Time-of-day and Meal Size Effects on Clinical Lipid Markers.

CONTEXT

Dyslipidemia and cardiovascular disease are common in shift workers and eating at night may contribute to this pathophysiology.

OBJECTIVE

To examine the effects of eating at different times of day on lipid profiles.

DESIGN

Two 24-hour baseline days with 8 hours of sleep, 3 meals (breakfast, lunch, dinner) and a snack, followed by a 40-hour constant routine (CR) with hourly isocaloric meals.

SETTING

Intensive Physiological Monitoring Unit, Brigham and Women's Hospital.

PARTICIPANTS

Twenty-one healthy adults [23.4 ± 2.7 years, 5F].

INTERVENTION

Forty-hour CR.

MAIN OUTCOME MEASURES

A standard clinical lipid panel, consisting of total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), was assayed in blood samples collected 4-hourly across ~4 days.

RESULTS

When participants ate at night, levels of TG were similar to eating during the day, however, these levels at night were reached with consuming approximately half the calories. Additionally, 24-hour levels of TG were 10% higher when meals were consumed hourly across 24 hours compared to consuming a typical 3-meal schedule while awake during the day and sleeping at night. The endogenous circadian rhythms of TG, which peaked at night, were shifted earlier by ~10 hours under baseline conditions, whereas the rhythms in total cholesterol, HDL-C, and LDL-C remained unchanged and peaked in the afternoon.

CONCLUSIONS

The time-of-day dependency on postprandial lipid metabolism, which leads to hypersensitivity in TG responses when eating at night, may underlie the dyslipidemia and elevated cardiovascular disease risk observed in shift workers.