With overweight and obesity rates soaring in Canada, at 36 and 23 percent respectively, fingers are often pointed at technology, fast food, and sedentary lifestyles – all likely contributers to the epidemic. Research proves that sleep quality and duration are also strong determinants of weight gain and obesity, and have sparked new interest in the role of sleep in overall well-being. Studies have found that people who have short-sleep duration (5-6 hours or less) and long-sleep duration (9-10 hours or more) are more likely to be overweight, and that sleep deficiency is significantly associated with the three components of metabolic syndrome: elevated triglycerides, elevated glucose, and abdominal obesity.
The plausible reason for this finding is the alteration of hormones that occurs with long and short sleep durations. Namely, the reduction of leptin and increase of ghrelin form a hormonal profile associated with increased hunger and appetite for carbohydrate-rich foods. The same weight gain phenomenon exists among children, with “short-sleep” children twice as likely to be obese.
Lepin is from the Greek leptos :meaning thin. It is a protein hormone that has a key role in regulating energy intake and energy expenditure. It acts as a biomarker for body fat (adiposity signal), regulates individual energy balance, and regulates against underfeeding or overfeeding. It binds to receptors in a specific brain centre (the arcuate nucleus) and signals satiety (adequate food intake).
Ghrelin is probably from the Greek ghre: meaning to grow. It is a circulating protein “hunger hormone” that increases food intake and increases fat mass by an action exerted at the level of the hypothalamus (the main “thermostat “ of the brain). This hormone is produced by specialized cells in the stomach, and secretion is stimulated as the stomach becomes empty. As it is released, it stimulates other systems, including the mesolimbic reward centres, which increases the urge to eat. Ghrelin is considered to be the “counterpart” of leptin .
The relationship between weight gain and sleep deficiency does not contain itself to these two issues alone. Rather, as individuals gain weight, especially in the trunk and neck area, their risk of sleep-disordered breathing escalates due to compromised airway function. Obstructive Sleep Apnea (OSA), a disorder characterized by a blockage of the respiratory tract causing bursts of brief but repeated wakefulness during sleep, is most common in overweight people, and if left untreated, can lead to more devastating conditions including diabetes, high blood pressure, and stroke. Also, the reduction in sleep quality can result in excessive daytime sleepiness; and the less rested and refreshed someone is, the less likely they will be to exercise and eat properly. This has shown to be especially tru in the shift-work population.
Weight loss can significantly minimize and even eliminate OSA symptoms in obese individuals. The trouble is, persistent sleep disruption from repetitive apneas throughout the night throw-off the ghrelin and leptin regulatory system, and reduce daytime energy to the point that actually tips the balance in favour of further weight gain! Correcting the sleep-disordered breathing can be the first step (for some patients) in permanently reducing weight, and adopting of a healthier life style.