Review
Liking vs. wanting food: Importance for human appetite control and weight regulation

https://doi.org/10.1016/j.neubiorev.2007.03.004Get rights and content

Abstract

Current train of thought in appetite research is favouring an interest in non-homeostatic or hedonic (reward) mechanisms in relation to overconsumption and energy balance. This tendency is supported by advances in neurobiology that precede the emergence of a new conceptual approach to reward where affect and motivation (liking and wanting) can be seen as the major force in guiding human eating behaviour. In this review, current progress in applying processes of liking and wanting to the study of human appetite are examined by discussing the following issues: How can these concepts be operationalised for use in human research to reflect the neural mechanisms by which they may be influenced? Do liking and wanting operate independently to produce functionally significant changes in behaviour? Can liking and wanting be truly experimentally separated or will an expression of one inevitably contain elements of the other? The review contains a re-examination of selected human appetite research before exploring more recent methodological approaches to the study of liking and wanting in appetite control. In addition, some theoretical developments are described in four diverse models that may enhance current understanding of the role of these processes in guiding ingestive behaviour. Finally, the implications of a dual process modulation of food reward for weight gain and obesity are discussed. The review concludes that processes of liking and wanting are likely to have independent roles in characterising susceptibility to weight gain. Further research into the dissociation of liking and wanting through implicit and explicit levels of processing would help to disclose the relative importance of these components of reward for appetite control and weight regulation.

Introduction

According to the French National Nutrition-Health Program (2001–2005) it is essential that an individual's food choice remains a ‘free act’ and that eating is recognised as a moment of pure pleasure. In order to fully appreciate these premeditated episodes of sensuality, it is not sufficient to focus only on the hedonic sensations arising from events in the mouth. The joy of eating can be as much to do with the preparation and effort that one invests in their chosen food and of course the expectancy and anticipation that intensify then peak in the final moments before ingestion. In summary, the pleasure of food can be seen as an interaction of liking and wanting, and experiencing one without the other—although pleasurable in isolation—stops short of full reward.

Advances in neurobiology are helping to characterise the substrate mediating hedonic processes of consumption, and they are precipitating the emergence of a new conceptual approach to reward where affect and motivation (a.k.a. liking and wanting) can be seen as the major force in guiding human eating behaviour. This concept is especially important for the study of ingestive behaviour in the modern world, where food is plentiful, cheap, energy-dense, and enticing, and physical activity is being reduced to a luxury afforded by environment and lifestyle. We have reached an age where weight control has been turned upside down from an instinctual, highly regulated system, to a process requiring considerable cognitive effort (Peters et al., 2002). Furthermore, where overweight and obesity have taken hold, losing weight and defending that loss (especially in an environment where our hedonic drives are encouraged and exploited) can change from a daily struggle, to a losing battle (e.g. Ikeda et al., 2005).

Parsing reward from a unitary process into distinguishable liking and wanting components in neurobiological studies (Berridge and Robinson, 2003) has struck a chord that is resonating across many disciplines and in different areas of research. In the field of ingestive behaviour alone it has implications for characterising eating disorders and obesity, identifying pharmacological targets, the psychology of appetite control, phenotypic profiling of resistance and susceptibility to weight gain, and industrial product development. Despite the possibilities of a dual process modulation of food reward, several issues remain to be addressed: How can these concepts be operationalised for use in human appetite research? Can they be translated into observable entities that reflect the neural mechanisms by which they may be influenced? Do liking and wanting operate independently to produce functionally significant changes in behaviour? Can liking and wanting be truly separated or will an expression of one inevitably contain elements of the other? In this review, current progress in applying processes of liking and wanting to the study of human appetite and ingestive behaviour are examined and the importance of these concepts for human appetite research are discussed.

Section snippets

Neurobiological study of liking and wanting

Our capacities in neuroscience can reveal—to some extent—the circuits responsible for the reward we derive from food. The picture emerging is that food reward, rather than being a unitary neurological entity, is represented functionally and structurally by distinct components. One such distinction, between processes associated with affective vs. motivational consequences of ingesting food, has received much recent attention (Berridge, 1996). With principle focus on opioid neurotransmission in

From core processes to constructs in human appetite

If core processes of liking and wanting can independently modulate food reward both implicitly and explicitly, it is important to understand how they can be approached and rendered suitable for the study of ingestive behaviour in humans. Even to date, the role of food reward in human appetite behaviour is mostly treated as a single entity embodied by a ‘palatability’ or ‘pleasantness’ factor and its effects on appetite control (Yeomans, 1998). The logical view is that liking and wanting co-vary

Reward and appetite control: homeostatic and hedonic interplay

A key issue in the study of appetite control is the relationship between reward and homeostatic drives arising from biological needs (Yeomans et al., 2004a). Historically, hedonic processes have been viewed as a function of nutritional need-state. In a state of depletion, the hedonic response (experienced palatability) to energy providing foods is enhanced and when replete, the hedonic effect of these foods is reduced (Cabanac, 1989). This view is compatible with the link between energy density

Liking, wanting and ingestive behaviour: a re-examination of selected studies

Considering that most studies have repeatedly shown that palatability—a factor influencing the reward value of food—has an effect on intake, this would support the notion that reward plays a role in the process of satiation (De Graaf et al., 1999). However, it is uncertain how processes of liking and wanting might independently modulate the effect of reward on appetite to influence ingestive behaviour. With a dual process perspective on reward, it becomes possible to re-examine some of the

Dual-component contributions to the study of reward in human appetite

With a dual-process model of reward, retrospective evaluation of the literature may help to throw light on the relationship between food reward, appetite and ingestive behaviour. More recently, researchers are beginning to consider liking and wanting interpretations of their own study findings and some are specifically tuning their methodologies to allow for separations of motivation and affective responding to food. These studies provide examples of how liking and wanting may be operationally

Further conceptual development

Parsing reward into separable components provides a parsimonious theoretical framework within which to study ingestive behaviour. However, liking and wanting are not well understood constructs in human appetite. Berridge (1996) advocated a minimal definition of these processes, opting to focus instead on their role and function through expanding empirical study. However, as more investigations start to draw on dual component theories to tackle their research questions, and interpret their

Implication for weight gain and obesity

Thanks in part to a better understanding of the interaction of homeostatic and hedonic processes of appetite and the phenomenon of non-homeostatic consumption, reward is growing to be viewed as an significant risk factor in weight gain leading to obesity (Nasser, 2001; Yeomans et al., 2004a, Yeomans et al., 2004b; Blundell and Finlayson, 2004; Erlanson-Albertsson, 2005). But what is the evidence that reward may play a role in the aetiology of obesity? Some studies have implicated individual

Conclusion

Prompted by findings on the neural structure of food reward in the brain, it is possible to take a fresh look at the role of reward in human appetite and weight regulation. Research shows that hedonic processes interact with the homeostatic system of energy regulation, and that this can influence the organisation of ingestive behaviour, but less is understood about how liking and wanting components of reward might work together or separately to modulate appetite. An important consideration is

Postscript

It should not be forgotten that—strictly speaking—liking and wanting should be seen to have the logical status of theoretical constructs. Our preferred view is that liking and wanting should be viewed as intervening variables that help us to understand the role of hedonics in appetite control. Their existence should not be taken to mean that these processes are structurally embodied in a neural substrate. Rather, that different neurochemical pathways can separately influence the events that can

Acknowledgement

This research was supported by Medical Research Council (MRC) Case award G78/8223 in conjunction with NRC, Lausanne.

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