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NutrInsight • Satiety: from appetite sciences to food application
Two distinct components involved in the brain food reward
[Berridge et al., 1996; Berridge et al., 2003; Berridge, 2004]
The first hedonic/affective component (termed ‘liking’) is the result of a central process incorporating not only sensory properties but also the individual’s physiological state and associative history.
The second incentive salience/motivation component (termed ‘wanting’) refers to an underlying implicit and objective drive process and can be seen as the directed impulse or demand for a targeted food stimulus.
Finlayson et al. used computer-based paradigm to assess ‘liking’ (through pleasantness ratings) and ‘wanting’ (through forced-choice photographic procedure) [Finlayson et al., 2007a].
Explicit vs. Implicit Processes
Eating is an action open to awareness by the individual; however, it cannot be claimed that processes that control the expression of eating habits are necessarily conscious. Actually, introspective accounts of explicit processes are often subject to misinterpretation. A person may be aware of the act of eating per se whilst remaining unaware of the processes that determine the expression of appetite and the pattern of eating. For example, a person cannot be aware of the (implicit) changes in neuropeptides, hormones or other physiological processes that contribute to the initiation, termination and pattern of eating. Implicit measures of wanting might be more valuable assays of food motivation than explicit liking or wanting responses, as evidenced by VAS for example.
A study investigated the effect of satiation induced by savoury foods on implicit and explicit processes of liking and wanting by developing a computer-based procedure to measure them in hungry and satiated states [Finlayson et al., 2008]. Explicit measures were derived from VAS ratings whilst an implicit wanting measure was derived from reaction times in a forced-choice procedure. Satiation caused explicit ratings of liking and wanting to decrease for all food categories tested whereas implicit wanting increased for sweet categories but not for savoury. This work shows that implicit and explicit processes of food reward can be simultaneously measured and dissociated using a test meal.
These observations illustrate the important reciprocal relationships between hedonics and satiety. The rewarding aspects of food can interfere with satiety but, in return, satiety also modulates the hedonic responses (liking and wanting) to foods.
1.3 Manipulating satiation and satiety for appetite control
Satiation and satiety are inhibitory processes of food intake. Given the present epidemic of obesity and related metabolic disorders, it becomes interesting to see whether satiation and/or satiety could be manipulated in order to decrease food intake and potentially affect body weight control. Two strategies can be examined. First it might be possible to intensify satiation, in other words reduce the calories ingested at the time of meal, but maintain the strength of satiety. Alternatively, it might be possible to intensify satiety, in other words suppress hunger and reduce the calories consumed following the intake of a meal. In order to achieve this goal one food industry strategy is to modify properties of food that contribute most to satiety (energy, taste, nutritional composition for example).
The chapter 3 by Pr Marion Hetherington reviews the evidence presently available in this field. While strong evidence exists in favour of beneficial short-term effects of satiety enhancement on appetite and intake, longer-term effects on body weight control remain to be demonstrated.
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