Light modulates leptin and ghrelin in sleep-restricted adults.
Level 2 - randomized trial
Individual within-subjects experimental trial in humans
PubMed 22988459 · doi:10.1155/2012/530726
What was done
In a within-subjects experimental study, adults underwent 5 consecutive days of an 8-hour sleep schedule (baseline) and 5 consecutive days of a 5-hour sleep-restricted schedule. Participants were exposed in the morning to dim light or to 60 lux of red (633 nm), green (532 nm), or blue (475 nm) light to assess changes in circulating leptin and ghrelin concentrations.
What was found
Five-hour sleep restriction in dim light significantly decreased leptin compared with baseline 8-hour sleep in dim light (t(1,32) = 2.9, P = 0.007). Relative to the 5-hour sleep dim-light condition, morning red, green, and blue light exposures significantly increased leptin (red: t(1,32) = 5.7, P < 0.0001; green: t(1,32) = 3.6, P = 0.001; blue: t(1,32) = 3.0, P = 0.005). Red and green light also significantly decreased ghrelin concentrations (red: t(1,32) = 3.3, P < 0.003; green: t(1,32) = 2.2, P = 0.04), whereas blue light did not. Absolute hormone values and baseline participant characteristics were not reported in the abstract.
Why it matters
This study suggests morning light exposure, particularly red and green wavelengths, can modulate appetite-regulating hormones that are typically disrupted by short sleep.
Limits
The abstract does not state the total sample size (n), participant demographics, order randomization, or whether these endocrine changes altered actual subjective hunger or caloric intake.
Cited by
- contradicts Blue light exposure stimulates hunger and ghrelin release.