Cardiovascular disease risk factors, chrononutrition and the feasibility of time restricted eating for UK firefighters

Abstract

This thesis investigated the prevalence of cardiovascular disease (CVD) risk factors among firefighters, assessed their chrononutrition behaviours between working and non-working days, and examined if these behaviours contribute to CVD risk. Then, the feasibility of a chrononutrition based intervention, time restricted eating (TRE), was assessed with the aim to improve body composition and reduce CVD risk factors among firefighters. Study 1 conducted a systematic review and meta-analyses of 25 studies, which aimed to provide a global insight into the prevalence of the metabolic syndrome (MetSyn), its components, and body mass index (BMI) defined overweight and obesity among firefighters. In total 22.3% of firefighters had MetSyn, with hypertension (39.2%), abdominal obesity (37.9%), hypertriglyceridemia (30.2%), dyslipidaemia (30.1%), and hyperglycaemia (21.1%) all prevalent. Overweight and obesity prevalence rates were 44.1% and 35.6% respectively, with MetSyn prevalence increasing by 5% with each unit increase in BMI. The systematic review revealed a lack of literature exploring the prevalence of MetSyn in UK firefighters and underlying behavioural factors that may promote CVD risk. Study 2 assessed chrononutrition behaviours working and non-working days, and the differences in these behaviours between self-reported BMI classifications amongst 164 UK firefighters. The online survey revealed that 48.2% and 23.2% were overweight and obese, respectively. During work days, firefighters' wake time and the timing of their first eating event (FEV) were significantly earlier, which resulted in a significantlylonger eating window (EW), compared to non-working days. Firefighters categorised as obese had significantly longer daily EWs, skipped breakfast and had nighttime snacks on significantly more occasions per week compared to their healthy weightcolleagues. Study 3 measured the prevalence of MetSyn components, alongside the chrononutrition behaviours of 92 UK firefighters. MetSyn prevalence was 7.6%, with hypertension (44.6%), dyslipidaemia (20.7%), hypertriglyceridaemia (12.0%),abdominal obesity (10.9%), and hyperglycaemia (6.5%) varying in prevalence. Significant correlations were found between delays in last eating event (LEV) and extended EW with increased waist circumference (WC) and diastolic blood pressure (DBP) during non-working days. Delays in FEV was significantly correlated with increased fasting blood glucose (FBG) on working days. A TRE acceptability questionnaire revealed that prescribing a 10 h EW, self-selecting the timing of the EW and allowing black tea/coffee during the fasting period would support adherence to the TRE intervention in study 4. Study 4 evaluated the feasibility of a 4-week, 10 h TRE intervention and changes in CVD risk factors and body composition among 24 UK firefighters. After a 2-weekbaseline period, the TRE group followed a self-selected 10-hour EW for 4 weeks on non-working days, whilst the control (CON) group maintained usual eating patterns. Firefighters completed TRE around 5 d.week (79.2%) for the duration of the TREintervention, which resulted in significant reductions (p < 0.05) in body mass, BMI, BF%, WC, BP, and FBG. Mainly positive effects of TRE on biological, psychological, and social factors were reported in the diet satisfaction questionnaire. Overall, this thesis found that overweight/obesity and CVD risks are prevalent among firefighters, with poorer chrononutrition behaviours likely contributing to these risks. The 4-week ~10 h TRE intervention was feasible and effective in reducing body mass and improving cardiovascular health. Future research should assess how 1) TRE affects energy balance and dietary quality in firefighters and 2) explore the feasibility of TRE across different duty systems.

Date of Award	4 Oct 2024
Original language	English
Awarding Institution	University of Bedfordshire
Supervisor	Jeffrey Aldous (Supervisor), Angel Chater (Second supervisor) & Louise Ferrandino (Third supervisor)