None listed
Conditions
Brief summary
The prevalence of type 2 diabetes and obesity are rising at alarming rates. Across Australia, these chronic diseases account for billions in health care costs and lost productivity. Rates of type 2 diabetes and obesity are high among shift workers, even after controlling for lifestyle and socioeconomic status. Shift workers experience poor timing of their body clocks to the daily light/dark cycle, and they show abnormal metabolic responses, including insulin resistance and glucose intolerance. Simulated shift work studies in rodents provide a link between timing of meals and metabolic processes: withholding feeding during 'night-shift' prevents the adverse metabolic effects of simulated shift work. Whether this strategy is effective in humans remains to be demonstrated. Our preliminary data from humans in several laboratory studies indicate that meal timing does play an important role in metabolic disturbance. Indeed eating at night, when the body is primed for sleep, seems to underlie an increase in metabolic disturbance that could predispose them to chronic disease. To test this, we will measure metabolic markers in healthy men and women studied under simulated shift work conditions, where we will keep daily energy intake constant but vary meal times. We propose that by simply altering the timing of meals we will be able to mitigate the negative metabolic consequences of shift work. These results could be readily translated to existing dietary guidelines, industry recommendations and workplace policy reducing the significant and increasing burden of metabolic disease in shift workers and the wider community.
Interventions
A simulated shift work protocol, with one 8h night time baseline sleep, followed by 4 consecutive days of simulated shift work (sleep from 10:00-16:00 each day), and an 8h night time recovery sleep on day 6. An OGTT will be conducted pre and post simulated night shift and serum samples will be collected to assess markers of metabolic risk . During simulated night shift (22:00-06:00) participants completed a number of performance based assessment tasks including simulated driving and a neural beh
A simulated shift work protocol, with one 8h night time baseline sleep, followed by 4 consecutive days of simulated shift work (sleep from 10:00-16:00 each day), and an 8h night time recovery sleep on day 6. An OGTT will be conducted pre and post simulated night shift and serum samples will be collected to assess markers of metabolic risk . During simulated night shift (22:00-06:00) participants completed a number of performance based assessment tasks including simulated driving and a neural behavioural test battery. A parallel study design was implemented, whereby participants were randomly allocated to one of three conditions; meal at night, snack at night, or control. These meal schedules were provided on days 3-6 (simulated shift schedule days). On Day 1 (adaptation), Day 2 (baseline) and Day 7 (recovery), a standard meal schedule was adhered to (morning breakfast meal, noon lunch meal and evening dinner meal). Meals: Meal at night condition- morning 07:00 (toast, cereal etc), late afternoon 19:00 (sandwiches etc) and night 01:30 (mixed dishes, salad, veg etc); Snack at night condition- morning 07:00 (toast, cereal etc), afternoon 17:00 (sandwiches etc), late afternoon 19:00 (mixed dishes, salad, veg, etc) and night 01:30 (fruit, crackers, etc). The diet is a standardised diet typical of the Australian diet. The energy content of the meals was based on individual daily dietary energy requirements (kJ) calculated using the Harris Benedict equation with a light/sedentary activity level (laboratory condition). Energy intake was consistent across conditions per 24 hour period. All food provided was weighed and recorded pre and post consumption. Participants were allowed access to water ad libitum. During the protocol participants were supervised by at least two research assistants at all times. A combination of actigraphy watches and polysomnography were used to monitor sleep. Physical activity was kept to a minimum in the laboratory.
Sponsors
University of South Australia
Study design
Allocation
Randomised controlled trial
Primary purpose
Prevention
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
Adults aged 18-45 years, BMI normal to overweight (20-29kg/m2), non-smoker, low alcohol (less than or equal to 2 standard drinks/ day) and caffeine consumption (less than or equal to 2 cups/ day), normal sleep/wake pattern (habitual sleep duration between 7-8 hours a night), stable weight over the preceding 3 months, competent written and spoken English.
Exclusion criteria
Subjects who report one or more of the following: habitual napping (more than 1 per week), score of less than 31 or more than 69 in the morningness- eveningness questionnaire, significant depression or physical illness, established using clinical history and Beck Depression Inventory (score equal to or more than 14), food difficulties (example: gluten intolerance or restrained eaters) measured by clinical history, use of medications, including injected, topical or inhaled glucocorticoids, previous shift work history, sleep disorders, history of medical conditions; cardiovascular disease, neurological disorder, kidney disease, liver disease, clinically significant values (as determined by the reviewing study physician) for any hematology or chemistry parameter. Reviewing study licensed physician may opt to repeat any clinically significant tests and include volunteers whose repeat test values are not clinically significant, currently taking corticosteroid or anti-inflammatory medications.
Outcome results
None listed