Table 2.
Intervention effect on or association with meat demand
| Sample characteristics and study comparison | Intervention | Outcome | Results | |
|---|---|---|---|---|
| Provision of meat substitutes and meat-free foods | ||||
| Clark (2017)50 | Sample size: intervention group n=26 (shortest post-intervention follow-up), n=22 (longest post-intervention follow-up); age: median 27 years (IQR 24–32)*; female: 57%*; comparison: pre-post design | Intervention group: 12 week intervention; provision of meat substitutes, plant-based recipes, monthly motivational newsletter and emails; participants were asked to reduce consumption of red and processed meat by 50% | Red and processed meat consumption frequency (servings per week) the month before the intervention, the last intervention month, and 2 months after the intervention, assessed with a Food Frequency Questionnaire | Red and processed meat consumption was lower during the last intervention month (median 4, range <1–10) and 2 months after the intervention (average 6, range 1–14) than at baseline (median 10, range 2–20; p<0·001) |
| Flynn et al (2013)51 | Sample size: intervention group n=63†; age: mean 52 years (SD 17); female: 84%; comparison: pre-post design | Intervention group: 6 week intervention; provision of 22 plant-based recipes, sufficient meat-free foods to prepare three of the 22 recipes, weekly 30 min plant-based cooking demonstrations and taster sessions, and information that consuming meat daily is not necessary for health | Purchase of meat products (US$ spent on meat per week) during the 4 weeks before intervention and the 6 months after intervention, assessed by reviewing grocery receipts | $ per week spent on meat declined from baseline (mean 16·45, SD 2·20) to after intervention (mean 7·54, SD 0·71, p<0·001) |
| Holloway et al (2012)52 | Sample size: intervention group n=19; age: mean 21 years (SD 3)‡; female: 60%‡; comparison: pre-post design | Intervention group: 4 week intervention; provision of meat substitutes, 60 min information-based motivational event about vegetarianism, four face to face sessions to motivate lower meat intakes, plant-based recipes, and information about vegetarianism | Red and white meat consumption (g per day), assessed using a 7 day food diary before intervention and during the fourth week of the intervention | Red and white meat consumption was lower during the fourth week of the intervention (meanred≈27, meanwhite≈15) than at baseline (meanred≈78, p<0·001; meanwhite≈61, p<0·001)§ |
| Downsizing meat portions | ||||
| Reinders et al (2017)47 | Sample size (meal orders): intervention n=470, control: n=536; age: mean 48·6 years (SD 17·5); female: 54%; comparison: crossover, randomised controlled trial | Intervention: for 6 weeks the portion of meat (and fish) of selected meals was reduced by 12·5% and the portion of vegetables was doubled in three restaurants; control: 6 weeks of business as usual in the three restaurants | Meat consumption assessed subtracting the g of meat returned to the kitchen from the average g of meat in each of the targeted dishes | Meat consumption from the selected dishes was significantly lower during the intervention (mean 183·1, SE 2·52) than during the control period (mean 211·1, SE 2·29, p<0·001, ηp2=0·064) |
| Rolls et al (2010)48 | Sample size: n=48; age: mean 27 years; female: 50%; comparison: crossover, randomised controlled trial | Intervention meal: in a laboratory setting, participants were served a meal in which the meat component was reduced to 243 g, the grain component was reduced to 272 g, and the vegetable component was increased to 270 g, compared with a reference meal with 281 g meat, 326 g grains, and 180 g vegetables¶ | Meat consumption (in g), measured at each meal occasion weighing the meat serving before and after consumption | Meat consumption was lower during the intervention meals (mean 126·8, SD 48) than during the control meals (mean 145·4, SD 53·3, p<0·0001) |
| Rolls et al (2010)48 | Sample size: n=48; age: mean 27 years; female: 50%; comparison: crossover, randomised controlled trial | Intervention meal: In a laboratory setting, participants were served a meal in which the meat component was reduced to 187 g, the grain component was reduced to 217 g, and the vegetable component was increased to 360 g, compared with a reference meal with 281 g meat, 326 g grains, and 180 g vegetables¶ | Meat consumption (in g), measured at each meal occasion weighing the meat serving before and after consumption | Meat consumption was lower during the intervention meals (mean 125·2, SD 42) than during the control meals (mean 145·4, SD 53·3, p<0.0001). |
| Manipulation of the sensory properties of meat or alternatives | ||||
| Kunst and Hohle (2016), study 2b43 | Sample size: n=101; age: mean 35 years (SD 11); female: 60%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: participants viewed a picture of a pork roast with the pig's head; control group: participants viewed a picture of a pork roast without the pig's head | Participants indicated whether they would select a vegetarian dish instead of the pork roast on a scale from 0 (very unlikely) to 100 (very likely) | The demand for a vegetarian dish did not differ between the intervention group (mean 52·00, SE 5·56) and control group (mean 37·88, SE 5·11, p=0·065) |
| Kunst and Palacios Haugestad (2018), American sample44 | Sample size: n=178; Age: mean 36 years (SD 11)‖; female: 42%‖; comparison: intervention group vs control group, randomised controlled trial | Intervention group: participants viewed a picture of a pork roast with the pig's head; control group: participants viewed a picture of a pork roast without the pig's head | Participants indicated whether they would select a vegetarian dish instead of the pork roast on a scale from 0 (very unlikely) to 100 (very likely) | The demand for a vegetarian dish was higher in the intervention group (mean≈56, SE≈4) than in the control group (mean≈29, SE≈4, t[176]=5·22, p<0·001) |
