The development of novel tools for the assessment of UK firefighter nutritional status for use in a multi-component worksite nutrition intervention programme

Lessons, Greg Richard (2021) The development of novel tools for the assessment of UK firefighter nutritional status for use in a multi-component worksite nutrition intervention programme. Doctoral thesis, London Metropolitan University.


Firefighters are at elevated risk of cardiovascular disease and myocardial infarction. Overweight and obesity prevalence in this occupational group may be greater than in the general population. This is the first nutrition-based study for UK firefighters, involving 28 fire stations and 575 firefighters based in London. This study was designed to develop population specific tools: body composition reference charts, a validated food frequency questionnaire (FFQ) and a cookery book for use in a multicomponent worksite intervention.

The validity of BMI for classification of firefighter adiposity status was investigated. Combined prevalence of male firefighter (n=497) overweight and obesity by BMI was 80%, which contrasted widely with the adiposity indices: percentage body fat (BF%) (63%), waist circumference (WC) (43%) and waist-to-height-ratio (WHtR) (59%). Female firefighters (n=78) exhibited lower combined prevalence of overweight and obesity compared to the male firefighters: BMI (43%), BF% (18%), WC (36%) and WHtR (27%). However, misclassification caused by BMI was widespread for both sexes, showing BMI’s specificity to be particularly poor, leading to high rates of false positives. This represents the first study to assess the adiposity of UK female firefighters and the first to comprehensively identify BMI to generate widespread misclassification of UK firefighters. Following this, a novel body composition reference system for UK firefighters was developed. This took the form of centile reference curves illustrating age-related changes in fat mass and skeletal muscle mass of firefighters, offering an improvement upon the limitations of BMI and BF%. Overweight and obesity cut-offs were defined at the 85th and 95th centiles which were chosen due to relative suitability and good agreement (97%; Kappa 0.86, p< 0.001) between the BF% reference curves and the fat-mass index reference curves at these centiles.

A novel FFQ was developed via population specific modification of the EPIC-Norfolk FFQ and validated against three 24hr recalls. Correlations between the methods were significant (p< 0.01) for energy (r=0.42), carbohydrate (r=0.42), protein (r=0.42), fat (r=0.35), fibre (r=0.34), saturated fatty acids (r=0.36), monounsaturated fatty acids (r=0.32), polyunsaturated fatty acids (r=0.24, p=0.05), vitamin C (r=0.26), calcium (r=0.45), iron (r=0.38) and sodium (r=0.32). Bland-Altman (BA) analyses indicated good agreement between methods for energy and each nutrient, with an average of 96% of cases falling between the limits of agreement. Cross-quartile analysis identified a low mean rate of misclassification (4.2%). In terms of reproducibility, the mean correlation between repeat administrations was 0.7 (p< 0.01), with >95% of cases falling between the BA limits of agreement. This constitutes the first FFQ validated for UK firefighters.

A worksite cookery workshop intervention and accompanying cookery book were developed and tested, demonstrating practical methods of healthy meal preparation along with environmental modification suggestions designed to ameliorate the established obesogenic food environment. This resulted in several key significant (p< 0.01) improvements to the mess, including 8 firefighting watches reinstating smaller plates, 10 watches leaving leftovers in the kitchen, 11 watches incorporating wholegrain products and 8 watches switching to making sauces/soups from scratch. Finally, the efficacy of a fire station-based nutrition intervention was tested in a cluster-controlled trial. This encompassed group education on non-communicable disease risk factors and the health benefits of adopting a Mediterranean diet. Dietary assessment was undertaken utilising the newly developed FFQ, which informed personalised nutrition consultation for each participant. Mixed design ANOVAS demonstrated significant improvements at 4-months post-intervention (p< 0.01) in daily mean intakes of energy (-244 kcal), total fat (-12 g), saturated fatty acids (-5g), sodium (-311 mg), sugars, preserves and snacks (-19 g). This contributed to concomitant mean body composition improvements in fat mass (-2 kg), BF% (-1.7%), WC (-1.7 cm), weight (-1.7 kg), BMI (-0.5 kg/m2), mood (+0.9) and energy level (+1.2) compared with the control group increasing in WC (+1.9 cm).

In conclusion, the population specific tools can be utilised in a worksite intervention which led to improvements in nutrient intake and body composition. The external validity of the tools, along with the intervention’s high level of feasibility further renders it suitable for rollout on a national level.

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