The investigators will conduct an open label, experimental medicine study exploring the acute metabolic impact of night-shift compared to day-shift work in NHS healthcare workers. Employees who are scheduled to work both day and night shifts will be recruited and identical metabolic investigations will be performed in the same participant following at least 3 consecutive day and night-shifts respectively. These investigations will take place at the Clinical Research Unit (CRU) in Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM) at Churchill Hospital. The order of post-day and post-night shift investigations will be randomly determined and there will be a 2-week minimum interval between both sets of investigations. Participants will complete a self-reported food diary before and during each set of shifts (both day and night) and will have wrist-watch actigraphy performed throughout the entire study period in order to measure sleep and activity parameters. All study visits and investigations will commence at the CRU at 8am and will include a 2-step hyperinsulinaemic euglycaemic clamp with stable isotope infusions.

Inclusion Criteria:

• Male or female
• National Health Service (NHS) worker with rotating night and day shift working patterns
• Age 18-75 years

Exclusion Criteria:

• A diagnosis of type 1 or type 2 diabetes
• Pregnancy
• A blood haemoglobin <120mg/dL
• History of alcohol use disorder or a greater than recommended alcohol intake (Recommendations > 21 units on average per week for men and > 14 units on average per week for women)
• Other conditions or co-morbidities that in the eyes of the investigators may affect data collection
• Any condition in the opinion of the investigator that might impact upon safety or validity of the results
• Primary sleep disorder
• Current glucocorticoid use
• Current melatonin use
• Patients with known non-alcoholic steatohepatitis or advanced hepatic fibrosis/cirrhosis

• NHS worker with rotating night and day shift working patterns