| Kunst and Palacios Haugestad (2018), Ecuadorian sample44 | Sample size: n=183; age: mean 27 years (SD 9)**; female: 58%**; comparison: intervention group vs control group, randomised controlled trial | Intervention group: participants viewed a picture of a pork roast with the pig's head; control group: participants viewed a picture of a pork roast without the pig's head | Participants indicated whether they would select a vegetarian dish instead of the pork roast on a scale from 0 (very unlikely) to 100 (very likely) | The demand for a vegetarian dish was higher in the intervention group (mean≈46, SE≈4) than in the control group (mean≈33, SE≈45, t[181]=2·59, p=0·01) |
| Campbell-Arvai et al (2014)49 | Sample size: factor n=160, no factor n=160; age: NA; female: 53%; comparison: factor vs no factor, factorial randomised controlled trial | Factor (intervention group menus): food menus including five appealing meat-free options and a range of non-vegetarian dishes; no factor (control group menus): food menus including five less appealing meat-free options and a range of non-vegetarian dishes | Simulated food choices were dichotomised in meat options vs meat-free options | Participants viewing intervention group menus had lower odds of selecting meat options than did those viewing control group menus (OR 0·49, 95% CI 0·36–0·66) |
| Repositioning of meat | ||||
| Kongsbak et al (2016)42 | Sample size: intervention group n=33, control group: n=32; age: mean 24 years; female: 0%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: participants served themselves ad libitum from a buffet including, in order of appearance: standard size plates, salad components served in separate bowls, dressings, pasta, bread, and meatballs; control group: participants served themselves ad libitum from a buffet including, in order of appearance: standard size plates, pasta, bread, meatballs, mixed salad (ie, all the salad components served together), and dressings | Selection of meatballs (in g) assessed using radio frequency identification technologies of the intelligent buffet | Selection of meatballs did not differ significantly between the control group (mean 194·6, SD 78·6) and the intervention group (mean 156·2, SD 71·1; p=0·078), after adjusting for BMI, age, and selection of salad, pasta, and bread |
| Campbell-Arvai et al (2014)49 | Sample size: factor n=160, no factor n=160; age: NA; female: 53%; comparison: factor vs no factor, factorial randomised controlled trial | Factor (intervention group menus): food menus from which the meat options were removed and repositioned on a board 3·5 m away; no factor (control group menus): food menus containing a range of meat-free and meat-based options | Simulated food choices were dichotomised in meat options vs meat-free options | Participants viewing intervention group menus had lower odds of selecting meat options than did those viewing control group menus (OR 0·24, 95% CI 0·18–0·36) |
| Stewart et al (2016), study 238 | Sample size: orders during the intervention period n=384 (227 meat orders, 157 meat-free orders); orders during the control period n=398 (346 meat orders, 52 meat-free orders); age: NA; female: NA; comparison: multiple treatment reversal | Intervention period: meat options appeared after meat-free options in two university online meal booking systems over 3 observation weeks; control period: meat options appeared before meat-free options in two university online meal booking systems over 3 observation weeks | Number of meat-containing meals (including fish) and meat-free meals purchased | Adjusted for college site, meal purchases over the intervention period had 0·12 times the odds of containing meat compared with meals purchased during the control period (OR 0·12, 95% CI 0·08–0·18; p<0·001)††; the likelihood of selecting a meat option was significantly higher in one of the two college sites at which the intervention was tested |
| Stewart et al (2016), study 338 | Sample size: orders during the intervention period n=31 (26 meat orders, five meat-free orders); orders during the control period n=35 (30 meat orders, five meat-free orders); age: NA; female: NA; comparison: multiple treatment reversal | Intervention period: for 2 weeks meat-free options were repositioned to be the default option in a university online meal booking system; students not actively changing their selection to the meat option were served a plant-based meal; control period: for 2 weeks meat options were left as the default option in a university online meal booking system; students not actively changing their selection to vegetarian were served meat | Number of meat-containing meals (including fish) and meat-free meals purchased | Meal purchases over the intervention period had 0·87 times the odds of containing meat compared with meals purchased over the control period, but this effect did not reach statistical significance (OR 0·87, 95% CI 0·23–3·33, p=0·87)†† |
| Manipulating the description or labelling of meat or alternatives | ||||
| Bacon and Krpan (2018)41 | Sample size: intervention group n=185, control group n=194; age: mean 36 years; female: 51%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: food menu containing three meat and five meat-free options, in which the description of the first meat-free dish was changed from “Risotto Primavera” to “Fresh Seasonal Risotto Primavera”; control group: food menu containing three meat and five meat-free options | Simulated food choices were dichotomised into meat options (chicken cacciatora, steak frites, or hamburger) vs meat-free options | The odds of selecting a meat option did not differ between the intervention group and the control group (OR 1·1, p=0·677) |
