Effect of a Whole-Food Plant-Based Diet on Postprandial Sleepiness: A Pilot Study.
Level 4 - case-series / case-control
Uncontrolled single-arm before-and-after pilot study
PubMed 39554973 · doi:10.1177/15598276241262234
What was done
Ten adults (mean age 44 ± 15 years, 30% male) reporting postprandial sleepiness who habitually consumed a typical American diet transitioned to a whole-food plant-based (WFPB) diet for 21 days in an uncontrolled pilot study. Postprandial sleepiness was assessed using the Epworth Sleepiness Scale (ESS), specifically focusing on Q7 ("sitting quietly after lunch without alcohol"), Q5 ("lying down to rest in the afternoon"), and total ESS score. Weight change was also measured.
What was found
Participants showed statistically significant reductions in ESS Q7 (median change = -1, P = .012), ESS Q5 (median change = -1.5, P = .008), total ESS score (median change = -8.0, P = .006), and body weight (median change = -2.9 kg, P = .006).
Why it matters
This pilot study provides preliminary observational data suggesting that a short-term transition to a whole-food plant-based dietary pattern may reduce subjective daytime and post-lunch drowsiness.
Limits
The study is limited by an extremely small sample size (n = 10) and an uncontrolled before-and-after design, leaving it vulnerable to placebo effects and regression to the mean. Outcomes relied entirely on subjective self-report questionnaires rather than objective sleep or alertness metrics, and the concurrent weight loss leaves it unclear whether benefits were driven by dietary composition or caloric reduction.
Cited by
- supports Eating a meal promotes sleepiness in many individuals.