Study finds greater social jetlag linked to a later eating pattern

A 14-day UK study suggests that differences between workday and weekend sleep schedules may be linked to when people consume energy, with the clearest pattern seen later in the evening.

Study: Social jetlag predicts greater evening energy intake in a UK cohort. Image Credit: PawelKacperek / Shutterstock

In a recent study published in the journal npj Biological Timing and Sleep, a group of researchers examined whether social jetlag is associated with the timing of daily energy intake across weekdays and weekends among healthy adults in the United Kingdom.

Background

Nearly half of the general population may experience more than one hour of social jetlag, a mismatch between biological sleep timing and socially required schedules. Social jetlag has been associated with obesity, metabolic syndrome, cardiometabolic risk factors, and dietary behaviors. Circadian rhythms regulate several biological processes, including metabolism and responses to food. People with an evening chronotype typically accumulate more sleep debt during the week that may influence their eating behavior. Nevertheless, most studies on social jetlag and eating behavior are cross-sectional, and further longitudinal research is needed to clarify whether social jetlag is associated with differences in energy-intake patterns or diet quality.

About the Study

The researchers conducted a 14-day longitudinal observational study involving 101 healthy adults residing in the United Kingdom. The study included both men and women and covered two consecutive workweeks and two weekends to capture differences in eating patterns across various days. Each participant was expected to record all food and drinks consumed throughout the study. Additionally, self-reported height, weight, physical activity, smoking status, alcohol consumption, work location, and household characteristics were collected. Body mass index (BMI) was calculated from self-reported height and weight, and chronotype was assessed using the Midpoint of Sleep on Free Days Corrected for Sleep Debt (MSFsc).

Social jetlag was calculated from differences in sleep timing between workdays and free days. Individuals were divided into groups based on whether their social jetlag was less than 1 hour or more than 1 hour. Social jetlag was also studied as a continuous factor. Statistical analyses used Poisson Pseudo-Maximum Likelihood (PPML) regression models to evaluate associations between social jetlag and energy intake across different times of day. Models incorporated sex, chronotype, time of day, and relevant interactions and were adjusted for age, BMI, smoking status, alcohol intake, workplace location, and dependent children in the home.

Study Results

In this study, researchers examined 101 healthy adults, with 77.5% female participants and 22.5% male participants. The average age of participants was approximately 32.7 years, while the median social jetlag was approximately 53 minutes. Across the entire cohort, energy intake followed a consistent daily pattern, increasing from the early morning to a peak between 4:00 p.m. and 8:00 p.m., then declining later at night. Men showed a greater peak in energy intake, particularly during the early evening, than women. The level of social jetlag was associated with differences in the timing of energy intake, with patterns varying by sex and day type.

When women in the two social-jetlag groups were compared, those with less than one hour of social jetlag tended to distribute their energy earlier in the day. Among women, lower social jetlag was associated with greater energy intake in the early weekday morning. Women with more than an hour of social jetlag, by contrast, consumed more energy in the late evening. Over the weekend, women with less social jetlag consumed more energy during the late morning than those with more social jetlag. Overall, the results indicate that greater social jetlag was associated with a later distribution of energy intake in this cohort; the analyses did not establish whether total daily energy intake differed between groups.

The smaller male subgroup showed indications of a similar pattern, primarily on weekends. The biggest weekend difference was observed when men with less than one hour of social jetlag had higher energy intake in the early morning, although this difference did not reach conventional statistical significance, and significantly higher intake in the early afternoon. The early-afternoon difference was 266 kcal. Overall, the findings suggest that temporal energy-intake patterns differed between women and men, although the small male sample limits certainty about these patterns.

When social jetlag was analyzed as a continuous measure rather than by categorical groups, the overall findings showed broadly similar temporal patterns, although several estimates were not statistically significant. In women, model estimates generally indicated that each additional hour of social jetlag was associated with lower energy intake earlier in the day and greater energy intake later in the evening. The statistically significant weekday finding was a 62.5 kcal increase in late-evening energy intake per additional hour of social jetlag, with a 95% confidence interval (CI) of 5.3 to 119.7 kcal and a p-value of 0.032.

Weekend analyses showed an even stronger tendency toward reduced morning intake with increasing social jetlag. In men, weekday associations differed somewhat from those observed in women, whereas weekends showed reduced afternoon energy intake with increasing social jetlag. Each additional hour of social jetlag was associated with 128.5 kcal greater weekday late-morning intake in men, with a 95% CI of 7.9 to 249.0 kcal and a p-value of 0.037, and 147.3 kcal lower weekend afternoon intake, with a 95% CI of −269.9 to −24.8 kcal and a p-value of 0.018.

Sensitivity analyses using low, moderate, and high social jetlag categories provided additional support for the female late-evening pattern, although the male patterns were less consistent because of small group sizes. Participants with the highest levels of social jetlag were primarily responsible for the greater late-evening energy intake observed among women. Removing chronotype from the statistical models did not materially change the results, although the cohort had limited variation in chronotype.

Conclusion

The findings showed that social jetlag was associated with changes in the timing of daily energy intake. The analyses did not establish whether total daily energy intake differed between groups. People with a higher level of social jetlag tended to consume more energy in the late evening, while people with a lower level of social jetlag usually consumed food earlier in the day.

These patterns differed somewhat between women and men but remained broadly similar across the complementary statistical analyses, although the small male subgroup warrants caution. Although the observed effects were modest and unlikely to fully explain the previously reported links between social jetlag and obesity or metabolic disease, the results highlight the importance of considering meal timing alongside sleep schedules when evaluating metabolic health. However, the small, predominantly female, highly active sample and self-reported dietary data limit generalizability to the wider UK population.

Journal reference:

Flanagan, A., Fielding, B. A., Johnston, J. D., \& Winnebeck, E. C. (2026). Social jetlag predicts greater evening energy intake in a UK cohort. npj Biological Timing and Sleep, 3:34. DOI: 10.1038/s44323-026-00097-x. https://www.nature.com/articles/s44323-026-00097-x