The use of visual analogue scales to assess motivation to eat in human subjects: a review of their reliability and validity with an evaluation of newhand-held computerized systems for temporal tracking of appetite ratings

This present paper reviews the reliability and validity of visual analogue scales (VAS) in terms of (1) their ability to predict feeding behaviour, (2 ) their sensitivity to experimental manipulations, and (3) their reproducib ility. VAS correlate with, but do not reliably predict, energy intake to th e extent that they could be used as a proxy of energy intake. They do predi ct meal initiation in subjects eating their normal diets in their normal en vironment. Under laboratory conditions, subjectively rated motivation to ea t using VAS is sensitive to experimental manipulations and has been found t o be reproducible in relation to those experimental regimens. Other work ha s found them not to be reproducible in relation to repeated protocols. On b alance, it would appear, in as much as it is possible to quantify, that VAS exhibit a good degree of within-subject reliability and validity in that t hey predict with reasonable certainty, meal initiation and amount eaten, an d are sensitive to experimental manipulations. This reliability and validit y appears more pronounced under the controlled (but more artificial) condit ions of the laboratory where the signal : noise ratio in experiments appear s to be elevated relative to real life. It appears that VAS are best used i n within-subject, repeated-measures designs where the effect of different t reatments can be compared under similar circumstances. They are best used i n conjunction with other measures (e.g. feeding behaviour, changes in plasm a metabolites) rather than as proxies for these variables. New hand-held el ectronic appetite rating systems (EARS) have been developed to increase rel iability of data capture and decrease investigator workload. Recent studies have compared these with traditional pen and paper (P&P) VAS. The EARS hav e been found to be sensitive to experimental manipulations and reproducible relative to P&P. However, subjects appear to exhibit a significantly more constrained use of the scale when using the EARS relative to the P&P. For t his reason it is recommended that the two techniques are not used interchan geably.