None listed
Conditions
Brief summary
For shift workers there is an increased risk of 23% of developing obesity and 44% of developing type 2 diabetes. There are currently 1.5 million Australians (~16% of workforce population) who are at risk. The risk of obesity and type 2 diabetes in this population group do not appear to be related solely to overall energy intake. Previous research has shown that meal timing i.e. eating late into the night, as is common among shift worker, is associated with metabolic complications such as impaired glucose tolerance and insulin resistance, potentially contributing to weight gain. However, there is currently a lack of evidence to identify effective weight loss strategies in shift workers with obesity. We aim to compare three weight loss regimens in a population of shift workers to identify weight loss strategies that will a) result in successful weight loss and b) be flexible to the demanding lifestyles of the shift working population. This six month dietary intervention study will compare continuous energy restriction (diet 1) with intermittent fasting (5:2). The two fast days will either be days that participants work a day shift (diet 2) or days that participants work night shift (diet 3). The study hypothesises that each of the dietary interventions will be effective at inducing weight loss but there will be a differential effect of the diets across time on HOMA-IR (a measure of insulin resistance).
Interventions
Diet 1: 5:2 Day fasting diet
For five days of the week participants will eat their habitual diet, and on two days of the week (the two ‘fast’ days) they will be required to restrict their energy intake to 2100 kJ/day (female) or 2500 kj (male). These two days will correspond with days that incorporate a day shift. Participants will be provided with study food on each of the energy restriction days.
Diet 2: 5:2 Night fasting diet
For five days of the week participants will eat their usual diet,
Diet 1: 5:2 Day fasting diet For five days of the week participants will eat their habitual diet, and on two days of the week (the two ‘fast’ days) they will be required to restrict their energy intake to 2100 kJ/day (female) or 2500 kj (male). These two days will correspond with days that incorporate a day shift. Participants will be provided with study food on each of the energy restriction days. Diet 2: 5:2 Night fasting diet For five days of the week participants will eat their usual diet, and on two days of the week (the two ‘fast’ days) they will be required to restrict their energy intake to approximately 2100 kJ/day (female) or 2500 kJ (male). These two days will correspond with days that incorporate a night shift. Participants will be provided with study food on each of the energy restriction days. Diet 3: 20% Continuous daily Energy Restriction (20% ER) Based on a participant’s habitual diet (recorded at baseline), usual intake of total energy (kJ) will be reduced by 20%. Participants will be provided with study meals on two days of the week so that the same level of support is provided to each of the three intervention groups. Each dietary strategy (5:2 Day; 5:2 Night; 20% CER) will be followed for 6 months. Dietitians will deliver the intervention to each individual in person. Following their baseline visit, participants will meet with a dietitian in person every 2 weeks for the first two months (4 visits), and then monthly (4 visits). Following the intervention period, there will be a 12 month maintenance phase during which time participants will be monitored. During the 12 month maintenance phase, participants will receive a phone call from a study dietitian one month into the maintenance phase, and then meet the study dietitian in person at 2 months, 6 months and then at 12 months. Adherence to dietary interventions will be monitored and assessed through a combination of food diaries, 24 hr diet recalls and checklists.
Sponsors
A/Professor Maxine Bonham
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Prevention
Masking
Blinded (masking used) (Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
25 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
For Caucasian, BMI greater than or equal to 28 kg/m2 For Asians, BMI greater than or equal to 26 kg/m2 Weight loss in the past 3 months with weight change of no more than 5kg
Exclusion criteria
• Within healthy weight range • Individuals that do not work night shift i.e., day shift only workers are excluded • Have a genetic condition that impacts weight, appetite and/or metabolic measures (e.g., Prada Willi) • Diagnosed with a medical condition (e.g., Inflammatory bowel disease, Diabetes, Polycystic Ovarian Syndrome, CVD) • Pregnancy / breastfeeding • Dietary allergies / intolerance preventing consumption of provided study-meals • Prescription medication and over-the-counter-medication that affect metabolic outcomes/measures • Require drug-therapy (e.g., Insulin, Levothyroxine, anti-depressants, statins) that impacts weight, appetite and or metabolic measures. Assess on a case-by-case basis. • Failure to satisfy the investigator regarding suitability to participate for any other reason • Had previous weight loss surgery • Unwilling or unable to provide informed consent • Pregnant, planning a pregnancy or breastfeeding, and not prepared to do a pregnancy test • Not able to complete a 6-month weight loss intervention and a 12-month maintenance follow-up • Dietary allergies or dietary restrictions that prevent consumption of provided study foods • Taking extended leave from work in the next 6 months
Outcome results
None listed