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In the era of nutritional and wellbeing awareness, it's no secret that all the processes of the body are interconnected. 

Experts up till now have identified strong evidence to suggest that eating habits are crucial for the quality of sleep. 

But what about the other way round?

Could your sleep quality, duration, and hygiene affect how much you eat?

Sleep and Hunger Hormone

The hunger hormone found in our body is called Ghrelin.

Its main function is to increase our appetite and induce the feeling of hunger.

Ghrelin also regulates glucose homeostasis (blood sugar regulation) and promotes fat storage. 

On the other hand, a hormone called Leptin induces satiety or the feeling of fullness.

The levels of both these hormones significantly influence your eating habits.

Image: Hunger-regulating hormones

Research has shown that sleep patterns influence ghrelin levels

When a person is asleep, the body reassures the brain that the existing energy levels are sufficient for the time being.

Hence, the ghrelin levels decrease, and at the same time, leptin levels rise.

A study has found a significant association between sleep duration and leptin and ghrelin levels, independent of age, sex, BMI, and other confounding factors.  

A single night of disrupted sleep increases ghrelin levels and typically has no effects on leptin levels.

However, chronic sleeplessness results in the fall of leptin levels as well.

According to a report in the journal of the Public Library of Science, those who consistently slept for 5 or less hours a night had a significantly different profile of the hunger hormones than those who consistently slept for 8 hours.

These changes in the hormone levels ultimately lead to increased hunger and excessive eating, all of which may result in weight gain and obesity. 

An Extra Hour Of Sleep Can Help Lower Calorie Intake

A randomized clinical trial was conducted to examine the effects of sleep extension on energy intake among overweight adults.

The results, published in JAMA Internal Medicine on the 7th of February, reported that the participants who slept for an extra 1.2 hours (72 minutes) per night reduced their energy consumption by 270 kcals per day.

Details of Study Participants

No. of participants80 adult men and women
Age21-40 years
BMI (Body Mass Index)25.0-29.9
Mean sleep duration6.5 hours
RaceAsian, Black or African American, Hispanic, and White

The Study Methods

The participants used an accelerometer-based monitor with an event marker to record their sleep-wake patterns.

During the 2-week baseline, the participants followed their habitual sleep duration.

At the end of two weeks, the participants chosen for sleep extension underwent a counseling session with a sleep hygienist.

The study investigators then advised this group of participants to extend their sleep duration to 8.5 hours. 

On day 22, the participants returned for a brief follow-up and counseling session (if required).

The energy intake and storage were measured using the doubly labeled water method, a urine-based test. 

The Study Results

The Takeaway

Sleep is a vital part of maintaining a healthy lifestyle and preventing a plethora of diseases.

Those who habitually sleep for seven hours or less can benefit in terms of weight loss when they extend their sleep duration.


  1. Ghrelin, the hunger hormone, and leptin, the satiety hormone, play an important role in regulating eating behavior.
  2. Acute sleep disruption leads to increased ghrelin levels, and chronic sleep disruption leads to reduced leptin levels and increased ghrelin levels.
  3. A study published in the JAMA Network reported that increasing sleep duration by 1.2 hours can reduce energy consumption by 270 kcal/day in individuals who are habituated to <7 hours of sleep.



The Science Behind Sleep

The common ingredient in your tea, coffee, and energy drinks, caffeine, is the strongest psychoactive drug in the world. It is not a secret that caffeine helps you stay awake. But, how does it manage to do that?

Let's first look at how your brain puts you to sleep.

Adenosine triphosphate, or ATP, is the energy currency of your body. ATP is broken down into a molecule called adenosine in the brain. Adenosine moves around the neurons keeping up your energy levels throughout the day.

As the day progresses, some of these adenosine molecules exit the neurons and bind to the receptors. This causes sleepiness. There are two adenosine receptors, A1 and A2A. A1 receptors are found on neurons that keep the brain awake, and A2A receptors are found on neurons that initiate sleep

caffeine and sleep

Image: Adenosine receptors and sleep

When adenosine binds to the A1 receptor, it reduces the activity of the neurons. When it binds to the A2A receptors, it increases the activity of the receptor. The combination of this binding, along with a few other hormonal changes, makes you sleepy. When you sleep, the adenosine is slowly released from the receptors, and when there isn't enough left to bind to the receptors, you wake up from a refreshed night of sleep.

Caffeine And Sleep

Caffeine and adenosine are similar in structure. So, the caffeine can mimic the adenosine molecules and bind to the A1 and A2A receptors. However, caffeine's structure isn't identical to adenosine. As a result, it doesn't produce the "sleepy" effect.

Instead, it wards off sleepiness by preventing the adenosine molecules from binding and initiating the sleep process.

caffeine and sleep

  Image: Caffeine binding to adenosine receptors

But this effect lasts for only two to four hours, depending on how fast your body can break down the caffeine. This largely depends on your genes. When your body starts getting used to the caffeine intake, it produces more adenosine receptors to counteract the effect of caffeine. You may have to end up consuming more caffeine to stay awake!

Caffeine Withdrawal

Increased caffeine consumption leads to increased production of the receptor, which again results in increased caffeine consumption. It is a pretty vicious cycle that can make you a chronic caffeine drinker! As a result, you eventually develop caffeine tolerance. When you abruptly bid farewell to caffeine, you may end up feeling way too drowsy because of the additional adenosine receptors in the brain. This is called caffeine withdrawal.

Caffeine withdrawal is characterized by other symptoms like:

They can last up to a week till the number of receptors goes back to normal. Caffeine isn't as addicting or life-threatening compared to drugs like cocaine. People tend to have a mild physical dependence on this drug. People cannot overdose on caffeine easily. An average adult would have to have about 100 cups of coffee, which amounts to 10 grams of caffeine, to experience any lethal effects of caffeine.

The adenosine receptors are also found in the heart and kidneys. Activation of the receptors decreases the activity of these organs as well. Reduced urine output and heart rate prepare the body for a good night's sleep. However, when caffeine goes and binds instead, it results in increased heart rate and urine production. This is manifested as caffeine jitters and dehydration.

Caffeine isn't very dangerous; however, children should avoid it. Scientists haven't understood the effect of caffeine on a developing brain yet. It is also unhealthy for an adult to be consuming too much caffeine. Sleep and rest are essential for healthy brain function and well-being. 

Getting a Genetic Test

The genes that metabolize caffeine can say a lot about how much caffeine is "healthy" for you. A genetic test can help identify your caffeine metabolizing status. 

Xcode Life's Gene Sleep report profiles genes that influence sleep upon caffeine consumption. All you need is your genetic ancestry test raw data to get started!


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