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The role of insufficient sleep and circadian misalignment in obesity

Written by: Mecene Research Team

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Published

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Time to read 8 min

Note From Dr. Pendleton


This article is my attempt at a simplified summary of a scientific paper I found interesting. I’m passionate about sharing scientific knowledge in a way that’s accessible to everyone. However, it's important to remember that many scientific studies, including this one, may not directly apply to you, let alone all people. For example, some studies are conducted on animals or involve small sample sizes, which limits the generalizability of the results. My goal is to present the information responsibly and in layman’s terms, so please keep in mind that the findings should be interpreted with care.


Medical Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read on this website. The information in this article is based on a scientific review and should not be used as the sole basis for treatment decisions. Always consult with a healthcare professional before starting any new treatment or therapy.

Overview

In the scientific paper entitled The Role of Insufficient Sleep and Circadian Misalignment in Obesity by Jean-Philippe Chaput et al., the authors explore how modern sleep patterns, including insufficient sleep and circadian misalignment, contribute to the global rise in obesity and related metabolic disorders such as type 2 diabetes and cardiovascular disease. Traditional risk factors like overeating and inactivity do not fully explain the increasing obesity rates, and this paper focuses on sleep disruptions as a significant, often overlooked cause. Chaput et al. review various studies on how poor sleep and irregular sleep cycles affect appetite hormones, energy use, and food choices, all of which can lead to weight gain and health complications.

How Sleep and Circadian Rhythms Affect Obesity

Obesity is a growing global health crisis, but it's not just caused by overeating or not exercising enough. Research shows that poor sleep and irregular sleep patterns, known as circadian misalignment, are also major contributors. These factors affect the body's metabolism, hormone levels, and overall ability to regulate weight.


Many people today miss out on the recommended 7 to 8 hours of sleep per night, disrupting the body's internal clock. This internal clock, also known as the circadian rhythm, governs the sleep-wake cycle and other essential body functions.


When it's thrown off balance, it can lead to weight gain and other metabolic issues, such as type 2 diabetes and heart disease. Understanding how sleep and circadian rhythms affect obesity gives us new insights into managing weight and improving overall health.

Man checking waist size.

Methodology

Researchers gathered and reviewed numerous human studies examining how sleep disruptions and circadian rhythms affect weight gain and metabolic health. These studies focused on critical hormones that control hunger and fullness, including ghrelin, leptin, and peptide-YY (PYY). Ghrelin is known as the "hunger hormone" because it increases appetite, while leptin and PYY help regulate feelings of fullness. The studies also examined how sleep loss and circadian misalignment impact the amount of energy the body uses (energy expenditure), food choices, and how much people eat.


The review focused particularly on adults, especially those in shift work, as this group often faces the greatest sleep disruptions. The research aimed to understand how modern work schedules, long hours, and exposure to artificial light—like from smartphones and computers—affect our natural circadian rhythms and contribute to weight gain.

Woman not fit in her jeans.

Main Findings

Insufficient Sleep

Not getting enough sleep is becoming increasingly common in today's fast-paced world. The research shows that about one-third of adults sleep less than the recommended 7 to 8 hours a night in many places, including the Americas, Europe, and Asia. This chronic lack of sleep has been shown to significantly raise the risk of obesity. As the study notes, "Short sleep duration is associated with a 38% absolute increase in the incidence of obesity." Sleep loss affects the body in several ways:


  • Hunger and Cravings: Sleep deprivation increases ghrelin levels, which stimulates hunger. At the same time, it lowers leptin and PYY levels, making it harder to feel full. This combination leads people to eat more, especially unhealthy, high-calorie snacks. The study explains, "Sleep restriction increases the drive to eat, and excess food intake is more related to cognitive control and reward mechanisms than to appetite hormones."
  • Energy Use vs. Food Intake: When people don't get enough sleep, their bodies burn slightly more energy—about 100 calories extra per day. However, they also tend to consume more than 250 extra calories per day, creating a positive energy balance. This means that even though people burn more energy when sleep-deprived, they eat more than they burn, leading to weight gain.

