. A significant group×time interaction revealed that chronic RF reduced body mass and adiposity in FAST, without changing lean mass, whereas CNT subjects remained unchanged. In parallel to these findings, a significant main diurnal effect (morning v. evening) of RF on substrate oxidation (a shift towards lipid oxidation) and blood metabolic profile (a decrease in glucose and an increase in total cholesterol and TAG levels, respectively) was observed, which did not vary over the course of the Ramadan. In conclusion, although RF induces diurnal metabolic adjustments (morning v. evening), no carryover effect was observed throughout RF despite the extended daily fasting period (18·0 ( sd 0·3) h) and changes in body composition.
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Background: Ramadan fasting is associated with some lifestyle changes. A lack of nutritional needs knowledge or the improper performance of fasting, particularly in relation to time, type and amount of food intake, can cause disorders such as indigestion, bloating, constipation, headaches and other clinical problems. Objectives: To investigate the general knowledge regarding dietary factors associated with Ramadan fasting and its related complications. Patients and methods: This prospective, non-interventional, observational study was conducted from April to July, 2012 to coincide with the month before and the month of Ramadan. The initial participants were 600 fasting and 588 non-fasting people (aged 18 - 65 years, BMI 18.5 - 40 kg/m(2)) chosen by random cluster sampling in Tehran, Iran. A questionnaire of Ramadan fasting nutritional knowledge was developed and validated in a pilot study. The Likert scale was used two weeks before Ramadan and during the third and fourth weeks of Ramadan to estimate Ramadan-related complications. Seven-day, 24 - hour food recalls were used to assess food intakes. Results: The lowest level of general knowledge was identified in the context of foods associated with hunger (22.1%) and hypoglycemia (24.8%) and the highest level of general knowledge was identified in reference to unsuitable foods for Sahar (91.4%). During Ramadan, all attributed complications increased in fasting subjects (P < 0.001). High calorie, carbohydrate, fat and protein intakes in the Ramadan diet were associated with some gastrointestinal and sleep complications (P < 0.05). Conclusions: Despite the relatively high level of knowledge in the context of the general principles of a diet to prevent Ramadan-related complications, practical training in regard to the amounts of nutrients associated with Ramadan-related complications is both necessary and recommended.
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Over one billion Muslims worldwide fast during the month of Ramadan. Ramadan fasting brings about some changes in the daily lives of practicing Muslims, especially in their diet and sleep patterns, which are associated with the risk of cardiovascular diseases. Over the years, many original studies have made the effort to identify the possible impact of the Ramadan fast on cardiovascular diseases. This systematic review and meta-analysis is an attempt to present the summary of key findings from those articles and an appraisal of selected literature. A systematic search using keywords of ";Ramadan fasting" and ";cardiovascular diseases" was conducted in primary research article and gray-literature repositories, in combination with hand searching and snow balling. Fifteen studies were finally selected for data extraction on the outcomes of stroke, myocardial infarction, and congestive heart failure. The analysis revealed that the incidence of cardiovascular events during the Ramadan fast was similar to the nonfasting period. Ramadan fast is not associated with any change in incidence of acute cardiovascular disease.
Article
The aim of this study was to investigate the acute effect of hydration status on glycemic regulation in healthy adults and explore underlying mechanisms. In this randomized crossover trial, 16 healthy adults (8 male) underwent an oral glucose tolerance test (OGTT) when hypohydrated and rehydrated, after four days of pre-trial standardization. One day pre-OGTT, participants were dehydrated for 1-h in a heat-tent with subsequent fluid restriction (HYPO) or replacement (RE). The following day, an OGTT was performed with metabolic rate measures and pre- and post-OGTT muscle biopsies. Peripheral quantitative computer tomography thigh scans were taken pre- and post-intervention to infer changes in cell volume. HYPO (but not RE) induced 1.9±1.2% body mass loss, 2.9±2.7% cell volume reduction, and increased urinary hydration markers, serum osmolality, and plasma copeptin concentration (all p≤0.007). Fasted serum glucose (HYPO 5.10±0.42 mmol∙l‑1; RE 5.02±0.40 mmol∙l-1; p=0.327) and insulin (HYPO 27.1±9.7 pmol∙L-1; RE 27.6±9.2 pmol∙L-1; p=0.809) concentrations were similar between HYPO and RE. Hydration status did not alter the serum glucose ( p=0.627) or insulin ( p=0.200) responses during the OGTT. Muscle water content was lower pre-OGTT after HYPO compared to RE (761±13 g∙kg-1 wet weight versus 772±18 g∙kg-1 RE), but similar post-OGTT (HYPO 779±15 g∙kg-1 versus RE 780±20 g∙kg‑1; time p=0.011; trial*time p = 0.055). Resting energy expenditure was similar between hydration states (stable between -1.21 and 5.94 kJ∙kg-1∙d-1; trial p=0.904). Overall, despite acute mild hypohydration increasing plasma copeptin concentrations and decreasing fasted cell volume and muscle water, we found no effect on glycemic regulation.
