We know from studies that lack of sleep is causally connected to many physical problems. One of the common symptoms of obstructive sleep apnea is being overweight. So then, how do sleep disorders contribute to weight gain?
Ghrelin: the Hunger Hormone
Lack of sleep increases ghrelin, and decreases leptin, both effects producing increased hunger and obesity. Leptin is the “anti-hunger” hormone. When the circadian rhythm is interrupted by exposure to light at night, gherlin is released. Ghrelin is known as the “hunger hormone” It is produced in the gastrointestinal tract and functions as a neurotransmitter. The receptor for ghrelin is found on the same cells in the brain as the receptor for leptin, the satiety hormone that has opposite effects from ghrelin.
An inverse relationship between the hours of sleep and blood concentrations of ghrelin exists; as the hours of sleep increase, ghrelin levels trend lower and obesity is less likely. Short sleep duration is associated with high levels of ghrelin and obesity.
When the stomach is empty, ghrelin is secreted. When we eat something the stomach is stretched and ghrelin secretion stops. Ghrelin acts to increase hunger and to increase gastric acid secretion and gastrointestinal motility to prepare the body for food intake.
What else does Ghrelin effect?
Beyond regulating hunger, ghrelin also plays a significant role in other systemic functions. Ghrelin influences body composition, it stimulates the release of growth hormone and regulaties the distribution and rate of use of energy.
This is just another convincing reason to get adequate healthy sleep. Light is the circadian rhythm disrupter. Avoid light disturbances during sleep: have no lights in the bed room, pull the shades down to block any outside light, wear an eye mask.
Zarouna S, Wozniak G, Papachristou
Stalo Zarouna, Psychology Department, University of Cyprus, Nicosia 1678, Cyprus.
Gahete MD, Córdoba-Chacón J, Salvatori R, Castaño JP, Kineman RD, Luque RM.
Department of Cell Biology, Physiology and Immunology, University of Cordoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), and CIBER Fisiopatología de la Obesidad y Nutrición, 14004 Córdoba, Spain.