The Feasibility of Overnight Time Restricted Eating and Impact on Glucose Levels in Shift Workers

The aim of this clinical trial is to assess whether it is feasible for shift workers to follow a time-restricted eating diet. The trial will investigate the impact of time-restricted eating on blood glucose levels during day and night shifts both with and without the time-restricted eating diet.

The trial aims are:

* Is it feasible for shift workers to adhere to a night time time-restricted eating protocol?
* How does time-restricted eating affect blood glucose levels during the day and night shifts and over the whole day?

Shift work is an essential component of modern workforces, with about 20% of the workforce regularly engaged in shift work. Research has shown shift workers are at higher risk of chronic diseases, including cardiometabolic disease, compared to day-only workers. Specifically, evidence shows eating overnight significantly increases the risk of metabolic syndrome. We also know eating patterns of shift workers and non-shift workers are different with evidence from our research showing shift workers engaged in night shift change their eating behaviors compared to day shifts. With a substantial proportion of the workforce involved in shift work, understanding the health challenges is crucial for developing targeted interventions and promoting a healthier shift working population.

Despite the need for behavioural eating interventions in shift workers, there is a lack of studies examining how these eating interventions would be implemented in real world contexts. Some dietary interventions related to quantity, quality and timing of food in shift workers have been reported, including limiting the quantity of food with various macronutrient restriction and low-calorie meal replacements, improving the quality of food with dietary advice/counselling, and promoting healthier food choices with variable results.

With recent recognition of the timing of food consumption being an important factor of metabolic regulation, time restricted eating (TRE) offers a viable strategy for improving metabolic health. TRE is a chrono-nutritional strategy involving close alignment of meal timing with typical circadian physiology over 24-hour periods. Typically, this involves an eating window of approximately 8 hours, with no eating during the night. Evidence shows TRE improves alignment of the fasting/eating cycle with the central circadian pacemaker and initiating nutrient-sensing pathways to ensure nutrient homeostasis. Research has shown TRE is an effective chrono-nutritional intervention for weight reduction, improvements in HbA1c and insulin levels, reduced insulin resistance or enhanced insulin sensitivity, improved glucose tolerance and reduced mean fasting glucose and improved quality of life. However, using TRE has not been examined extensively in shift workers in real world settings.

A recent narrative review found only three studies had investigated TRE as a diet strategy for shift workers under real-life conditions and these studies were conducted in populations with limited exposure to shift work situations (e.g. rotating shift work). Therefore, research is required that investigates the feasibility of TRE during night shifts in rotating shift workers.

Eligibility Criteria:
Inclusion Criteria:

* Healthcare professionals engaged in rotating shift work, including night shifts;
* Aged 23-60 years;
* At least 12 months experience in shift work;
* Willing to wear continuous glucose monitor sensors;
* Willing to engage in time restricted eating.

Exclusion Criteria:

* Diagnosis of diabetes (Type 1 or 2), any bariatric surgery, coeliac disease, inflammatory bowel disease, endocrine disorders affecting glucose metabolism, current or history of eating disorder, any liver, kidney, or coronary heart disease, obese (BMI\>35) or underweight (BMI\< 18) or any severe or unstable chronic medical conditions or cancers;
* Currently taking medications known to interact with glucose metabolism, i.e. thyroxin, insulin sensitizers, glucocorticoids, or anti-depressants, weight loss medication;
* Undertaking current structured or restrictive dietary plan;
* Shift workers who routinely do not eat between 23:00 and 06:00 hours during night shift;
* Current or planned pregnancy or currently breast feeding;
* Consume three or more standard alcohol containing beverages on a single occasion almost every day;
* People who identify as having significant caffeine dependency and are unwilling to limit intake of calorie free energy drinks;
* People with planned travel over time zones during the study period
* Any contraindication to use of Abott FreeStyle Libre Pro glucose sensor (eg prescription of vitamin C, Salicylic acid or paracetamol - to be reviewed by study clinician).