(EA01-06-25) Evening Chronotypes Exhibit Reduced Odors Perception and High Calorie Intake in Late Evening

Scientific conference where the work was recently presented: ObesityWeek 2024 (The Obesity Society)

Date on which the work was previously presented at the scientific conference listed: November 3, 2024

Objectives: Evening chronotype (EC; preference for later bedtimes and activity) are susceptible to obesity due to increased calorie intake and reduced satiety after 8:00 pm (biological sleep time), and unhealthy diet intake. Odors guide food choices and exhibit circadian rhythm, yet whether diurnal perception of food smells increases intake of calories late in the day in EC remains unclear.

Methods: Healthy weight, morning chronotype (MC, n=22) and EC (n=21) participants recorded intensity ratings for strawberry (food) and tea rose (non-food) odor samples (high and low intensity) and food cravings for 3-days in a naturalistic setting at ~8:00am, 12:00pm, 3:00pm, 6:00pm, 8:00pm, and 10:00pm, using the ecological monetary assessment. A 24-h food diary were also completed.

Results: Baseline smell ability did not differ in EC vs MC, as determined by smell identification and threshold scores. Food odor was reported as less intense in EC vs MC (p=0.04) throughout the day, with a significant difference reported at 6:00pm, 8:00pm, and 10:00pm (p < 0.05). EC also reported both high and low intensity odors to be less intense (p=0.05) throughout the day. Total calories consumed after 8:00 pm was higher in EC vs MC. The % of total calories eaten between testing timepoints decreased in MC, while the slope for % total calories remained relatively stable throughout the day in EC (β = 2.21, p = 0.02). We also observed an increase in % of total calorie intake with an increase in odor intensity ratings. Percent calories consumed as total sugar and carbohydrates gradually increased in EC throughout the day (p=0.01). No significant difference in appetite ratings were observed by chronotype and time. Our findings indicate that food odors perceived as less intense in EC vs MC, with significant difference towards the end of the day.

Conclusions: This observed pattern in smell perception may contribute to higher calorie intake, increasing the risk of obesity in EC.

Funding Sources: San Diego State University University Grants Program Funds 2022