A quantitative analysis of the relationship between habitual energy expenditure, fitness and the metabolic cardiovascular syndrome

• Published in: British journal of nutrition 1998-09, Vol.80 (3), p.235-241
• Main Authors: Wareham, Nicholas J., Hennings, Susie J., Byrne, Christopher D., Hales, C. Nicholas, Prentice, Andrew M., Day, Nicholas E.
• Format: Article
• Language: English
• Subjects: Adult; Analysis. Health state; Anthropometry; Biological and medical sciences; Body Mass Index; Cholesterol, HDL - blood; Cohort Studies; Energy expenditure; Energy Metabolism - physiology; Epidemiology; Female; Fitness; General aspects; Glucose Intolerance - metabolism; Heart Rate; Humans; Hypertension - metabolism; Hypertriglyceridemia - metabolism; Male; Medical sciences; Metabolic cardiovascular syndrome; Odds Ratio; Oxygen Consumption; Physical activity; Physical Fitness - physiology; Public health. Hygiene; Public health. Hygiene-occupational medicine; Reproducibility of Results; Syndrome
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1017/S0007114598001287

Previous epidemiological studies have suggested an association between low levels of physical activity, fitness and the metabolic cardiovascular syndrome. However, many studies have used subjective non-quantitative questionnaire-based methods for assessing physical activity which do not distinguish between the different dimensions of this complex exposure, and in which measurement error in the exposure has not been estimated. These deficiencies in the measurement of this exposure complicate the interpretation of the results of epidemiological studies, and consequently make it difficult to design appropriate interventions and to estimate the expected benefit which would result from intervention. In particular, it is unclear whether public health advice should be to increase total energy expenditure, or to attempt to raise fitness by recommending periods of vigorous activity. To separate the effects of fitness and total energy expenditure in the aetiology of the metabolic cardiovascular syndrome, we measured the physical activity level (PAL), defined as total energy expenditure: BMR, and fitness (maximum O2 consumption (Vo2max per kg), measured in a sub-maximal test) in a cross-sectional population-based study of 162 adults aged 30–40 years. Heart-rate monitoring with individual calibration was used to measure total energy expenditure using the HRFlex method (Ceesay et al. 1989) which has been validated previously against doubly-labelled water and whole-body calorimetry. The relationship between a single measure of PAL, Vo2max per kg and the usual or habitual level for each exposure was measured in a sub-study of twenty-two subjects who undertook four repeated measures over the course of 1 year. This study design allows the reliability coefficient to be computed, which is used to adjust the observed associations for measurement error in the exposure. Twelve men (16.4%) and sixteen women (18.0%) were defined as having one or more features of the metabolic cardiovascular syndrome. The univariate odds ratio for each increasing quartile for PAL was 0.64 (95 % CI 0.43–0.94) and was 0.49 (95 % CI 0.32–0.74) for Vo2max per kg, suggesting that the association with the metabolic cardiovascular syndrome was stronger for fitness than for PAL. However, after adjustment for obesity and sex, and correction for exposure measurement error, the odds ratio per quartile for PAL was 0.32 (95 % CI 0.13–0.83) and 0.44 (95 % CI 0.24–0.78) for Vo2max per kg. Thus, although univaria