A Nature Health study, covered this week by The Washington Post, looked at 4,793 person-nights of matched food logs and wearable sleep recordings in a largely healthy Israeli cohort. Using a causal-inference frame that controlled for the prior day’s diet and sleep, higher fiber density lined up with about 0.59 percentage points more deep sleep, 0.76 points more REM, 1.35 points less light sleep, and a nocturnal heart rate roughly 1.14 bpm lower. Greater plant diversity and whole-plant intake also tracked with calmer overnight heart rates.
Meal timing mattered differently: heavier evening meals (a larger share of daily calories in the six hours before bed) associated with about 7.7 extra minutes of total sleep but a slightly higher overnight heart rate: longer, not necessarily more restorative. Most short-term macronutrient tweaks did not show robust links. The weekend experiment is small and concrete: load lunch and dinner with fiber-dense plants (beans, greens, whole grains, nuts), keep the late snack lighter, and treat the wearable as a mirror, not a grade.