The Role of Sleep in Weight Management
The relationship of sleep to obesity and weight
regulation is both an interesting and important topic. Findings from the past
several years demonstrate that the quality of one’s sleep – either good or bad
– influences and affects the body’s metabolic processes as well as an
individual’s behavior. The rapidly growing interest in sleep medicine is a
result of the increasing acknowledgment that sleep serves as an important
modulator and/or mediator of physiological functions. Not only are there
associations between sleep and many of the endocrine systems that modulate
nutrient metabolism, but the influence of sleep and sleep patterns is related
to many of the neuroendocrine factors expressed during childhood and
adolescence and their influence on these systems.
More recently, sleep disorders have been shown to be
associated with an increase in weight gain, which adds to the increasing
concern about the growing obesity epidemic. There are high prevalences of
obesity as well as sleep disturbances in industrialized populations, and data
indicated that 6.5% of school children reported having a sleeping problem.
Undoubtedly, a lack of sleep could affect different neuroendocrine systems of
growth, reproduction, and metabolism. The most concerning matter based on recent
scientific data is that not only adults but also 31.8% of children and
adolescents sleep less than the minimum sleep duration of 7 hours at 5 years of
age according to sleep standards, with a concomitant risk of hormonal
dysregulation. Thus, as with many other hormones, disturbances in sleep
duration and patterns during childhood apparently have long-term consequences
for metabolic and neuroendocrine function. It's important to emphasize that not
only are humans wired to need that much sleep, but there is also a significant
prevalence of solutions for the problem that is plaguing the largest sector of
society.
1. The Impact of Sleep Deprivation on Weight Gain
Sleep is an essential component of a healthy lifestyle
and overall wellness. There is strong evidence to support the association
between inadequate sleep and weight gain. Several studies have demonstrated
that prolonged sleep disturbance and shorter sleep duration are linked to
weight gain and an increased risk of obesity. Proposed mechanisms for the
relationship between inadequate sleep, weight gain, and obesity include
psychological and physiological dysregulation of hormonal modulation of food
intake, leading to a greater increase in caloric intake, particularly from
high-calorie foods. Other explanations include fatigue and decreased physical
activity in sleep-deprived individuals. A large body of epidemiological
research has linked shorter sleep duration, altered sleep architecture, and
reduced rapid eye movement (REM) sleep with an increased risk of weight gain
and obesity.
It has been found that individuals with short sleep
duration and suboptimal sleep quality consume a greater percentage of calories
from fat and added sugars. Sleep deprivation may induce a shift in the
proportion of calories consumed towards more high-fat and high-carbohydrate
food choices, leading to weight gain and the development of obesity. Several
studies have shown that physiological mechanisms influence eating behavior, the
main pathway for weight control. There is considerable and increasing interest
in this among sleep researchers, due to evidence on how sleep deprivation
influences eating behavior and physiological systems involved in body weight
regulation. Sleep loss may not only affect food intake but also the storage of
food as adipose tissue, mediated by hormonal changes, alterations in glycemic
control, and sympathetic nervous system activity that occur when sleep is
reduced or disrupted.
The literature on sleep deprivation has shown that
sleep loss, both acute and chronic, alters the levels of appetite-regulating
hormones, an appetite-stimulating hormone, and an appetite-inhibiting hormone.
Obesity is associated with elevated levels of ghrelin, increased appetite, and
sleep disturbances characteristic of sleep deprivation, insufficient sleep, and
insomnia. Ghrelin, leptin, and their changes during the sleep-wake cycle are
potential pathways explaining the relationship between sleep and weight
control. Obese individuals often show decreased nocturnal leptin levels, and
sleep deprivation is associated with a further reduction in leptin. The
literature suggests that chronic sleep loss is an obesity risk factor for the
general population as well as for specific vulnerable groups such as shift
workers and those with sleep disorders. Researchers have reported that time to
fatigability while doing moderate activities greatly increased, thus the amount
of physical activities performed decreased, and dieters might compensate by
consuming more calories. Sleep-deprived individuals could be opting for more
low-effort, low-excitement sedentary activities. The relationship between sleep
and obesity, mainly sleep-reducing mechanisms, is complex, resulting from
diverse pathophysiological pathways, behavioral, and psychological factors. It
is important for weight control that available energy is not stored as fat in
our body, with one way to ensure this being that the excess energy contained in
food is dissipated in physical activity. The level of physical activity is
regulated by several hormones, leading to alterations in glucose-insulin
control and suppression of cardiac pulmonary function, thus promoting sleep
deprivation. Therefore, adequate sleep is an important lifestyle factor for
weight control and the prevention of obesity.
