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

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).

Inclusion criteria

• Age: 18-70 years
• BMI ≥ 25 kg/m2 (or ≥ 23 kg/m2 for Asian adults)
• Own a smartphone (Apple iOS or Android OS)
• Baseline eating window ≥ 14 h/day
• Night shift nurses and nursing assistants who are working a 12-hour night shift at least 3 days/week.
• Have been doing night shift work for at least 3 months.
• Patients on cardiovascular medications (HMG CoA reductase inhibitors (statins), metformin, lipid-modifying drugs (including over-the-counter drugs such as red yeast rice and fish oil), anti-hypertensive, drugs), are allowed
• If patients have Type 2 Diabetes, they will be included in the study if A1c is less than 9 and they are not on insulin.

Exclusion criteria

• Insufficient dietary logging on the mCC app is defined as less than 7 of 14 days of baseline of dietary logging with a minimum of 2 items a day, at least 5 hours apart.
• Type 1 Diabetes or Insulin-dependent Type 2 Diabetes.
• Use of sulfonylurea or insulin within the last 3 months (due to unknown safety with TRE)
• Use of medications that are known to cause weight loss such as SGLT2 inhibitors and GLP1 receptor agonists)
• BMI > 50 kg/m2
• Change in medications that could impact study outcomes within the past 3 months
• Change in weight of >4kg in the past 3 months
• Women who are pregnant, breastfeeding, or are trying to become pregnant during the study period. If a participant becomes pregnant during the study, they will be excluded from continuing the study.
• Systolic BP greater than 160 mmHg and/or diastolic BP greater than 110 mmHg at rest
• Fasting LDL cholesterol greater than 250 mg/dL
• Fasting triglycerides greater than 500g/dL
• Active tobacco abuse or illicit drug use or history of treatment for alcohol abuse in the past 5 years.
• Frequent (more than 4) travel involving a time zone change of more than 3 hours over the 1-year study period
• Prolonged leave from work (a continuous month or longer) during the study
• Active treatment for inflammatory and/or rheumatologic disease
• History of a major adverse cardiovascular event within the past year (acute coronary syndrome, percutaneous coronary intervention, coronary artery bypass graft surgery, hospitalization for congestive heart failure, stroke/transient ischemic attack)
• Uncontrolled arrhythmia (i.e. rate-controlled atrial fibrillation/atrial flutter are acceptable)
• History of thyroid disease requiring dose titration of thyroid replacement medication(s) within the past 3 months (hypothyroidism on a stable dose of thyroid replacement therapy is allowed).
• History of adrenal disease in the past 5 years
• History of malignancy undergoing active treatment, except non-melanoma skin cancer, in the past 5 years
• History of an eating disorder in the past 5 years
• History of cirrhosis in the past 5 years
• History of stage 4 or 5 chronic kidney disease or dialysis in the past 5 years
• History of HIV/AIDs
• Currently enrolled in weight-loss or weight-management program
• History of surgical intervention for weight management within the past 2 years, or longer if deemed unsafe following review by medical investigators
• Uncontrolled psychiatric disorder including prior hospitalization