Indulging in a plate of greasy deliciousness (here’s looking at you, French fries) might mess with more than just your weight: Eating fatty foods might make you sleepier during the day, according to new research that will be presented next month at SLEEP, the 27th annual meeting of the Associated Professional Sleep Societies LLC in Baltimore, Maryland.
Researchers from Penn State College of Medicine asked 31 healthy, non-obese participants—none of whom have sleep apnea—to spend four nights in a sleep lab. They recorded their daytime sleepiness (how easy it was to fall asleep, not how sleepy they felt during the day), as well as their diets. Participants who consumed more fat fell asleep faster during the day than those who consumed more carbs—and this was after they adjusted for gender, age, BMI, total sleep time, and total caloric intake. There wasn’t any association between how much protein participants ate and their daytime sleepiness. This suggests that fatty dishes may make you feel sleepier, while eating carbs may help you feel more alert, say researchers.
The reasons for these associations are unclear, says researcher Julio Fernandez-Mendoza, PhD, a psychologist with the Sleep Research & Treatment Center in the Department of Psychiatry at Penn State College of Medicine.
One possibility, though: Eating foods that are high in fat may boost certain digestion- and metabolism-related hormones—which, in turn, may increase sleepiness, he says. On the other hand, eating more carbs and less fat might boost your glucose levels, giving your body more fuel to use for energy. However, Fernandez-Mendoza stresses that this is preliminary data—meaning you shouldn’t go crazy with the carbs. In fact, it’s important to note that these participants were not bingeing or even overeating. They were eating normally, but consumed different amounts of protein, fat, and carbs.