Willemijn M. Vermeer

Portion size: review and framework for interventions

The prevalence of overweight and obesity has increased. A strong environmental factor contributing to the obesity epidemic is food portion size. This review of studies into the effects of portion size on energy intake shows that increased food portion sizes lead to increased energy intake levels. Important mechanisms explaining why larger portions are attractive and lead to higher intake levels are value for money and portion distortion. This review also shows that few intervention studies aiming to reverse the negative influence of portion size have been conducted thus far, and the ones that have been conducted show mixed effects. More intervention studies targeted at portion size are urgently needed. Opportunities for further interventions are identified and a framework for portion size interventions is proposed. Opportunities for intervention include those targeted at the individual as well as those targeted at the physical, economic, political and socio-cultural environment.

Small portion sizes in worksite cafeterias: do they help consumers to reduce their food intake?

Background:Environmental interventions directed at portion size might help consumers to reduce their food intake.Objective:To assess whether offering a smaller hot meal, in addition to the existing size, stimulates people to replace their large meal with a smaller meal.Design:Longitudinal randomized controlled trial assessing the impact of introducing small portion sizes and pricing strategies on consumer choices.Setting/participants:In all, 25 worksite cafeterias and a panel consisting of 308 consumers (mean age=39.18 years, 50% women).Intervention:A small portion size of hot meals was offered in addition to the existing size. The meals were either proportionally priced (that is, the price per gram was comparable regardless of the size) or value size pricing was employed.Main outcome measures:Daily sales of small and the total number of meals, consumers’ self-reported compensation behavior and frequency of purchasing small meals.Results:The ratio of small meals sales in relation to large meals sales was 10.2%. No effect of proportional pricing was found B=−0.11 (0.33), P=0.74, confidence interval (CI): −0.76 to 0.54). The consumer data indicated that 19.5% of the participants who had selected a small meal often-to-always purchased more products than usual in the worksite cafeteria. Small meal purchases were negatively related to being male (B=−0.85 (0.20), P=0.00, CI: −1.24 to −0.46, n=178).Conclusion:When offering a small meal in addition to the existing size, a percentage of consumers that is considered reasonable were inclined to replace the large meal with the small meal. Proportional prices did not have an additional effect. The possible occurrence of compensation behavior is an issue that merits further attention.

Equity-specific effects of 26 Dutch obesity-related lifestyle interventions

CONTEXT Reducing health inequalities is a policy priority in many developed countries. Little is known about effective strategies to reduce inequalities in obesity and its underlying behaviors. The goal of the study was to investigate differential effectiveness of interventions aimed at obesity prevention, the promotion of physical activity or a healthy diet by SES. EVIDENCE ACQUISITION Subgroup analyses in 2010 and 2011 of 26 Dutch studies funded by The Netherlands Organization for Health Research and Development after 1990 (n=17) or identified by expert contact (n=9). Methodologic quality and differential effects were synthesized in harvest plots, subdivided by setting, age group, intensity, and time to follow-up. EVIDENCE SYNTHESIS Seven lifestyle interventions were rated more effective and four less effective in groups with high SES; for 15 studies no differential effects could be demonstrated. One study in the healthcare setting showed comparable effects in both socioeconomic groups. The only mass media campaign provided modest evidence for higher effectiveness among those with high SES. Individually tailored and workplace interventions were either more effective in higher-SES groups (n=4) or no differential effects were demonstrated (n=9). School-based studies (n=7) showed mixed results. Two of six community studies provided evidence for better effectiveness in lower-SES groups; none were more effective in higher-SES groups. One high-intensity community-based study provided best evidence for higher effectiveness in low-SES groups. CONCLUSIONS Although for the majority of interventions aimed at obesity prevention, the promotion of physical activity, or a healthy diet, no differential effectiveness could be demonstrated, interventions may widen as well as reduce socioeconomic inequalities in these outcomes. Equity-specific subgroup analyses contribute to needed knowledge about what may work to reduce socioeconomic inequalities in obesity and underlying health behaviors.

