Food reward: Brain substrates of wanting and liking

The authors review the effect of the presence of others on food intake. In social facilitation studies, people tend to eat more in groups than when alone. In modeling studies, the presence of others may facilitate or inhibit intake, depending on how much these other people eat. Studies of impression management demonstrate that people tend to eat less in the presence of others than when alone. The authors attempt to reconcile these divergent literatures by reference to a model of inhibitory norms that govern eating. In the presence of palatable food, and in the absence of clear signals of satiety, people look outward to cues from the environment to determine when to stop eating. Socially derived inhibitory norms can account for either increased or decreased intake in the presence of others, depending on how much the others eat and the extent to which one is eager to impress them.

Effects of the presence of others on food intake: a normative interpretation

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 reproducibility. VAS correlate with, but do not reliably predict, energy intake to the extent that they could be used as a proxy of energy intake. They do predict meal initiation in subjects eating their normal diets in their normal environment. Under laboratory conditions, subjectively rated motivation to eat using VAS is sensitive to experimental manipulations and has been found to be reproducible in relation to those experimental regimens. Other work has found them not to be reproducible in relation to repeated protocols. On balance, 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 they predict with reasonable certainty, meal initiation and amount eaten, and are sensitive to experimental manipulations. This reliability and validity appears more pronounced under the controlled (but more artificial) conditions of the laboratory where the signal: noise ratio in experiments appears to be elevated relative to real life. It appears that VAS are best used in within-subject, repeated-measures designs where the effect of different treatments can be compared under similar circumstances. They are best used in conjunction with other measures (e.g. feeding behaviour, changes in plasma metabolites) rather than as proxies for these variables. New hand-held electronic appetite rating systems (EARS) have been developed to increase reliability of data capture and decrease investigator workload. Recent studies have compared these with traditional pen and paper (P&P) VAS. The EARS have 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 this reason it is recommended that the two techniques are not used interchangeably.

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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 new hand-held computerized systems for temporal tracking of appetite ratings.

During the last decades, eating out of home (OH) has gained importance in the diets worldwide. We document the nutritional characteristics of eating OH and its associations with energy intake, dietary quality and socioeconomic status. We carried out a systematic review of peer-reviewed studies in eight databases up to 10 March 2011. Of the 7,319 studies retrieved, 29 met the inclusion criteria and were analysed in this review. The quality of the data was assessed and a sensitivity analysis was conducted by isolating nationally representative or large cohort data from 6 and 11 countries, respectively. OH foods were important sources of energy in all age groups and their energy contribution increased in adolescents and young adults. Eating OH was associated with a higher total energy intake, energy contribution from fat in the daily diet and higher socioeconomic status. Two large studies showed how eating OH was also associated with a lower intake of micronutrients, particularly vitamin C, Ca and Fe. Although the studies were cross-sectional and heterogeneous in the way they classified eating OH, we conclude that eating OH is a risk factor for higher energy and fat intake and lower micronutrient intake.

D K Elmore

Papers

Social facilitation of the spontaneous meal size of humans occurs regardless of time, place, alcohol or snacks☆

Subjective hunger relationships with meal patterns in the spontaneous feeding behavior of humans: evidence for a causal connection