Bioelectrical Impedance Analysis Scales for the Measurement of Body Composition in Research Environments and in the Real World: Can They Be Used Reliably?

Intermittent energy restriction has become a popular method for the management of obesity. It is however a very old concept, although not always used specifically for weight loss, a good example being the Ramadan fast. While the Ramadan fast has been shown to lead to weight loss, the assessment of body composition changes may be another important consideration. Chapter 2 therefore assesses the effect of the Ramadan fast on body composition via a systematic review and meta-analysis. This showed that the Ramadan fast caused a decrease in all parameters of body composition. Subgroup analyses showed a significant decrease in fat percentage only in people with overweight or obesity. In studies used for the above review on the Ramadan fast, various methods are used to track body composition, a clear majority of them using bioelectrical impedance scales. These scales are commonly used due to them being a cheap, quick and easy method. Their ubiquitous use makes it important to understand their reliability. It has been suggested that rate of weight loss could possibly influence the utility of the scales. In Chapter 3, this was addressed by comparing the body composition measurements obtained by the scales to the 4-compartment model (a gold-standard for body composition measurement), both before and after a diet plan involving either FAST or SLOW weight loss for 16 weeks. We found that for individuals, the scales were generally inaccurate and imprecise, especially after weight loss (regardless of rate). In groups, the scales were much more reliable, with comparisons of the means and standard deviations of the scales versus the 4-compartment model showing no significant difference across all analyses. These results highlight that bioelectrical impedance scales may not be ideal for measuring body composition in individuals, although they may be suitable for use in groups, for instance, in the case of the Ramadan studies utilized in Chapter 2