Exploring Obesity: The Hidden Sleep Link

September 4, 2023

You sleep weird.

We’re willing to bet (no real stakes, duh) that the reason you’ve been unsuccessful in losing enough weight is because there’s something wrong with your sleep/wake cycle – that is, with your Circadian Rhythm.

First, if you’ve been struggling to get started on your weight loss journey, know that the writer empathises with you. But do keep in mind that the hardest step is the first one; things do get easier once you’ve overcome the very first hurdle of just getting started. You are capable. You got this!

Second, it’s also not entirely your fault. At least, not intentionally. To understand what we mean, let’s take a look at something called appetite-regulating hormones.

You’re A Puppet, Harry

Your hunger levels, body weight, and energy metabolism are largely controlled by hormones like Ghrelin and Leptin. The former is a hormone that induces hunger and tells the body to conserve energy, i.e., to slow down fat burning. It is also called “the hunger hormone”.

The latter tells the body that it’s eaten enough and now is the time to start using energy, i.e., to initiate fat burning. Leptin is also called “the satiety hormone”.

Another important hormone for weight and energy regulation is Insulin.  You’re probably more familiar with this one than the first two. Insulin essentially signals the body to store glucose in cells for later use, either for energy or anything else the body may need it for.

These hormones are the puppeteers holding the strings to your body weight and energy metabolism, among other functions.

  • Ghrelin is produced in the stomach when it is empty, to tell the body it is time to start feeding and store energy.

  • Leptin is produced by fat cells and signals the body to stop feeding and to start using energy.

  • Insulin is produced by the pancreas to process glucose and transfer it out of the blood and into cells.

Ideally, this is what the hormone cycle would look like:

Leptin - Ghrelin Cycle

Empty stomach stimulates ghrelin → You eat and fat+glucose increases → Fat releases leptin + Pancreas release Insulin → You stop eating + fat is burned + Glucose is transported → food is digested and stomach empties again → ghrelin is released (repeat)

Problems occur when poor lifestyle habits or illnesses lead to the dysfunction of these hormones, or your body becomes resistant to leptin or insulin.

Understanding Appetite-Hormone Resistance

Essentially, hormone resistance is what happens when the body makes the hormones – but the receptors don’t respond to those hormonal signals.

If your body’s appetite-hormone signalling is out of whack, the extent to which your body feels hungry and stores fat is affected. It can make you feel hungrier than you normally would, causing you to overeat and not feel full even after meals. This leads to habits like grazing, where you repeatedly eat food throughout the day and not necessarily because you feel hungry. It can be highly detrimental to your overall health.

Your body can become resistant to leptin and insulin, leading to metabolic dysfunction and the development of diseases like Type-2 diabetes and heart diseases.

What is leptin and insulin resistance?

Leptin resistance means there are excess fat cells in your body that are producing a lot of leptin and telling your brain to stop eating – but your brain doesn’t respond to these signals, leading to continued feelings of hunger and fat storage.

Similarly, Insulin resistance is when the pancreas creates insulin to tell your body to remove sugar (glucose) from the blood and to transfer it into cells, but the body does not respond. This leads to imbalanced blood glucose levels, and can lead to chronic diseases. Insulin resistance is one of the more common root causes of obesity and chronic illness.

Are leptin and insulin related?

Leptin and Insulin regulate each other. Which means a dysfunction in the regulation of one of these can impact the other. It should be noted that leptin resistance can be a precursor to insulin resistance.

[Note: whether insulin affects leptin in the short term is still debated, as studies have found claims for either case being true; however it is agreed that insulin does affect leptin secretion in the long term.]

Another major factor (besides glucose presence) that stimulates Insulin release is Melatonin – the sleep hormone. Bringing us to your circadian rhythm.

On The Clock – Sleep and Weight Gain

Ever wondered how your body knows when to feel hungry, sleepy, or energised and tired? 

Our bodies’ systems are regulated by a rhythmic pattern on a day-to-day basis. This biological rhythm is famously called the body’s “biological clock” or your “sleep/wake cycle”. Another term is the body’s circadian rhythm.

Your circadian rhythm responds to light and darkness, and dictates the release of melatonin (the sleep hormone) and the aforementioned appetite-regulating hormones.

This is how your body knows to eat during the daytime when it is bright and we are engaged in activities, and to suppress hunger when it gets dark – because we are sleeping and have no need to consume at this moment. Melatonin is also suppressed when it is bright, and it is released in darkness or dimness.

An altered circadian rhythm can lead to improper sleeping and eating habits, and sleep deprivation (which leads to an altered circadian cycle in turn).

Multiple studies over the years have shown that sleep deprivation leads to weight gain, among a host of other health issues. This is because sleep deprivation increases levels of the hunger-arousing hormone (ghrelin).  Indeed, sufficient and good-quality sleep is essential to physical and mental health.

Sleep is controlled by melatonin levels, which is involved in insulin regulation, which is involved in leptin-ghrelin regulation.

A faulty sleeping pattern can disrupt the body’s natural metabolic cycle. Being awake when it is dark and asleep when it is bright can throw off the leptin-ghrelin signalling of your body.

This altered hormone signalling further affects the circadian rhythm, too. Reduced sleep duration leads to reduced leptin signalling and increased ghrelin signals; meaning that insufficient sleep = more eating + fat storage. 

This pattern further leads to sleep alteration, ultimately forming a vicious and self sustaining cycle.

