Shifting calorie consumption to earlier circadian times could benefit glucose homeostasis.
Researchers found that consuming the majority of daily calories later in an individual's circadian phase correlated with impaired glucose metabolism in a study of 89 health adult twins.
The study assessed dietary intake over 5 days, oral glucose tolerance test (OGTT) results, and sleep timing to explore relationships between meal timing and metabolic health. Caloric midpoint—the time when 50% of daily energy intake is reached—was used to capture eating distribution. Circadian timing was calculated based on the gap between this midpoint and each participant’s sleep midpoint, adjusted for sleep debt.
After adjusting for sex, age, daily energy intake, and sleep duration, a later circadian caloric midpoint was associated with higher fasting insulin (β = −0.259, p = .013), increased insulin resistance by HOMA-IR (β = −0.258, p = .011), and lower insulin sensitivity via the OGTT-derived Stumvoll index (β = 0.304, p = .00059). Later caloric midpoint also corresponded with higher body mass index (BMI) (β = −0.238, p = .009) and greater waist circumference (β = −0.171, p = .027), regardless of caloric intake or sleep duration. In contrast, the timing of first and last eating events showed weaker or non-significant associations after adjustment.
Participants consumed an average of 4.75 meals or snacks daily. The average caloric midpoint occurred at 15:51 (clock time) and 12:32 (circadian time), indicating a misalignment in some individuals between eating and internal circadian rhythms, noted study author Janna Vahlhaus from the German Institute of Human Nutrition.
Genetic influences on eating timing were evaluated by comparing monozygotic and dizygotic twins. Heritability estimates were high for circadian timing of the first eating event (59.2%), number of eating events (54.4%), and percent of energy intake at the last meal (59.7%). The circadian caloric midpoint had a heritability estimate of 34.5%.
Eating window duration and energy content of the last meal were not significantly associated with insulin sensitivity or glucose levels. These results differ from findings in time-restricted eating trials, where reduced eating windows were linked to improved metabolic outcomes—likely due to accompanying reductions in calorie intake. While genetic predisposition may influence individual eating patterns, shifting calorie consumption to earlier circadian times could benefit glucose homeostasis.
Future studies in larger and more diverse cohorts are needed to evaluate whether interventions targeting meal timing can improve metabolic health or reduce diabetes risk.
Full disclosures can be found in the published study.
Source: eBioMedicine