IS EATING CLOSE TO THE DIM LIGHT MELATONIN ONSET ASSOCIATED WITH BODY MASS INDEX?

Eating late negatively impacts health; however, few studies have examined meal timing in relation to circadian phase using objective markers. We assessed the relationships between DLMO, timing of feeding, body mass index (BMI) and body fat among a sample of adults without depression and with habitual sleep duration of at least 6.5 hours. Participants (N = 97), ages 18-50 years, completed seven days of actigraphy and food logs. Subsequently, participants received a DXA scan to assess body fat and DLMO was assessed in the clinical research unit. Participants were free of sleep, neurological, and psychiatric disorders, and did not use medications or substances that impact sleep. Multiple linear regression analyses assessed the relationships between timing of feeding relative to DLMO (calculated as DLMO - last meal), body composition, and diet while controlling for age, sex, and sleep duration. BMI was controlled for in analyses examining diet. Post-hoc analyses examined the differences among those with earlier DLMO versus later DLMO (≥10:30pm). Average time between last meal and DLMO was 2.29hrs and ranged from -6.67 to 10.33hrs. Meals occurring earlier in time before the DLMO were associated with less carbohydrate, b= −8.13, SEb=3.13, p=.01, and sugar intake, b= −4.52, SEb=1.16, p=.006. Timing of last meal relative to DLMO, was not related to BMI, body fat percentage, or Android-Gynoid (trunk/hip) Fat Ratio. When analyses were stratified by DLMO time, feeding closer to DLMO was associated with higher BMI, b= −.84, SEb=.29, p=.007, and AndGynFat Ration, b= −.03, SEb=.01, p=.01, among those with later DLMO, but not among those with earlier DLMO. In general, eating close to DLMO was not associated with BMI or body fat. However, among those with later DLMOs, eating closer to DLMO was associated with greater BMI and a greater AndGynFat Ratio. Eating closer to DLMO may impact health in groups with later DLMO, such as college students and delayed sleep wake phase. Support (If Any)