A stepped-wedge randomised controlled trial

A complete of 19 worksite cafeterias have been recruited by means of a significant UK grocery store chain (see Fig 1) and have been based mostly inside their distribution centres. The distribution centres have been sometimes in distant places with no native meals shops to buy meals or drink. Apart from the cafeteria—the situation during which we intervened—the one choices have been merchandising machines (containing snacks and drinks) and bringing in meals from dwelling. There have been 3 eligibility standards: They wanted (i) to be positioned in Nice Britain; (ii) to have at the least 350 staff based mostly on the web site; and (iii) to have digital point-of-sale tills to report gross sales knowledge. A complete of 29 cafeterias have been screened for eligibility, and 19 participated within the examine (Fig 1). The taking part websites housed 1 cafeteria every and employed between 561 and a pair of,357 workers (20,327 in whole), most of whom have been employed in guide jobs (see Table 1). The taking part cafeterias have been managed by 3 catering corporations: one firm managed 10 cafeterias, one managed 5, and one managed 4.

The pattern measurement calculation was based mostly on knowledge from 2 related research [14,15]. We conservatively used the most important estimate of SD (0.111) when evaluation was on the log scale. A one-sided t check at 80% energy with 5% significance degree would require n = 19 cafeterias to detect an impact measurement of 6.5% or higher discount in vitality bought. We chosen a one-sided check, reflecting current proof [12–15].

The provision intervention was carried out in isolation (i.e., with out measurement) in the course of the availability interval. Within the present examine, this intervention comprised reducing the variety of greater vitality foods and drinks merchandise and growing the variety of decrease vitality foods and drinks merchandise to take care of the identical whole variety of merchandise, i.e., altering the relative availability [17]. Within the TIPPME [11], that is categorized as an availability × product intervention.

Cutoff factors in vitality content material by product sort have been prespecified to determine merchandise that may very well be eliminated and those who may very well be added (see Desk A in S1 Text). The deliberate diploma of implementation—resembling lowering greater vitality candy snacks from 90% to 80%—was negotiated with the catering suppliers and was primarily decided by their capability to acquire decrease vitality choices. It was doable to use the provision intervention to 7 foods and drinks classes, which made up 54% of all vitality bought:

1. important meals (e.g., lasagna);
2. aspect dishes (e.g., rice);
3. chilly drinks (e.g., can of cola);
4. candy snacks (e.g., chocolate bar);
5. savoury snacks (e.g., crisps);
6. desserts (e.g., pot of chocolate mousse); and
7. bakery objects (e.g., slice of Victoria sponge cake).

Additional classes that weren’t focused included breakfasts, soups, salads, and sandwiches, because it was not doable to intervene in these classes. Sandwiches have been initially deliberate to be focused for the provision intervention; nevertheless, it was subsequently found that there have been contracts that prevented eradicating sandwiches from sale. The deliberate implementation was based mostly on our pilot examine [14]. The intervention traits are proven in Table 2 and S1 and S2 Information.

For the provision plus measurement interval, the provision intervention was maintained, and the dimensions intervention was carried out. The scale intervention comprised lowering the portion measurement, by quantity, of merchandise in focused meals classes. Throughout the TIPPME intervention typology [11], that is categorized as a measurement × product intervention.

Modifications have been made solely to merchandise in these 4 classes that have been categorized as greater vitality utilizing the cutoffs in Desk A in S1 Text. The deliberate reductions in portion measurement various by cafeteria and product, however have been requested to be at the least a ten% discount in quantity for every focused product. We additionally requested that any discount in portion measurement was accompanied by a proportionate change in value to keep away from confounding a change in measurement with a change in worth for cash. This request to cut back the value was not granted because the merchandise have been already subsidised.

