Behaviour and Health Research Unit, Institute of Public Health, University of Cambridge, Cambridge, UK.
Oxford University Hospitals NHS Foundation Trust, The John Radcliffe Hospital, Oxford, UK.
Int J Behav Nutr Phys Act. 2019 Nov 27;16(1):114. doi: 10.1186/s12966-019-0883-5.
Altering the availability of healthier or less-healthy products may increase healthier purchases, but evidence is currently limited. The current study aimed to investigate the impact of altering the absolute-and-relative availability of healthier and less-healthy products - i.e. simultaneously altering the number of options available and the proportion of healthier options - in hospital vending machines.
An adapted multiple treatment reversal design was used, altering products available in ten vending machines serving snack foods and/or cold drinks in one English hospital. Machines were randomised to one of two sequences for the seven 4-week study periods: ABCADEA or ADEABCA. In Condition A (study periods 1, 4 and 7) the proportions of healthier products were standardised across all machines, so that 25% of all snack slots and 75% of drink slots were healthier. In Condition B, 20% of vending machine slots were emptied by removing less-healthy products. In Condition C, the empty slots created in Condition B were filled with healthier products. Conditions D and E were operationalised in the same way as B and C, except healthier products were removed in D, and then less-healthy products added in E. Sales data were obtained from machine restocking records. Separate linear mixed models were conducted to examine the impact of altering availability on energy purchased (kcal) from (i) snacks or (ii) drinks each week, with random effects for vending machine.
The energy purchased from drinks was reduced when the number of slots containing less-healthy drinks was decreased, compared to standardised levels (- 52.6%; 95%CI: - 69.3,-26.9). Findings were inconclusive for energy purchased from snacks when less-healthy snack slots were reduced (- 17.2%; 95%CI: - 47.4,30.5). Results for altering the number of slots for healthier drinks or snacks were similarly inconclusive, with no statistically significant impact on energy purchased.
Reducing the availability of less-healthy drinks could reduce the energy purchased from drinks in vending machines. Further studies are needed to establish whether any effects might be smaller for snacks, or found with higher baseline proportions of healthier options.
改变更健康或不太健康产品的供应情况可能会增加更健康产品的购买量，但目前证据有限。本研究旨在调查改变医院自动售货机中更健康和不太健康产品的绝对供应和相对供应的影响，即同时改变可提供的选项数量和更健康选项的比例。
采用改良的多次治疗逆转设计，改变一家英国医院的十台自动售货机中供应的零食和/或冷饮的产品。机器随机分配到两个序列中的一个，进行为期七周的四项研究：ABCDEA 或 ADEABCA。在条件 A（研究期 1、4 和 7）中，所有机器的健康产品比例标准化，即所有零食插槽的 25%和饮料插槽的 75%为更健康产品。在条件 B 中，通过去除不太健康的产品清空 20%的自动售货机插槽。在条件 C 中，在条件 B 中创建的空插槽中填充更健康的产品。条件 D 和 E 以与 B 和 C 相同的方式操作，只是在 D 中去除更健康的产品，然后在 E 中添加不太健康的产品。销售数据从机器补货记录中获得。单独的线性混合模型用于检查改变供应对每周购买的（i）零食或（ii）饮料中的能量的影响，其中自动售货机的随机效应。
与标准化水平相比，当减少含有不太健康饮料的插槽数量时，购买的饮料能量减少（-52.6%；95%CI：-69.3，-26.9）。当减少不太健康的零食插槽时，购买的零食能量减少（-17.2%；95%CI：-47.4，30.5），但结果不确定。改变更健康饮料或零食插槽数量的结果也不确定，对购买的能量没有统计学上的显著影响。
减少不太健康饮料的供应可能会减少自动售货机中饮料的购买能量。需要进一步研究，以确定对于零食，任何影响是否更小，或者在更健康的选择更高的基线比例下是否发现。
