If fat is satisfying, there is a price to be paid—and not just in one's weight. Australian researchers are reporting in the journal Nutrients that a diet high in fat appears to increase daytime sleepiness, as well as poorer sleep quality at night. After electronically monitoring 1,800 men between the ages of 35 and 80 for obstructive sleep apnea and reviewing sleep and food questionnaires, University of Adelaide researchers found that even after adjusting for several factors known to affect sleep—including depression, medications, alcohol, smoking, physical activity, and waistline—the men in the top quarter of fat intake were 78% more likely to report daytime sleepiness and nearly three times as likely to have apnea compared to men in the bottom quarter.
"Poor sleep and feeling sleepy during the day means you have less energy, but this in turn is known to increase people's cravings for high-fat, high-carbohydrate foods, which is then associated with poor sleep outcomes," says study author Yingting Cao. "The poor diet-and-sleep pattern can become a vicious cycle." She goes on to tell the New York Times that the timing of the meal itself could be a mechanism, but the team didn't ask for that information. The researchers do not report whether they distinguished between types of fat—i.e. lots of bacon and burgers versus salmon and avocado—and did not study the impact on women, but they did find that the link between one's fat intake and sleep apnea was strongest in participants with the highest body mass. (American waistlines have expanded dramatically in the past decade.)