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.

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.