From the point-of-purchase perspective: A qualitative study of the feasibility of interventions aimed at portion-size

OBJECTIVES Food portion-sizes might be a promising starting point for interventions targeting obesity. The purpose of this qualitative study was to assess how representatives of point-of-purchase settings perceived the feasibility of interventions aimed at portion-size. METHODS Semi-structured interviews were conducted with 22 representatives of various point-of-purchase settings. Constructs derived from the diffusion of innovations theory were incorporated into the interview guide. Each interview was recorded and transcribed verbatim. Data were coded and analysed with Atlas.ti 5.2 using the framework approach. RESULTS According to the participants, offering a larger variety of portion-sizes had the most relative advantages, and reducing portions was the most disadvantageous. The participants also considered portion-size reduction and linear pricing of portion-sizes to be risky. Lastly, a larger variety of portion-sizes, pricing strategies and portion-size labelling were seen as the most complex interventions. In general, participants considered offering a larger variety of portion-sizes, portion-size labelling and, to a lesser extent, pricing strategies with respect to portion-sizes as most feasible to implement. CONCLUSIONS Interventions aimed at portion-size were seen as innovative by most participants. Developing adequate communication strategies about portion-size interventions with both decision-makers in point-of-purchase settings and the general public is crucial for successful implementation.

Small, medium, large or supersize? The development and evaluation of interventions targeted at portion size

In the past decades, portion sizes of high-caloric foods and drinks have increased and can be considered an important environmental obesogenic factor. This paper describes a research project in which the feasibility and effectiveness of environmental interventions targeted at portion size was evaluated. The studies that we conducted revealed that portion size labeling, offering a larger variety of portion sizes, and proportional pricing (that is, a comparable price per unit regardless of the size) were considered feasible to implement according to both consumers and point-of-purchase representatives. Studies into the effectiveness of these interventions demonstrated that the impact of portion size labeling on the (intended) consumption of soft drinks was, at most, modest. Furthermore, the introduction of smaller portion sizes of hot meals in worksite cafeterias in addition to the existing size stimulated a moderate number of consumers to replace their large meals by a small meal. Elaborating on these findings, we advocate further research into communication and marketing strategies related to portion size interventions; the development of environmental portion size interventions as well as educational interventions that improve people’s ability to deal with a ‘super-sized’ environment; the implementation of regulation with respect to portion size labeling, and the use of nudges to stimulate consumers to select healthier portion sizes.

Two pack king size chocolate bars. Can we manage our consumption

This questionnaire study assessed peoples consumption intentions regarding two pack king size chocolate bars. Results showed that 92.9% of the respondents (n=143) intended to finish the chocolate bar within 1 day. The most important purchase considerations were hunger and not having considered the size. Furthermore, dietary restraint reduced the odds of a respondent intending to finish the two pack king size chocolate bar within 1 day. Based on the results, the availability and visibility of regular chocolate bars and healthier snacks should be increased, and consumers should be educated about the impact of portion sizes of high caloric snacks.

The process evaluation of two interventions aimed at portion size in worksite cafeterias.

BACKGROUND   In a previous study, the effectiveness of introducing a small meal in addition to the existing size and a proportional pricing strategy have been assessed in Dutch worksite cafeterias. To assess the degree of implementation and to inform the design of future interventions, the present study aimed to describe the process evaluation of both interventions. METHODS   Process evaluation components from Baranowski and Stables, and Rogers (i.e. Recruitment, Maintenance, Context, Resources, Implementation, Exposure, Contamination, and Continued use) were chosen as a theoretical basis. The process evaluation involved qualitative (e.g. structured observations, semi-structured interviews) and quantitative data (e.g. consumer questionnaires) collected from 17 intervention and eight control worksite cafeterias. RESULTS   In all intervention cafeterias, two portion sizes were offered. The pricing instructions were followed in 13 intervention cafeterias. The cafeterias managers indicated that they did not consider offering large and small meals as being complex, risky or time-consuming to implement. Some managers perceived the consumer demand as high, others as (too) low. One year after the study had ended, nine of the intervention cafeterias had continued (at least partly) to follow the protocol. CONCLUSIONS   Offering a smaller portion size in addition to the existing size, as well as proportional pricing, was generally implemented as prescribed by the protocol and can be considered promising in terms of continued use. However, additional efforts are needed to make the intervention more effective in motivating consumers to replace their large portion with a small portion.