The term hunger is used in more than one sense by both scientists and the lay public. World hunger is a widely used phrase to describe the shortage of food and state of malnutrition experienced by a substantial proportion of the world's population. Its use is emotive and largely descriptive. It is in the study of motivation that the term takes on a more precise and individual definition. In this context, hunger describes the drive or the motivational force that urges us to seek and consume food. It is the expression of a biological need to sustain growth and life. Hunger is therefore a purposeful experience that possesses a clear biological function.
There are two ways in which the term hunger is used within nutritional science. One is its use as a motivational construct in a scientific theory. Here, hunger is inferred from directly observable and measurable events. In this way, inferring increased or high levels of hunger from a long period of food deprivation or an increased willingness to expend effort in order to obtain food, hunger becomes a mediating concept or intervening variable. However, a more familiar use of the word is that collection of conscious feelings or sensations that are linked to a desire to obtain and eat food. This is the sense in which lay people understand the term hunger and is what researchers attempt to capture by means of rating scales and other measurement devices.
The first serious investigation of the everyday experience of hunger used a questionnaire in which people were asked to note the presence of physical sensations in a number of bodily areas, together with moods, urges to eat, and preoccupation with thoughts of food. It was found that the observation, 'I feel hungry,' is typically based on the perception of bodily feelings, which at times are very strong. Gastric sensations, a hollow feeling or stomach rumbling, are frequent indicators of hunger, although people also report sensations in the mouth, throat, and head. These accompany more diffuse feelings of restlessness and excitability as well as an urge to eat. The consumption of food changes both the pattern of physical sensations and the accompanying emotional feelings, with unpleasant and aversive sensations becoming replaced by more pleasant ones. So, for example, an aching stomach becomes relaxed and the feeling of excitement and irritability is replaced by one of contentment.
Subsequent research has confirmed these general patterns of characteristic premeal sensations and feelings, particularly with regard to the salience of gastric sensations. However, it has also noted a great deal of variability both within and between individuals. In other words, hunger demands neither the consistent presence of single sensations prior to every act of eating nor in every person sitting down to eat. Despite this variability people are able to, and frequently do, make judgments regarding their state of hunger, partly through reference to these sensations.
in accord, the subjective report and inferred construct can as easily diverge.
The two most common methods for quantifying hunger are fixed-point rating scales and visual analog scales (Figure 1). Fixed-point scales are quick and simple to use, and the data they provide are easy to analyze. Past examples of these scales show they vary greatly in complexity. In considering the appropriate number of points to be included in this type of scale, the freedom to make a range of possible responses must be balanced against the precision and reliability of the device. Research seems to indicate that scales with an insufficient number of fixed points can be insensitive to subtle changes in subjective experience. In addition, the fixed points are important determinants of the way people use the scales and distribute their ratings.
One way of overcoming some of these failings is to abolish the points completely. Thus, visual analog scales are horizontal lines (often 100 or 150 mm long), unbroken and unmarked except for word anchors at each end. The user of the scale is instructed to mark the line at the point that most accurately reflects the intensity of the subjective feeling at that time. The researcher measures the distance to that mark in millimeters from the negative end (no hunger), thus yielding a score of 0-100 (or 150). This is done either by hand or automatically if presented by computer screen. By doing away with all of the verbal labels except the end definitions, visual analog scales retain the advantages of fixed-point scales, while avoiding many of the problems with uneven response distributions.
An important aspect of these methods concerns the interpretation of differences between the fixed points or intervals on a visual analog scale. So, for example, it should not be assumed that the difference between 20 and 30 mm on a hunger scale is
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