This could be due to the body’s increased need for energy to combat fatigue and stress, which increases with sleep deprivation. Let’s face it, all-nighters leave everyone so much more exhausted than even just a few hours of sleep would have.

Over time, the issue of weight gain continues to get worse as sleep disturbance continues.

Better sleep quality and duration are associated with higher chances of weight loss, and especially of fat loss. Studies experimented with various types of diets with different fat-carb ratios and sleep durations. It was found that those who got sufficient sleep (8-9 hours per day in bed) had an easier time losing weight than those who slept for less time.(1)

While it had been accepted that poor sleep was linked with obesity, the underlying mechanism for this lacked sufficient research. The theory of the circadian regulation of appetite hormones being responsible for changes in body weight could explain the link between insufficient sleep and obesity.

What We’ve Seen

In the experience iThrive has amassed over the years in dealing with thousands of clients, we have personally observed an improvement in people’s weight regulation by improving their circadian sleep cycles. Fixing leptin resistance can open the doors to a world of better health, and make it easier to lose weight.

And how can you fix leptin resistance? Fix your body’s internal clock that signals the release of these hormones.

Fixing Your Circadian Rhythm

This diurnal rhythm intrinsic to all of us is regulated by signals of light and darkness. Regulating the duration of light exposure, along with the kind of light you are exposed to can help with this.

Some useful methods to optimise your circadian rhythm are:

Steps to Optimise Circadian Rhythm

  1. Morning sunlight: 

Look at sunlight for at least 1 minute after waking up. Ideally, you look at the rising sun, but if you wake up post-sunrise, at least ensure to look at sunlight before you look at any kind of artificial light.

  1. No artificial lights:

Avoid looking at your phone or other screens and artificial lights for 30 minutes after waking and for 30-60 minutes before sleeping.

  1. Use Appropriate Lighting:
  • If you wake up before sunrise, use only red or yellow light bulbs until sunrise.
  • Install blue-light blocking apps on your laptop and phone, especially for evenings.
  • Use red-coloured blue light blockers once the sun goes down, especially if you are going to be on devices in the evening.
  • Only use yellow/red lights at home in the evenings.
  1. Eat Timely:
  • Eat within 1 hour of waking up. If you wake up before sunrise, then you can delay eating until 7 a.m.
  • Finish dinner before sunset. If you get hungry in the evening, you can have a teaspoon of butter or ghee (these do not evoke an insulin response)
  • Eat all meals at the same time everyday.
  1. Connect with Nature:

Be barefoot in nature for 15 minutes to ground yourself.

  1. Regulate Caffeine Consumption:

Consume caffeine only after 90 minutes of waking. Do not drink any caffeinated beverages after 12 pm.

  1. Eat Smart:

Incorporate Protein and Fat in each meal. These nutrients promote leptin regulation and use.

  1. Incorporate Sunlight with Me als:

Eat in the Sun whenever possible. If it’s too warm to eat outdoors, consider sitting by a window with the glass open.

  1. Evening Sunlight:

Try to look at the setting sun for at least 1 minute. Ideally, watch the whole sunset.

  1. Practice Sleep Hygiene:
  • Go to bed by 9.30 p.m.
  • Switch off the WiFi before sleeping
  • Ensure there are no electronic appliances or lights in the bedroom.

The Missing Link

If you’ve tried all sorts of weight loss strategies but had little to no success, go a little easy on yourself. The problem may be in your body’s internal clock that tells your body when to burn fat and when to store it.

Poor lifestyle habits can lead to Leptin Resistance – where your body ignores the signals from a hormone that says it’s time to stop eating and to start using energy. One way to fix this issue is by improving your circadian rhythm.

Since your sleep/wake cycle is essentially determined by your time spent being active in light and darkness, optimising that pattern is the best way to go. Try the tips mentioned in this article to fix your circadian rhythm along with your weight loss efforts and observe for changes in your weight loss pattern. In our experience, it has been the key to unlocking easier weight loss.

With that, we hope you will give your health journey another shot and that you have a fun-filled, productive experience!


  1. Sleep Deprivation: Effects on Weight Loss and Weight Loss Maintenance - PMC
  2. Diminished leptin signaling can alter circadian rhythm of metabolic activity and feeding | Journal of Applied Physiology
  3. Ghrelin and Sleep.
  4. Circadian Dysfunction Induces Leptin Resistance in Mice: Cell Metabolism
  5. Sleep Deprivation: Effects on Weight Loss and Weight Loss Maintenance - PMC
  6. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review
  7. 9 Hormones That Affect Your Weight — and How to Improve Them
  8. Stimulation of leptin secretion by insulin - PMC.
  9. Leptin and the regulation of body weigh.
  10. Ghrelin Hormone: Function and Definition.
  11. Regulation of Insulin Synthesis and Secretion and Pancreatic Beta-Cell Dysfunction in Diabetes - PMC.
  12. Melatonin: What You Need To Know | NCCIH.
  13. Leptin therapy, insulin sensitivity, and glucose homeostasis - PMC.
  14. Light, melatonin and the sleep-wake cycle. - PMC.
  15. Circadian dysfunction and obesity: is Leptin the missing link? - PMC

Amisha Jha

Amisha is an Economics graduate with a passion for languages, art, and writing. She is a strong advocate for mental and physiological healthcare accessibility and strives to bring more attention to the rising mental health crisis. Her personal discovery of how mental and physical ailments work together sparked a passion to learn more about health and wellness, and she enjoys writing about the same to educate those who are unaware. In her free time, you can find her writing poetry and relaxing with cats.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.