Definite evening-type medical students gained an average of 0.88 kg compared to definite morning-type students.
Among 1300 medical students, distribution included 14.08% definite morning, 12.38% moderate morning, 28.92% intermediate, 31.46% moderate evening, and 13.15% definite evening.
Definite evening-type students reported worse sleep quality, shorter sleep duration, and higher consumption of late-night snacks.
An increasing trend of weight change was observed in students with moderate morning to definite evening chronotypes.
The odds of weight gain were higher for evening chronotype students, particularly those who had dinner at or after 6 PM, compared to morning-type students who dined earlier.
Simplified
PURPOSE: This study analyzed the differences in weight change among medical students with different and evaluated the association between chronotype and weight change after controlling for confounders.
METHODS: Using proportional stratified cluster random sampling, 1300 medical students (excluding freshmen) were selected from April to September 2021. Chronotype was assessed with the Chinese version of MEQ-5 questionnaire, categorized into five groups: definite morning, moderate morning, intermediate, moderate evening, and definite evening. The primary outcome was weight change value (kg), the difference between current weight and weight at admission; the secondary outcome was weight gain (≥10% increase from admission weight). Multiple linear and logistic regression models were used to analyze the independent association between chronotype, weight change value, and weight gain, respectively.
RESULTS: Among the 1300 medical students, the proportion of definite morning, moderate morning, intermediate, moderate evening, and definite evening chronotype were 14.08%, 12.38%, 28.92%, 31.46%, 13.15%, respectively. Definite evening-type students had worse sleep quality, shorter sleep duration, more late-night snacks, higher satiety, and lower breakfast frequency (<0.05). Compared to definite morning-type medical students, those with moderate morning, intermediate, moderate evening and definite evening chronotype showed an increasing trend of weight change (=0.044), with definite evening-type students gaining 0.88 kg on average (95% CI: 0.10, 1.65), consistent after adjusting for confounders. The association between chronotype and weight gain was similar although not statistically significant (OR=1.96, 95% CI: 0.72, 5.36). Evening chronotype with dinner ≥ 6 PM had the highest odds of weight gain compared to morning chronotype with dinner before 6 PM (OR=2.43, 95% CI: 1.07, 5.50). P P
CONCLUSION: Definite evening chronotype was associated with greater weight increase and higher odds of weight gain among medical students, especially when dinner ≥ 6 PM. These findings highlight the importance of morning chronotype and early dinner for weight control.
Key numbers
0.88 kg
Weight Change Increase
Average weight change among definite evening students.
42.38%
Weight Gain Proportion
Percentage of medical students who reported weight gain.
2.43
Odds Ratio for Weight Gain
Odds ratio comparing evening students with late dinner to morning types.
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