David Marchiori

Container size influences snack food intake independently of portion size

While larger containers have been found to increase food intake, it is unclear whether this effect is driven by container size, portion size, or their combination, as these variables are usually confounded. The study was advertised as examining the effects of snack food consumption on information processing and participants were served M&Ms for free consumption in individual cubicles while watching a TV show. Participants were served (1) a medium portion of M&Ms in a small (n=30) or (2) in a large container (n=29), or (3) a large portion in a large container (n=29). The larger container increased intake by 129% (199 kcal) despite holding portion size constant, while controlling for different confounding variables. This research suggests that larger containers stimulate food intake over and above their impact on portion size.

Is It Better to Think Unconsciously or to Trust Your First Impression?: A Reassessment of Unconscious Thought Theory

According to unconscious thought theory, complex decisions are best made after a period of distraction assumed to elicit “unconscious thought.” Here, the authors suggest instead that the superiority of decisions made after distraction results from the fact that conscious deliberation can deteriorate impressions formed on-line during information acquisition. The authors found that participants instructed to form an impression made better decisions after distraction than after deliberation, thereby replicating earlier findings. However, decisions made immediately were just as good as decisions made after distraction, which suggests (a) that people had already made their decision during information acquisition, (b) that deliberation without attention does not occur during distraction, and (c) that ruminating about ones first impression can deteriorate decision quality. Strikingly, in another condition that should have favored unconscious thought even more, deliberated decisions were better than immediate or distracted decisions. These findings were replicated in a field study.

The portion size effect on food intake. An anchoring and adjustment process

People consistently over-eat when served a large compared with a small (appropriate) portion of food. However, the mechanism underlying this so-called portion size effect is not well understood. We argue that the process of anchoring and adjustment naturally describes this effect, such that the size of a presented portion works as an anchor that strongly influences consumption. The classical anchoring and adjustment paradigm was applied to six hypothetical eating situations. Participants were asked to imagine being served either a small or a large portion of food (i.e., low and high anchor) and to indicate whether they would consume more or less than this amount. Then, they indicated how much they would eat. These estimates were compared with a no-anchor condition where participants did not imagine a specific portion size but only indicated how much they would eat. In addition, half of participants in the anchoring conditions received a discounting instruction stating that the portion size they had been asked to imagine was randomly selected and thus not informative for their consumption estimate. As expected, participants who imagined to be served larger portions estimated to consume significantly more food than participants in the no-anchor condition, and participants who imagined to be served smaller portions estimated to consume significantly less food than participants in the no-anchor condition. The discounting manipulation did not reduce this effect of the anchors. We suggest that the process of anchoring and adjustment may provide a useful framework to understand the portion size effect and we discuss implications of this perspective.

Smaller Food Item Sizes of Snack Foods Influence Reduced Portions and Caloric Intake in Young Adults

Studies considering the impact of food-size variations on consumption have predominantly focused on portion size, whereas very little research has investigated variations in food-item size, especially at snacking occasions, and results have been contradictory. This study evaluated the effect of altering the size of food items (ie, small vs large candies) of equal-size food portions on short-term energy intake while snacking. The study used a between-subjects design (n=33) in a randomized experiment conducted in spring 2008. In a psychology laboratory (separate cubicles), participants (undergraduate psychology students, 29 of 33 female, mean age 20.3±2 years, mean body mass index 21.7±3.7) were offered unlimited consumption of candies while participating in an unrelated computerized experiment. For half of the subjects, items were cut in two to make the small food-item size. Food intake (weight in grams, kilocalories, and number of food items) was examined using analysis of variance. Results showed that decreasing the item size of candies led participants to decrease by half their gram weight intake, resulting in an energy intake decrease of 60 kcal compared to the other group. Appetite ratings and subject and food characteristics had no moderating effect. A cognitive bias could explain why people tend to consider that one unit of food (eg, 10 candies) is the appropriate amount to consume, regardless of the size of the food items in the unit. This study suggests a simple dietary strategy, decreasing food-item size without having to alter the portion size offered, may reduce energy intake at snacking occasions.

Split Them! Smaller Item Sizes of Cookies Lead to a Decrease in Energy Intake in Children

OBJECTIVE Examine the influence of altering the size of snack food (ie, small vs large cookies) on short-term energy intake. METHODS First- and sixth-graders (n = 77) participated in a between-subjects experimental design. All participants were offered the same gram weight of cookies during an afternoon tea at their school. For half of the participants, food was cut in 2 to make the small item size. Food intake (number of cookies, gram weight, and energy intake) was examined using ANOVA. RESULTS Decreasing the item size of food led to a decrease of 25% in gram weight intake, corresponding to 68 kcal. Appetitive ratings and subject and food characteristics had no moderating effect. CONCLUSIONS AND IMPLICATIONS Reducing the item size of food could prove a useful dietary prevention strategy based on decreased consumption, aimed at countering obesity-promoting eating behaviors favored by the easy availability of large food portions.

Preventing the pack size effect: Exploring the effectiveness of pictorial and non-pictorial serving size recommendations

People eat more from large than from small packs, which is known as the pack size effect. We hypothesized that providing a serving size recommendation would reduce the influence of the pack size on consumption and would thus diminish the pack size effect. Moreover, we hypothesized that a pictorial serving size recommendation, displaying food amounts visually, would be more effective than a non-pictorial recommendation that communicates the recommended amount in grams only. We tested these hypotheses in two online experiments (N = 317 and N = 324) and in one lab experiment (N = 89). In the online experiments, participants were shown a small or a large pack of unhealthy snacks, with or without a serving size recommendation. The main outcome measure was expected consumption. Replicating the pack size effect in an online setting, we found that participants expected to consume more food from large than from small packs. Furthermore, the pack size effect was considerably stronger for men than for women. Importantly, when including portion size preferences as a covariate, the pictorial serving size recommendation significantly reduced expected consumption, especially when placed on a large pack, as hypothesized. The non-pictorial serving size recommendation had no effect. In the lab experiment, students received a large bag of M&Ms which did or did not contain the pictorial serving size recommendation. We again included general portion size preferences as a covariate. The serving size recommendation significantly lowered the amount of M&Ms that participants served themselves, but only when participants reported to have noticed the serving size recommendation. We conclude that providing a pictorial serving size recommendation can be an effective intervention strategy to reduce the pack size effect, if it attracts sufficient attention.

Citizen approval of nudging interventions promoting healthy eating: the role of intrusiveness and trustworthiness

BackgroundNudging interventions have lately been widely adopted by policy makers to increase the welfare of society and to help citizens make better choices. Hence, it has become important to understand the conditions under which they are approved. While most research has looked into whether professionals approve of nudging interventions, surprisingly the opinion of the target group has been widely ignored. This study investigated citizens’ level of approval of nudging in the realm of healthy eating promotion, as well as its boundary conditions.MethodsParticipants (N = 1441) from the US and seven European countries were probed for their level of approval of nudges. Moreover, we investigated whether these levels of approval were dependent on the level of intrusiveness of the nudge and on the type and trustworthiness of the source (policy makers, experts, industry) implementing the nudge.ResultsPeople revealed moderate to high levels of approval with nudging across all countries. Intrusiveness and nudging approval were negatively associated. Nudges implemented by experts received more approval than those by policy makers. In general, approval increased with the trustworthiness of the source.ConclusionsThese results provide information for European and American policy makers considering using nudging in their policy repertoire.