(P15-004-23) Shifting Weight in Night Shift Workers: Results From a 24 Week, Parallel, Multi-Site, Randomised Controlled Trial (SWIFt)

Objectives: The lifestyle of shift workers is at odds with their daily circadian rhythms. Eating at night and sleeping during the day can cause weight gain, hyperglycemia and insulin resistance. Interventions to promote weight loss in shift workers need to consider timing of eating and fasting alongside energy restriction. This study evaluated three weight management programs designed for shift working populations. The lifestyle of shift workers is at odds with their daily circadian rhythms. Eating at night and sleeping during the day can cause weight gain, hyperglycemia and insulin resistance. Interventions to promote weight loss in shift workers need to consider timing of eating and fasting alongside energy restriction. This study evaluated three weight management programs designed for shift working populations.

Methods: A multi-site, parallel, randomized controlled trial was conducted to evaluate weight loss after participating in three 24-week weight-management programs. Night shift workers (25-65 years, BMI ≥ 28 kg/m² or 26 kg/m² (Asian)) working a minimum of two night shifts per week, with no presenting morbidities were randomized (n=250). Interventions followed were: continuous energy restriction (CER) or an isocaloric intermittent fasting strategy whereby the two fast days were either on day shift/days off (5:2 day) or whilst on night shift (5:2 night). The primary outcome was change in weight (kg). Secondary outcomes included changes in fasting glucose, lipids and body composition. We undertook a completers analysis.

Results: Of the 250 participants randomized, 24-week weight data is available for 170 participants. Preliminary data show significant weight loss was observed overall (p < 0.05) with 65% of participants losing ≥ 5% of their body weight. Blood glucose was lower (n = 145) after 24 weeks of weight loss (p < 0.05).

Conclusions: Clinically significant weight loss is achievable in night shift working populations after 24 weeks of energy restriction. An exploration of longer-term outcomes is important to ascertain weight loss maintenance.

Funding Sources: This project is funded by the National Health and Medical Research Council [APP1159762].