Daytime Sleep: Metabolism's Worst Enemy?

Sleep and metabolism are intricately linked. While your baseline metabolic rate will stay the same throughout the day and night, you will burn fewer calories at night because you are less active. Metabolism is the process of converting the food we eat into energy that can be used for day-to-day processes in the body. It is composed of two key parts: your baseline metabolism level, which fuels the body's daily functions, and the additional process of energy burning that occurs through exercise and physical activity.

The body's natural circadian rhythm at night plays a role in the metabolism. Your body takes cues from your environment and daily activities to keep your body chemistry on schedule. Eating is a wakeful activity, so any meals or snacks you have will cue the wakeful portion of your circadian rhythm. Conversely, slowing down your food intake at the end of the day, along with other cues, such as dimming lights and screens, sitting and physically resting, and turning down background noise and stimulus, cues a shift toward the sleep portion of your circadian rhythm.

Sleep deprivation can affect your gut biome – the bacteria in your digestive system that digest food and control metabolism. Poor or disturbed sleep can cause changes in your stomach's microbial community structure, which affects the way your body digests and metabolises food.

Research has shown that sleep deprivation commonly leads to metabolic dysregulation. Poor sleep is associated with increased oxidative stress, glucose (blood sugar) intolerance (a precursor to diabetes), and insulin resistance. Extra time spent awake may increase the opportunities to eat, and sleeping less may disrupt circadian rhythms, leading to weight gain.

In children and adolescents, the link between not getting enough sleep and an increased risk of obesity is well-established, although the reason for this link is still being debated. Insufficient sleep in children can lead to metabolic irregularities, skipping breakfast in the mornings, and increased intake of sweet, salty, fatty, and starchy foods.

In adults, the research is less clear. While a large analysis of past studies suggests that people getting less than 6 hours of sleep at night are more likely to be diagnosed as obese, it’s challenging for these studies to determine cause and effect. Obesity itself can increase the risk of developing conditions that interfere with sleep, like sleep apnea and depression. It’s not clear if getting less sleep is the cause of obesity in these studies, if obesity is causing the participants to get less sleep, or perhaps a mix of both.

Sleep deprivation can lead to increased appetite and a preference for high-calorie, high-carb foods

Several studies have also shown that sleep deprivation affects food preferences. Sleep-deprived individuals tend to choose foods that are high in calories and carbohydrates. A study in the American Journal of Clinical Nutrition found that when people were starved of sleep, late-night snacking increased, and they were more likely to choose high-carb snacks. In another study done at the University of Chicago, sleep-deprived participants chose snacks with twice as much fat as those who slept at least eight hours.

A review of 18 studies found that a lack of sleep led to increased cravings for energy-dense, high-carbohydrate foods. Sleep deprivation may affect the body's ability to convert food and fat into energy, leading to weight gain.

In addition to affecting appetite and food preferences, sleep deprivation can also impact the body's ability to process insulin, a hormone needed to change sugar, starches, and other foods into energy. Insulin sensitivity has been found to drop by more than 30% after just four days of insufficient sleep. When the body doesn't respond properly to insulin, it has trouble processing fats from the bloodstream, so it ends up storing them as fat.

Overall, sleep deprivation appears to have a significant impact on appetite and food preferences, leading to increased cravings for high-calorie, high-carbohydrate foods and a decreased ability to process and utilise energy.

Sleep affects the production of hormones that control appetite, such as ghrelin and leptin

Sleep has a significant impact on the production of hormones that control appetite, such as ghrelin and leptin. Ghrelin and leptin are two hormones that are produced at night. Ghrelin tells the body when to start eating, while leptin tells the body when to stop eating. Sleep deprivation is associated with increased levels of ghrelin and decreased levels of leptin, which means you will feel hungrier and slower to feel full.

In one study, men who got four hours of sleep had increased ghrelin and decreased leptin compared to those who got ten hours of sleep. This dysregulation of ghrelin and leptin may lead to increased appetite and diminished feelings of fullness in people who are sleep-deprived.

Sleep deprivation may also affect the body's ability to convert food and fat into energy. Research has shown that sleeping less diminishes the body's ability to break down fat into energy, leading to weight gain.

Sleep is essential for regulating the hormones that control hunger and appetite. Getting adequate, quality sleep is an important part of a healthy weight loss plan.

Poor sleep can disrupt the gut biome, which is responsible for digesting food and controlling metabolism

Sleep is an essential aspect of your body's functions, as it allows your body to rest and repair itself. Poor sleep can have a significant impact on your gut biome, which is responsible for digesting food and controlling metabolism.

The hypothalamus

Sleep is incredibly important for children and adolescents. Epidemiological studies have revealed a link between sleep deprivation and excess body weight, a phenomenon particularly pronounced in children. Insufficient sleep in youths may have adverse effects on the hypothalamus, which controls your appetite and energy use.

