Optimization of Chrononutrition to Reduce the Risk of Disease in Shift Workers

In this randomized controlled trial, the investigators will assess the health impacts of optimizing the timing of dietary consumption in nurses and nursing assistants who work night shifts, have a habitual eating window of 14 hours or more, and elevated weight. Participants will be randomized to one of three groups: (1) dietary monitoring, (2) dietary monitoring plus 10-hour daytime time-restricted eating (TRE), or (3) TRE with a low-glycemic snack during night shifts. The study includes a 2-week screening/baseline health assessment, with follow-up health assessments at 3-, 6- (primary outcome), and 12 months.

The purpose of this study is to assess if reducing the number of hours during which participants eat each day, and consolidating dietary intake to the daytime, (with or without a low glycemic snack during night shifts) will help decrease weight and abdominal fat, improve glucose (sugar) regulation, and improve other markers of metabolic and cardiovascular health (i.e. lipid levels, inflammation markers, etc.).

Circadian clocks ("circa" means approximately and "dian" means day) are daily rhythms in physiology and behavior (activity, sleep, eating pattern) that help our body to anticipate and adapt to predictable events in the environment. These rhythms are generated and maintained by biological clocks that are present in the brain and almost every organ of our body. Remarkably, even in the absence of any timing information from a device, our body can keep track of time and thereby help us go to sleep and eat at optimum times. However, our lifestyle and work schedules can lead us to eat, exercise, and sleep at times that the clocks in our body are not prepared for. When these abnormal daily patterns continue for several weeks or years, it can affect our health in many ways including increased body weight, poor sleep, and elevated risk for various chronic diseases. Time-restricted eating (TRE), which restricts all dietary intake to a personalized consistent daily eating window to support circadian rhythms, has been shown to improve cardiometabolic health. However, TRE has not yet been assessed in people who work night shifts.

In this study, the investigators are interested in evaluating the effects of modifying eating patterns on the health of nurses and nursing assistants who work night shifts. Participants will be randomized to (1) dietary monitoring alone, or in combination with, (2) personalized 10-hour TRE (TRE), or (3) personalized 10-hour TRE with a low-glycemic snack provided to consume during night shifts (TRE-LGS). The TRE group will only be allowed water, black coffee, and tea (without any additives such as cream, sweetener including artificial sweeteners), during night shifts. The TRE+LGS group will be provided a low glycemic snack during night shifts.

The study is a year-long including a 2-week screening/baseline assessment, a 6-month guided intervention, and a 6-month self-guided intervention. Health assessments will be taken at screening/baseline, 3 months, 6 months (primary outcome), and 1 year (follow-up). Assessments will include weight (in clinic and at home), blood pressure (in clinic and at home), dietary recall (ASA24), body mass index, blood tests (biomarkers of cardiometabolic health parameters), glycemic regulation (Continuous Glucose Monitors), body composition ( duel energy x-ray absorptiometry, DXA), dietary intake (logged on the myCircadianClock smartphone app), sleep and quality of life questionnaires, and activity, sleep, and wrist temperature (actigraphy watch).