UCLA

Meal timing may affect metabolic health given the circadian regulation of metabolism. The National Institutes of Health and the 2020-2025 Dietary Guidelines for Americans Advisory Committee have called for research on investigating the health impacts of meal timing. Nonetheless, the optimal meal timing for preventing and managing type 2 diabetes, a metabolic disease characterized by abnormal glucose metabolism, remains unknown.There is a diurnal rhythm of glucose tolerance that peaks in the morning and declines in the afternoon and evening, which is regulated by the circadian rhythm of hormonal and enzymatic processes controlling postprandial glucose levels. Additionally, arising evidence adds a nuanced understanding to early morning glucose tolerance, suggesting that it may be compromised due to elevated melatonin and cortisol levels. Given that higher postprandial glucose rise is an independent risk factor for cardiometabolic disease, assuming daily diet quality and quantity are relatively constant, eating more in late morning may lower the daily postprandial glucose rise, thereby conferring cardiometabolic benefits in preventing and managing type 2 diabetes. This dissertation utilized data from the Hispanic Community Health Study/Study of Latinos and the National Health and Nutrition Examination Survey. Regarding type 2 diabetes prevention, we found that late morning meal timing was inversely associated with type 2 diabetes risk among Hispanic/Latino adults without diabetes. Regarding type 2 diabetes management, we found that late morning meal timing was prospectively associated with lower glycosylated hemoglobin levels six years later among Hispanic/Latino adults with type 2 diabetes not on antidiabetic medications. Moreover, in U.S. adults with type 2 diabetes, late morning meal timing was inversely associated with cardiovascular disease mortality risk. In conclusion, this dissertation indicates that late morning may be a favorable meal timing for preventing and managing type 2 diabetes. Given the escalating global burden of type 2 diabetes, this dissertation holds promise in providing a novel, modifiable factor to counteract this pervasive public health issue. Future studies with repeated measures of habitual meal timing while accounting for differences in individual internal circadian time are warranted to confirm our findings.