Ghrelin and leptin levels

Ghrelin and leptin are two hormones that your body produces at night. Ghrelin tells your body when to start eating, while leptin tells your body to stop eating. Sleep debt is associated with excess ghrelin and a lack of leptin, meaning you'll feel more hungry and slower to feel full.

Impeded digestion

Sleep deprivation can affect your "gut biome" – the bacteria in your digestive system that digest food and control metabolism. Poor or disturbed sleep can cause changes in your stomach's microbial community structure, which affects the way your body digests and metabolises food.

Energy levels

Getting quality sleep means getting more slow-wave or deep sleep, during which your body repairs itself and creates ATP – your body's energy molecule. If you sleep well, you'll feel more refreshed when you wake up, which means you're more likely to be active during the day. And activity influences your metabolism. Conversely, if you sleep poorly, you'll have less energy and therefore have a slower metabolism.

Endocannabinoid levels

Some research has shown that short sleep duration affects your body in a similar way to the activation of your endocannabinoid (eCB) system. The eCB system plays a key role in your brain's regulation of appetite since it affects your motivation and reward circuits. For people who were sleep-deprived, they have higher, longer-lasting eCB levels versus people who'd had good sleep. Those sleep-deprived people also reported feeling more hungry and less able to resist food.

Energy conversion

Sleep deprivation may affect your body's ability to convert food and fat into energy. Research has shown that sleeping less diminishes your ability to break down fat into energy – meaning your body stores it instead of consuming it. This is especially true if you don't get rest on a consistent basis.

Glucose absorption

Shortened sleeping times may impair the way your body metabolises glucose, which increases your risk of type 2 diabetes. It also results in weight gain, which can increase your resistance to insulin. Both affect the way your body absorbs and processes glucose.

Sleep deprivation may affect the body's ability to convert food and fat into energy

Sleep deprivation can have a significant impact on the body's ability to convert food and fat into energy. While the exact mechanisms are not yet fully understood, several studies have found a link between insufficient sleep and metabolic dysregulation. Here are some ways in which sleep deprivation may affect the body's energy conversion processes:

Impact on Hormones

Sleep deprivation can disrupt the body's regulation of hormones such as ghrelin and leptin, which play a crucial role in appetite control. Ghrelin stimulates hunger, while leptin promotes feelings of fullness. Sleep debt is associated with increased ghrelin levels and decreased leptin levels, leading to increased appetite and reduced satiety. This can result in overeating and weight gain over time.

Altered Gut Biome

Sleep deprivation can also affect the gut biome, which refers to the bacteria in the digestive system that are responsible for digesting food and controlling metabolism. Poor or disturbed sleep can alter the composition of the gut microbiome, impacting the way the body digests and metabolises food.

Impaired Glucose Absorption

Shortened sleeping times may impair the way the body metabolises glucose, increasing the risk of type 2 diabetes and weight gain. Sleep deprivation can lead to insulin resistance, making it harder for the body to process glucose effectively.

Energy Conversion

Sleep deprivation can affect the body's ability to break down fat into energy. Research has shown that a lack of sufficient and consistent rest diminishes the body's ability to convert fat into energy, leading to fat storage instead.

Impact on Physical Activity

Sleep deprivation can result in decreased energy levels and reduced physical activity. Feeling tired can make it harder to engage in exercise or physical activities, further impacting the body's energy expenditure and metabolic rate.

Overall Metabolic Dysregulation

Sleep deprivation has been linked to metabolic dysregulation, including increased oxidative stress, glucose intolerance, and insulin resistance. It can disrupt circadian rhythms and lead to weight gain and an increased risk of metabolic disorders.

Lack of sleep can impair the way the body metabolises glucose, increasing the risk of type 2 diabetes

Sleep disturbances are an under-recognised factor in type 2 diabetes. Sleep irregularity, insufficient sleep, and sleep disorders like insomnia and obstructive sleep apnea (OSA) are all associated with insulin resistance and diabetes.

Sleep disturbances can increase the risk of developing type 2 diabetes. Multiple studies have shown that repeated awakenings during the night, insufficient sleep, excessive sleep, and irregular sleep all promote glucose intolerance. Sleep disturbances can also worsen the condition of those who already have prediabetes or diabetes.

The impact of sleep disturbances on glycemic control is still being studied. However, some studies have shown that extending sleep duration for brief periods can improve insulin sensitivity.

Short sleepers who extended their sleep duration experienced improved insulin sensitivity. Other studies have shown that extending bedtime may reduce hunger and appetite and promote weight loss.

The treatment of OSA with continuous positive airway pressure (CPAP) has been shown to reduce glucose levels and improve glycemic control. However, the results of these studies are mixed, and compliance with CPAP is generally poor.

Health care professionals should screen patients for sleep problems and advise them on improving their sleep hygiene. This includes maintaining a regular sleep schedule, avoiding stimulants before bed, and keeping the bedroom cool, dark, and quiet.

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