Circadian Misalignment

Circadian misalignment occurs when the body's internal clock is out of sync with the environment, such as when people stay up late, work night shifts, or spend too much time in front of screens. Circadian misalignment has several negative effects:


  • Reduced Energy Expenditure: When the sleep-wake cycle is misaligned, the body burns fewer calories. The study found that energy expenditure drops by 3% on average (around 55 calories less per day). Additionally, sleeping during the day rather than at night reduces the number of calories burned during sleep by 12-16%.
  • Changes in Hormones: Misalignment affects appetite hormones, leading to increased hunger and poor food choices. The review points out that "circadian misalignment reduces 24-hour energy expenditure, alters the levels of appetite hormones, and promotes unhealthier food choices." This can cause people to eat more, especially foods high in sugar and fat.
  • Shift Work and Health Risks: Shift workers, who often sleep during the day and are active at night, are at greater risk for obesity, cardiovascular diseases, and type 2 diabetes. Their eating and sleeping patterns are frequently misaligned with their internal body clocks, which contributes to metabolic disorders.

Combined Effects

When insufficient sleep and circadian misalignment happen together, the effects are even more damaging. People in this situation show higher levels of ghrelin, which increases hunger, and lower levels of leptin, which reduces appetite. This creates a perfect storm for overeating.


Additionally, people who are sleep-deprived and experience circadian disruption tend to eat later in the day, especially after dinner, when the body is less efficient at burning calories. "Later timing of food intake is associated with lower thermic effects of food," the research notes, meaning the body burns fewer calories when eating later, leading to more weight gain.

Implications

These findings highlight the need to include sleep quality and circadian health in efforts to prevent and treat obesity. Beyond diet and exercise, improving sleep and aligning sleep patterns with the body's natural rhythms are essential for maintaining a healthy weight. Key implications include:


  • Sleep Education and Public Health: Educating people about the importance of getting enough sleep could help reduce obesity rates. Simple steps like limiting screen time before bed, creating a calming bedtime routine, and ensuring a dark, quiet sleeping environment can make a big difference. The study emphasizes the need to "highlight the importance of optimal sleep and circadian health in the maintenance of metabolic health."
  • Workplace Adjustments: Workers with irregular schedules, particularly shift workers, could benefit from flexible schedules that allow them to sleep at times that align with their natural body clocks. This may help reduce the metabolic risks associated with circadian misalignment.
  • Meal Timing: Encouraging people to avoid eating late at night and consume more calories earlier in the day could improve weight management and metabolic health. Studies show that "people who consume a larger proportion of their food intake later in the day show reduced weight loss during caloric restriction," meaning that even if they eat fewer calories, late eaters are more likely to retain weight.
Woman practicing meal timing.

How Insufficient Sleep and Circadian Misalignment Increase Obesity Risk

This research demonstrates that insufficient sleep and circadian misalignment are significant factors contributing to weight gain and obesity. The body's natural rhythms and sleep cycles are crucial for regulating hunger, energy use, and fat storage. Without enough sleep or with disrupted sleep patterns, people tend to overeat and make poorer food choices, which increases the risk of obesity and related health problems.


To tackle the obesity epidemic, public health efforts must focus on improving sleep habits and circadian alignment. By making simple lifestyle changes, such as improving sleep hygiene, regulating meal times, and creating work environments that respect natural sleep-wake cycles, we can help prevent obesity and improve overall metabolic health.

Meet the Author

Dr. James Pendleton

Dr. James Pendleton is a primary care physician specializing in a naturopathic approach to family medicine. He has nurtured a family practice in Seattle, directed a VIP medical center in Abu Dhabi, published several books and scientific articles, and designed innovative nutritional supplements for manufacturers worldwide.

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