"Obesity and weight gain predicted who was going to experience daytime sleepiness," said Julio Fernandez-Mendoza, assistant professor of psychiatry at the Penn State College of Medicine in the US.
"Moreover, weight loss predicted who was going to stop experiencing daytime sleepiness, reinforcing the causal relationship," Fernandez-Mendoza noted.
The association between body mass index and sleepiness was independent of sleep duration, which means that obese people may be tired during the day, no matter how much they sleep at night.
How does obesity trigger sleepiness?
The primary underlying mechanism that makes obese people feel overly tired may be associated with low-grade chronic inflammation. Simply put, fat cells - particularly from abdominal fat - produce immune compounds called cytokines that promote sleepiness, among other effects. Researchers measured self-reporting of excessive daytime sleepiness (EDS) at baseline and again an average of 7.5 years later in 1,395 men and women.
According another online health journal, WebMD, "The odds of developing excessive daytime sleepiness were nearly three times as high in depressed people and more than twice as high in obese people with sleep apnea."
Those who suffered from depression also had high incidence of EDS. Physiologic sleep disturbances, including taking longer to fall asleep and waking up in the middle of the night, explained their daytime drowsiness. These findings could lead to more personalized sleep medicine for those with EDS. Feeling overly tired during the day can reduce job productivity and increase errors and absenteeism and may lead to more serious issues like automobile accidents.
Inputs from IANS