Research studies have shown that reduced sleep amounts can impact food intake and weight. However there is relatively little information on how food intake could impact sleep. Apparently much of the work has focused on self-reported diet and self-reported sleep - in other words, not much has been done in a controlled, monitored environment.
This study attempted to assess whether sleep patterns were different after periods of controlled feeding versus ad libitum feeding - this means that one group was given exactly the same food. The other group was given $25 to buy whatever food they wanted. The controlled feeding was on days 1-4 and the ad libitum feeding on days 5 and 6. The participants sleep was monitored each night with a sleep study.
The results showed that ad libitum food intake was associated with a decrease in slow-wave (the deepest level) sleep and an increase in the time it takes to fall sleep. The greater intake of saturated fats and a lower intake of fiber were also associated with less deep sleep. Additionally increased intake of both sugar and non-sugar/non-fiber carbohydrates was associated with more arousals during sleep. The authors speculate whether a diet rich in fiber with reduced intake of sugars and other non-fiber carbohydrates maybe as useful tool to improve sleep depth and architecture in individuals with poor sleep.
These results are interesting, but the actual data shows what I consider to be small effects. The decrease in slow-wave sleep went from 29.3 minutes to 24.6 minutes per night. This may be statistically significant, but I wonder if this is really clinically significant. The time it took to fall asleep went from 16.9 minutes to 29.2 minutes - arguably a more noticeable change. Of note, there was no subjective evaluation of the patient's perceived sleep quality changes with the two different diets.