A stepped-wedge design was used throughout a interval of 25 weeks (27.05.19 to 18.11.19). Such designs are sometimes most well-liked to a parallel teams randomised managed trial (RCT) when examine sources solely permit a staggered implementation of the intervention(s). Every of the 19 cafeterias was randomly allotted to the week during which the intervention was carried out (see Fig 2). The baseline interval lasted between 4 and 13 weeks, relying on the randomisation order of every cafeteria. Weeks 1 to 4 comprised the minimal baseline interval. From Week 5 till Week 13, 2 cafeterias per week carried out the primary intervention—availability. There was no hole between steps; interventions have been carried out on the primary day of the intervention durations. In Week 14, the final cafeteria (quantity 19) carried out the provision intervention. The provision intervention interval lasted 8 weeks for all cafeterias. From Week 13 till Week 21, 2 cafeterias per week carried out the second intervention—measurement—whereas persevering with the provision intervention. In Week 22, the final cafeteria carried out the dimensions intervention. The interventions continued for all cafeterias till the tip of Week 25, as deliberate. The provision plus measurement intervention interval, due to this fact, lasted 4 to 13 weeks, relying on the randomisation order of every cafeteria.

Generalised additive linear combined fashions [19] have been used to estimate the general potential affect of the provision intervention and the mixed availability plus measurement intervention in comparison with baseline. Cafeterias have been fitted as random results, with the impact of the day of the week allowed to range by cafeteria as a random nested time period. In additive fashions, cafeterias had markedly completely different variability (heteroscedasticity), which required modelling. Day quantity throughout every intervention (normalised inside every cafeteria to make sure equal weighting between cafeterias) was used to permit for the becoming of three separate total time traits. The identification hyperlink operate (i.e., regular distribution) was used for modelling the imply, and the sigma hyperlink operate (i.e., log10) was used for modelling the variance.

To guage the distinction in affect between the two interventions somewhat than baseline, the mannequin was rerun with availability as an alternative of baseline used because the reference group resulting in the identical mannequin match. Mannequin diagnostics have been assessed utilizing variance inflation components, residual plots, and quantile–quantile (Q–Q) plots for GLMM and additive fashions, and, additionally, worm plots and correlation operate plots for the additive fashions, and these diagnostics have been acceptable. Additional analyses describing formal checks of replication and moderators will be present in S1 Text.

The constancy checks steered that the provision and measurement interventions have been largely carried out as meant. The general success fee at attaining the provision targets was 76%. This was calculated by figuring out the proportion of intervention classes that met the provision intervention targets at every web site go to for every cafeteria. Amongst intervention class merchandise, there have been 58% greater vitality merchandise out there in cafeterias throughout baseline, which decreased to 50% throughout availability and 47% throughout availability plus measurement. The success fee of implementing the dimensions intervention was 83%. This was calculated by figuring out the proportion of intervention classes that met the dimensions intervention targets at every web site go to for every cafeteria. Throughout the measurement intervention, 7% of intervention class merchandise being offered throughout a typical day have been shrunk by a median of 14%. The proportion of merchandise modified was greater for important meals (25% [0.8/3.4 main meals per day]) and sides (42% [2.8/6.7 sides per day]), the classes from which most vitality was bought. See Table 2 and S1 Text for additional particulars.

The impact of the provision intervention was a discount in vitality bought, relative to baseline, of −4.8% (95% CI −7.0% to −2.7%), p < 0.001. The impact of the provision plus measurement intervention, relative to baseline, was a discount of −11.5% (95% CI −13.7% to −9.3%), p < 0.001. These outcomes are proven in Fig 3, and the unadjusted knowledge are proven in Table 3.

Fig 3. The consequences of availability and availability plus measurement on vitality (kcals) bought per day relative to baseline.

Error bars signify 95% CIs for the general results and 99.9% CIs (Bonferroni adjustment) for the location results.

https://doi.org/10.1371/journal.pmed.1003743.g003

The complete fashions (reported in S1 Text) additionally present nonsignificant total time traits for baseline, B = −1,841.35, SE = 1,605.49, p = 0.252; availability, B = −174.31, SE = 467.23, p = 0.709; and availability plus measurement, B = −157.38, SE = 244.14, p = 0.519, suggesting that on common, the consequences of every intervention are maintained over time.