Article
Background Overnight fasting is often prolonged before scheduled surgery, and the extent of perioperative fluid replacement may influence outcome. In clinical practice, basic requirements are estimated at 1.2‐2.0 mL·kg⁻¹·h⁻¹, but there is little contemporary clinical data on what deficits result from complete fasting. This prospective preclinical study was designed to determine total fluid loss during overnight fasting, prolonged during daytime. Methods Twenty (10 female) healthy adult volunteers, aged 24 (range 21‐46) years, fasted from 22:00 until 16:00, and had their body weight and urine output measured at predefined time intervals. Results The median (interquartile range) fluid deficits were 0.82 (0.73‐1.00) kg, corresponding to 1.26 (1.11‐1.41) g·kg⁻¹·h⁻¹ for the initial overnight fasting period, 0.59 (0.40‐0.70) kg and 0.99 (0.83‐1.31) g·kg⁻¹·h⁻¹ for the consecutive daytime period, and 1.47 (1.27‐1.64) kg and 1.19 (1.05‐1.28) g·kg⁻¹·h⁻¹ for the total period of fasting. Urine output accounted for 52% of total weight loss and was 36% of the baseline hourly level during the last four‐hour period of fasting. Conclusions Ten hours of overnight fasting in young adults induces fluid deficits at the lower limit of estimated intervals referred to in clinical practice, and hourly weight loss gradually decreases further during prolonged daytime fasting. These findings indicate that current routine procedures do slightly overestimate fluid deficits resulting from prolonged fasting in perioperative clinical practice.
Article
The pathogenesis of human obesity is the result of dysregulation of the reciprocal relationship between food intake and energy expenditure (EE), which influences daily energy balance and ultimately leads to weight gain. According to principles of energy homeostasis, a relatively lower EE in a setting of energy balance may lead to weight gain; however, results from different study groups are contradictory and indicate a complex interaction between EE and food intake which may differentially influence weight change in humans. Recently, studies evaluating the adaptive response of one component to perturbations of the other component of energy balance have revealed both the existence of differing metabolic phenotypes (“spendthrift” and “thrifty”) resulting from overeating or underfeeding, as well as energy-sensing mechanisms linking EE to food intake, which might explain the propensity of an individual to weight gain. The purpose of this review is to debate the role that human EE plays on body weight regulation and to discuss the physiologic mechanisms linking EE and food intake. An increased understanding of the complex interplay between human metabolism and food consumption may provide insight into pathophysiologic mechanisms underlying weight gain, which may eventually lead to prevention and better treatment of human obesity.
Article
Humans in modern societies typically consume food at least three times daily, while laboratory animals are fed ad libitum. Overconsumption of food with such eating patterns often leads to metabolic morbidities (insulin resistance, excessive accumulation of visceral fat, etc.), particularly when associated with a sedentary lifestyle. Because animals, including humans, evolved in environments where food was relatively scarce, they developed numerous adaptations that enabled them to function at a high level, both physically and cognitively, when in a food-deprived/fasted state. Intermittent fasting (IF) encompasses eating patterns in which individuals go extended time periods (e.g., 16–48 hours) with little or no energy intake, with intervening periods of normal food intake, on a recurring basis. We use the term periodic fasting (PF) to refer to IF with periods of fasting or fasting mimicking diets lasting from 2 to as many as 21 or more days. In laboratory rats and mice IF and PF have profound beneficial effects on many different indices of health and, importantly, can counteract disease processes and improve functional outcome in experimental models of a wide range of age-related disorders including diabetes, cardiovascular disease, cancers and neurological disorders such as Alzheimer’s disease Parkinson’s disease and stroke. Studies of IF (e.g., 60% energy restriction on 2 days per week or every other day), PF (e.g., a 5 day diet providing 750–1100 kcal) and time-restricted feeding (TRF; limiting the daily period of food intake to 8 hours or less) in normal and overweight human subjects have demonstrated efficacy for weight loss and improvements in multiple health indicators including insulin resistance and reductions in risk factors for cardiovascular disease. The cellular and molecular mechanisms by which IF improves health and counteracts disease processes involve activation of adaptive cellular stress response signaling pathways that enhance mitochondrial health, DNA repair and autophagy. PF also promotes stem cell-based regeneration as well as long-lasting metabolic effects. Randomized controlled clinical trials of IF versus PF and isoenergetic continuous energy restriction in human subjects will be required to establish the efficacy of IF in improving general health, and preventing and managing major diseases of aging.
Article
The present study focused on rapid responses of inflammation markers and insulin resistance to dietary restriction and exercise in inactive patients. 13 obese women were included during a 5-day time frame during which decreases in food intake (-1 378±298 kcal) were associated with 2 exercise sessions (80 and 40 min). Circulating inflammatory biomarkers, insulin resistance index and muscle soreness were measured in fasted conditions. Fasting plasma concentrations of CRP and insulin resistance index decreased over the period (respectively, p=0.02 and p=0.01), concentrations of IL-6 and TNF-α appeared unchanged (p>0.05). Changes in IL-6 (enhanced) and TNF-α (reduced) concentrations following the prolonged exercise differed compared to days with 40 min exercise and days without exercise (p<0.05). Muscle soreness appeared higher after the 80 min than after the 40-min exercise (p=0.01), and were related with IL-6 and CRP concentration changes. A 5-day period combining exercise and diet reduced the insulin-resistance index and the CRP fasting concentrations. The 80-min exercise enhanced IL-6 and lowered TNF-α concentration changes while days without exercise unaffected these cytokines. These exercise effects on cytokines may have benefited to the insulin resistance index. The duration and number of the exercise sessions appeared sufficient for inactive subjects to initiate health benefits without inducing negative effects on inflammation and muscle soreness. © Georg Thieme Verlag KG Stuttgart · New York.