Metabolic health effects of the timing of lifestyle behaviours in a combined lifestyle intervention in adults who have obesity or are overweight with complications

BACKGROUND: As done in combined lifestyle interventions (CLI), a combination of physical activity, diet, and sleep interventions is effective in reducing body mass index (BMI) and hyperglycaemia. The timing of the behaviours during the day may also affect metabolic health, due to individuals' circadian rhythms, but the impact of this is not well known. Thus, the inclusion of education on the timing of lifestyle behaviours may be an important addition to CLIs. Therefore, we aim to investigate the metabolic health effect of adding education on timing of lifestyle behaviours to an online CLI among adults who have obesity or are overweight with complications, compared to standard CLI, and routine care.

METHODS: In this two-armed, cluster-randomized, superiority, pragmatic trial, at least ten CLI counselling groups will be cluster-randomized to either the standard CLI or the TIMED CLI, with added education on the timing of sleep, physical activity, and dietary intake. Among these clusters, we aim to recruit approximately 100 participants. The primary outcome is self-reported BMI at baseline, and at 3, 9, and 24 months. Secondary outcomes are health-related quality of life (HRQoL) measured using a questionnaire, self-reported waist circumference, fasting glucose and HbA1c measured using at-home finger prick testing at baseline, and at 3, and 9 months. Adherence will be assessed through questionnaires and attendance to the CLI sessions. In addition, an observational control group of 800 participants from a routine care database will be included for comparison. Recruitment started in July 2024.

DISCUSSION: To our knowledge, this is the first pragmatic, cluster-randomized trial that investigates the incorporation of education on circadian timing of lifestyle behaviours in a routine care CLI. The pragmatic design will enable the investigation of the feasibility and metabolic health effect of implementing these timed interventions in a routine care setting.

TRIAL REGISTRATION: ISRCTN registry, protocol number ISRCTN14642827. Registered on 7 December 2023, www.isrctn.com/ISRCTN14642827.