The principle strengths of this examine are its design and execution. Though there was variation, each web site carried out the provision and measurement interventions to some extent, and a big majority met the prespecified targets. The first and secondary outcomes within the present examine have been measured objectively utilizing buying knowledge from digital point-of-sale tills. The corporate that supplied the gross sales knowledge have been unable to offer individual-level knowledge due their knowledge privateness guidelines. We due to this fact have no idea the extent to which completely different transactions represented completely different clients. Whereas our main end result was vitality bought—not vitality consumed—individuals are likely to eat roughly 90% of meals that they choose in related settings [28,29], which means that gross sales are good proxy for consumption. There have additionally been considerations that such interventions might result in compensatory consumption resembling by buying extra snacks later within the day; experimental research discover that lowering the portion measurement of meals doesn’t have this impact [30–33]. It’s unknown if compensation results did happen in our examine as we didn’t check for this; nevertheless, the web impact of the interventions was a discount in vitality bought. There have been additional considerations by catering workers that the modifications wouldn’t be acceptable to clients. Nonetheless, as soon as the examine began, only a few feedback or complaints have been delivered to our consideration. The provision intervention concerned changing some greater vitality merchandise with decrease vitality ones. Whereas that is conceptually distinguished from an intervention during which the location of things is systematically altered, the act of eradicating and changing merchandise can also change the location of the merchandise on sale—with websites requested to put more healthy merchandise the place much less wholesome ones have been beforehand. Whereas altering the order of merchandise might have an effect on meals choice and buying [12], it’s unclear whether or not modifications to placement necessitated within the availability intervention might have contributed to the impact noticed, significantly given variation in web site structure and shows often that includes a mixture of the more healthy versus much less wholesome choices inside the examine classes investigated.

The present examine offers proof that these modifications are efficient in a setting primarily utilized by guide employees, so—offering these should not discovered to be disproportionately simpler for nonmanual employees—the present interventions could be unlikely to exacerbate and will cut back current well being inequalities [6,34].

A evaluation of vitality overconsumption suggests {that a} discount of solely 28 kcals consumed per individual, per day, could be enough to stop additional weight achieve in 90% of the inhabitants [35]. Due to this fact, if cafeterias in worksites, colleges, and universities carried out these modifications, this might assist cut back overconsumption of vitality and due to this fact help in widespread efforts to cut back population-level weight problems equitably. UK authorities pointers for catering in public sector establishments already embrace greatest apply pointers, which embrace availability and measurement standards for snacks and for sugar-sweetened drinks [36]. Extending these pointers to incorporate suggestions for different merchandise is now warranted, significantly for important meals that contribute the most important share of energy to meals purchases in worksite cafeterias.

These meaning to implement these insurance policies ought to take into accounts the variety of merchandise focused and the extent to which they’re shrunk, as higher reductions in measurement ought to result in higher discount in vitality consumption [37]. Whereas difficult to implement, making use of the modifications to extra merchandise would restrict the power of shoppers to pick out the remaining greater vitality choices. The provision intervention concerned altering the proportion of upper vitality merchandise from 58% to 50%. Though it’s doubtless that making higher modifications than this may result in higher reductions in vitality buying and consumption, there isn’t a direct proof but to substantiate this speculation.

The three key uncertainties that stay concern the long-term upkeep of results, the optimum traits of the interventions, and the particular contexts during which the interventions are simplest. First, though the present examine was the most important and longest of its type (to our data), additional evaluations are wanted to substantiate that the interventions will proceed to exert their results over a yr or extra. Second, the present examine didn’t check the optimum diploma of implementation. Future analysis might estimate the impact of experimentally various the diploma of implementation, significantly for availability interventions, the place much less analysis has been performed. Third, the present examine reveals that the interventions are efficient in worksite cafeterias with predominantly guide employees, which extends additional research exhibiting effectiveness in cafeterias catering to a combination of workplace and guide employees [14,15], in college cafeterias [38], and in a childcare centre [39]. Additional analysis in different out-of-home settings, resembling quick meals shops and eating places, would decide whether or not there are limits to, or key traits related to, the settings during which the interventions are efficient.