Abstract: We included 24 studies, with the majority (20/24) giving concerns about risk of bias. All of the included studies investigated food products; none investigated alcohol or tobacco. The majority were conducted in laboratory settings (14/24), with adult participants (17/24), and used between-participants designs (19/24). All studies were conducted in high-income countries, predominantly in the USA (14/24). Six studies investigated availability interventions, of which two changed the absolute number of different options available, and four altered the relative proportion of less-healthy (to healthier) options. Most studies (4/6) manipulated snack foods or drinks. For selection outcomes, meta-analysis of three comparisons from three studies (n = 154) found that exposure to fewer options resulted in a large reduction in selection of the targeted food(s): SMD −1.13 (95% confidence interval (CI) −1.90 to −0.37) (low certainty evidence). For consumption outcomes, meta-analysis of three comparisons from two studies (n = 150) found that exposure to fewer options resulted in a moderate reduction in consumption of those foods, but with considerable uncertainty: SMD −0.55 (95% CI −1.27 to 0.18) (low certainty evidence). Eighteen studies investigated proximity interventions. Most (14/18) changed the distance at which a snack food or drink was placed from the participants, whilst four studies changed the order of meal components encountered along a line. For selection outcomes, only one study with one comparison (n = 41) was identified, which found that food placed farther away resulted in a moderate reduction in its selection: SMD −0.65 (95% CI −1.29 to −0.01) (very low certainty evidence). For consumption outcomes, meta-analysis of 15 comparisons from 12 studies (n = 1098) found that exposure to food placed farther away resulted in a moderate reduction in its consumption: SMD −0.60 (95% CI −0.84 to −0.36) (low certainty evidence). Meta-regression analyses indicated that this effect was greater: the farther away the product was placed; when only the targeted product(s) was available; when participants were of low deprivation status; and when the study was at high risk of bias. The current evidence suggests that changing the number of available food options or altering the positioning of foods could contribute to meaningful changes in behaviour, justifying policy actions to promote such changes within food environments. However, the certainty of this evidence as assessed by GRADE is low or very low. To enable more certain and generalisable conclusions about these potentially important effects, further research is warranted in real-world settings, intervening across a wider range of foods - as well as alcohol and tobacco products - and over sustained time periods.

Plain-language summary: Six studies involved availability interventions, of which four changed the relative proportion of less-healthy to healthier options, and two changed the absolute number of different options available. In statistical analyses that combined results from multiple studies, it was found that reducing the number of available options for a particular range or category of food(s) reduced selection of those food products (from analysing 154 participants) and possibly reduced consumption of those products (from 150 participants). However, the certainty of the evidence for these effects was low. Eighteen studies involved proximity interventions. Most (14/18) changed the distance at which a snack food or drink was placed from the participants, whilst four studies changed the order of meal components encountered along a line. One study found that this reduced selection of food (from analysing 41 participants), whilst in a statistical analysis combining results from multiple studies, it was found that placing food farther away reduced consumption of those food products (from analysing 1098 participants). However, the certainty of the evidence for these effects was very low and low, respectively. Key messages Mindful of its limitations, the current evidence suggests that changing the number of available food options or changing where foods are positioned could contribute to meaningful changes in behaviour, justifying policy actions to promote such changes to food environments. However, more high-quality studies in real-world settings are needed to make this finding more certain. How up-to-date is this review? The evidence is current to 23 July 2018.