2. Mechanisms Linking Sleep and Weight Regulation
Multiple biological and physiological systems link
sleep with weight regulation. One important mechanism is the role of the
circadian rhythm in regulating metabolism and appetite. Disturbance of the
circadian rhythm and its synchronization with the light-dark cycle due to poor
quality sleep, shift work, or an unhealthy lifestyle can lead to metabolic
disturbances. It can cause changes in leptin, ghrelin, and other hormones
regulating appetite and energy metabolism. Moreover, sleep helps increase
insulin sensitivity and glucose metabolism while reducing fat storage. Good
quality and good length of sleep periods facilitate triacylglycerol metabolism
and beta-oxidation by 20-30%. Of note, sleep is not only a time of rest, but it
is also a time when human growth hormone is secreted, which helps generate new
cells and repair damaged ones while reducing the breakdown of proteins.
Furthermore, physical performance depends on sleep; exercise capacity is
reduced in the presence of even mild to moderate sleep deprivation. All these
mechanisms impair the regulation of body weight.
Multiple hormonal and neurotransmitter systems link
sleep with weight regulation. Leptin, an anorexigenic hormone decreasing
appetite, is reduced in individuals with chronic sleep deprivation, while
ghrelin, an orexigenic hormone that increases appetite, is increased. Sleep
deprivation and changes in sleep architecture are also associated with low
levels of serotonin metabolites and other stress hormones, such as cortisol and
norepinephrine. It is of interest that some studies have reported a link between
sleep duration or quality and mood. Short sleepers report levels of stress in
daily life significantly higher than those reporting longer sleep. Moreover,
sleep is important to maintain a sense of well-being and mood regulation, and
longer sleep is associated with lower stress ratings. Despite inconsistent
results, some studies have reported that short sleepers eat more due to
increased stress. Overall, much evidence from different research groups is
consistent in indicating an association between short sleep, occurring either
in a circadian context or due to lifestyle factors, weight gain, obesity, and
disturbed appetite regulation. In adults, both cross-sectional and longitudinal
studies suggest that a sleep duration of 5 hours per night increases the risk
of developing overweight or obesity.
3. Practical Strategies for Improving Sleep to Support Weight Management
From implementing small behavior modifications to
participating in relaxation and meditation techniques, there are many practical
strategies proposed to improve sleep. These strategies suggest beginning by
regulating the sleep/wake cycle to one’s natural preference. Feeling naturally
sleepy in the target bedtime window may foster deeper sleep opportunities.
Personal timing may be dictated by one’s exposure to internal lighting and
routine sleep schedules. This may also be influenced by individual lifestyle factors,
such as occupation and age. Using an individual sleep diary or habitual sleep
log can facilitate identifying natural hours of sleepiness. One must wake at
the same time regardless of bedtime and be consistent all week, including
weekends. Sleep diary data can help make small behavior changes to create
sleepiness during the new desired hours for sleep. Finally, pre-bedtime
relaxation or a routine that supports internalization may facilitate sleep.
To help improve sleep, one must have a sleep-conducive
environment, promote wake-sleep promoting lifestyle changes, and develop
positive beliefs around sleep. The role of the environment, including light
exposure and temperature, is important for improving sleep. The sleep
environment should be conducive to sleep in terms of light elimination and
keeping a cooler temperature. The temperature of the room is one of the most
important aspects of a successful sleep environment. An uncomfortable
temperature may result in decreased deep sleep, which may lead to more body
fat. If it is too cold or warm for sleep, good sleep is less likely to occur.
Most experts advise temperatures between 60 and 67°F to generate satisfactory
sleep. Depth of sleep, especially the last sleep cycle, helps regenerate
tissues and muscles, decreases cortisol, helps release human growth hormone,
and contributes to burning body fat.
4. Conclusion and Future Directions
The purpose of body weight regulation is to maintain
an appropriate level of energy balance. While the inputs and outputs for this
system are obviously related to diet and exercise, respectively, other
behaviors have been shown to significantly influence energy regulation. One of
these behaviors is sleep. Although it is only one part of the energy balance
equation, it may be an increasingly critical factor due to the decline in
average hours of sleep that people are obtaining. Although a simple solution
such as 'sleep more = lose weight' would be attractive, it is likely too
simplistic as acute detriments in other behaviors, such as diet or exercise,
can be overcome with concerted effort. The next steps in understanding the role
sleep can play in the obesity epidemic may be to determine what type of person
is most likely to benefit from getting more sleep in terms of body weight
regulation and to induce further research by reviewing these options with
mechanistic studies.
Research discusses associations and observations
between sleep patterns and weight outcomes. These studies have provided useful
information in the epidemiology of sleep and obesity; nonetheless, it is time
for intervention studies to help determine whether or not these associations
are causative in nature. In addition, these studies can help allocate funds
effectively since those most likely to benefit from extra sleep in terms of
weight management should be targeted, particularly if short sleepers are not more
likely to lose weight. Further, it will be imperative to ask whether or not
extra sleep can lead to beneficial health and/or weight changes in patients
that are obese. Although not specifically addressed, some individuals are
already seeking professional sleep counseling for weight loss assistance,
suggesting that answers to these questions are needed in a clinical setting. It
is unlikely that sleep will ever become the next successful diet formula;
however, until all appropriate information can be obtained, it seems logical
that all weight management counseling regimes encourage at least maintaining,
or more realistically finding a way to pursue, an appropriate nightly bout of
sleep.