By Leptin and ghrelin are two key hormones that regulate hunger and energy balance. Leptin suppresses appetite, while ghrelin stimulates it. Their levels fluctuate in response to food intake, energy status, and various physiological processes—including sleep. Sleep disorders can disrupt the balance of these hormones, leading to increased hunger, cravings, and weight gain. This article explores where these hormones are produced, how sleep disorders affect their regulation, and the mechanisms through which they contribute to weight gain.
Leptin: The Satiety Hormone
Production and Function
Leptin is primarily produced by adipocytes (fat cells) and is released into the bloodstream in proportion to the amount of fat stores in the body (Zhang et al., 1994). It acts on the hypothalamus, the brain’s appetite-regulation center, to reduce hunger and increase energy expenditure (Friedman & Halaas, 1998). When leptin levels are high, the brain perceives that the body has sufficient energy, reducing food intake.
Leptin and Sleep
Sleep deprivation is associated with reduced leptin levels, leading to increased hunger and food intake. Studies have shown that individuals who sleep less than 6 hours per night have significantly lower leptin levels than those who get 7–9 hours of sleep (Spiegel et al., 2004). This creates a state where the brain perceives an energy deficit, triggering increased appetite despite adequate energy stores.
Ghrelin: The Hunger Hormone
Production and Function
Ghrelin is primarily secreted by the stomach, particularly by the enteroendocrine cells in the gastric fundus. It stimulates hunger by acting on the hypothalamus, increasing appetite and promoting food intake (Kojima et al., 1999). Unlike leptin, ghrelin levels rise before meals and decrease after eating.
Ghrelin and Sleep
Sleep deprivation has the opposite effect on ghrelin compared to leptin—it increases ghrelin levels, leading to heightened hunger and cravings, particularly for calorie-dense, carbohydrate-rich foods (Taheri et al., 2004). One study found that after just two nights of sleep restriction (4 hours per night), ghrelin levels increased by 28% (Spiegel et al., 2004).
How Sleep Disorders Disrupt Leptin and Ghrelin Balance
1. Sleep Deprivation and Increased Caloric Intake
- Chronic sleep deprivation leads to lower leptin and higher ghrelin levels, creating a state of heightened hunger and reduced satiety.
- Sleep-restricted individuals tend to consume more calories, particularly from high-carbohydrate and high-fat foods, due to increased reward sensitivity in the brain (Greer et al., 2013).
2. Obstructive Sleep Apnea (OSA) and Weight Gain
- Individuals with OSA experience frequent awakenings and poor sleep quality, which alters leptin and ghrelin regulation.
- Studies show that people with OSA often have leptin resistance, where leptin levels are high but the brain does not respond to them properly, leading to persistent hunger and weight gain (Phillips et al., 2000).
3. Shift Work and Circadian Misalignment
- Shift workers often experience metabolic disturbances due to irregular sleep patterns, leading to elevated ghrelin and reduced leptin levels.
- This disruption is linked to an increased risk of obesity and metabolic syndrome (Garaulet et al., 2010).
How Leptin and Ghrelin Contribute to Weight Gain
1. Increased Appetite and Cravings
- Higher ghrelin levels and lower leptin levels drive excessive hunger, leading to overeating and weight gain.
2. Decreased Energy Expenditure
- Leptin normally promotes caloric expenditure, but when leptin levels are low (due to sleep loss), the body conserves energy by reducing metabolic rate, making weight gain more likely (Van Cauter et al., 2008).
3. Impaired Fat Metabolism
- Sleep-deprived individuals show increased fat storage, particularly visceral fat accumulation, which is associated with insulin resistance and metabolic diseases (Nedeltcheva et al., 2010).
Conclusion
Leptin and ghrelin are powerful regulators of hunger, and their balance is crucial for maintaining a healthy weight. Sleep deprivation and sleep disorders disrupt this balance, leading to increased appetite, reduced satiety, and weight gain. Improving sleep quality and maintaining consistent sleep patterns can help restore hormonal balance and support healthy weight management.
References
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Friedman, J. M., & Halaas, J. L. (1998). Leptin and the regulation of body weight in mammals. Nature, 395(6704), 763–770.
Spiegel, K., Tasali, E., Penev, P., & Van Cauter, E. (2004). Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine, 141(11), 846–850.
Kojima, M., Hosoda, H., Date, Y., Nakazato, M., Matsuo, H., & Kangawa, K. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature, 402(6762), 656–660.
Taheri, S., Lin, L., Austin, D., Young, T., & Mignot, E. (2004). Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased BMI. PLoS Medicine, 1(3), e62.
Greer, S. M., Goldstein, A. N., & Walker, M. P. (2013). The impact of sleep deprivation on food desire in the human brain. Nature Communications, 4, 2259.
Phillips, B. G., Kato, M., Narkiewicz, K., Choe, I., & Somers, V. K. (2000). Increases in leptin levels, sympathetic drive, and weight gain in obstructive sleep apnea. American Journal of Physiology-Heart and Circulatory Physiology, 279(1), H234-H237.
Garaulet, M., Gómez-Abellán, P., Alburquerque-Béjar, J. J., Lee, Y. C., Ordovás, J. M., & Scheer, F. A. (2010). Timing of food intake predicts weight loss effectiveness. International Journal of Obesity, 37(4), 604-611.
Van Cauter, E., & Knutson, K. L. (2008). Sleep and the epidemic of obesity in children and adults. European Journal of Endocrinology, 159(1), S59-S66.
Nedeltcheva, A. V., Kilkus, J. M., Imperial, J., Schoeller, D. A., & Penev, P. D. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine, 153(7), 435-441.
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