| Bacon and Krpan (2018)41 | Sample size: intervention group n=185, control group: n=194; age: mean 35 years; female: 52%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: food menu that contained three meat and five meat-free options, in which the first meat-free dish (ie, “Risotto Primavera”) was highlighted as the “Chef's recommendation”; control group: food menu containing three meat and five meat-free options | Simulated food choices were dichotomised into meat options (chicken cacciatora, steak frites, or hamburger) vs meat-free options | The odds of selecting a meat-based meal did not differ between intervention group and control group (OR 1·37, p=0·180) |
| Kunst and Hohle (2016), study 543 | Sample size: n=190; age: mean 34 years (SD 10); female: 52%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: food menu with eight meat-based meals, which were described as “cow” and “pig” options; control group: food menu with eight meat-based meals, which were described as “beef” and “pork” options | Participants indicated whether they would select a meat-free meal instead of the meat options on a scale from 0 (very unlikely) to 100 (very likely) | The demand for meat-free meals did not differ between the intervention group (mean 43·12, SE 3·84) and the control group (mean 33·78, SE 3·49, p=0·074) |
| Campbell-Arvai et al (2014)49 | Sample size: factor n=160, no factor n=160; age: NA; female: 53%; comparison: factor vs no factor, factorial randomised controlled trial | Factor (intervention group menus): food menus containing a range of meat-based options and meat-free options that were differentiated with a leaf symbol indicating that eating less meat can help reduce our environmental impact; no factor (control groups menus): food menus containing a range of meat-free and meat-based options | Simulated food choices were dichotomised into meat options vs meat-free options. | The odds of selecting a meat-based dish did not differ between participants viewing the intervention group or the control group menus (OR 0·92, 95% CI 0·69–1·2) |
| Stewart et al (2016), study 138 | Sample size: orders during intervention period n=2784 (2373 meat orders, 411 meat-free orders); orders during control period n=2496 (2177 meat orders, 319 meat-free orders); age: NA; female: NA; comparison: multiple treatment reversal | Intervention group period: meat options were labelled as “meat” instead of “standard” or “normal” in four university online meal booking systems over 12 observation weeks; control group period: meat options were labelled as “standard” or “normal” in four university online booking systems over 12 observation weeks | Number of meat-containing meals (including fish) and meat-free meals purchased | Adjusted for college site, meal purchases over the intervention group period had 0·83 times the odds of containing meat compared with meals purchased over the control group period (OR 0·83, 95% CI 0·71–0·98, p=0·02)††; the likelihood of selecting a meat option was significantly higher in some colleges compared with others |
| Pricing | ||||
| Vermeer et al (2010)46 | Sample size: n=137; age: mean 25 years (SD 10); female: 66%; comparison: intervention group vs control group, randomised controlled trials | Intervention group: three portions of chicken nuggets were priced with a proportional system—€2·35 for a small portion, €3·50 for a medium portion, and €5·80 for a large portion; control group: three portions of chicken nuggets were priced with a value system—€2·75 for a small portion, €3·50 for a medium portion, and €5·00 for a large portion | Simulated selection of small, medium, or large portion of nuggets was dichotomised in small vs other and in large vs other | Authors found no effect of pricing on the selection of different portion sizes among the general population |
| Multicomponent changes to the micro-environment | ||||
| McClain et al (2013)45 | Dining halls: intervention group n=2, control group n=2; questionnaire responses: intervention group n=247; control group n=278‡‡; age: 20 years; female: 53%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: 4 week marketing campaign featuring flyers, labels, healthy choice indicators of meat-free foods, and sample meat-free dishes at the entrance of the canteen; control group: 4 weeks of business as usual | Consumption frequency of high-fat meats (in servings per week) assessed at the baseline and directly after the intervention with a food frequency questionnaire | In the control group high-fat meat intake increased by 0·9 servings per week, while it decreased by 0·9 servings per week in the intervention group (time × condition interaction: p=0·04) |
| Sorensen et al (2005)39 | Small businesses: intervention group n=13, control group n=13; questionnaire responses: intervention group n=807, control group n=933‡‡; age (adjusted for worksite clustering): intervention group 44 years, control group 43 years; female: 33%; comparison: intervention group vs control group, randomised controlled trial | Intervention group: 18 month multicomponent intervention to reduce red meat intake and smoking and to increase physical activity, fruit, vegetable, and multivitamin intake; specific interventions were designed within each worksite under the advice of a hygienist, and included policies aimed at offering healthful food options at company meetings, system oriented interventions, interactive activities, and education; control group: smoking cessation services | Consumption frequency of red meat (in servings per week) assessed with a food frequency questionnaire at baseline and directly after intervention; responses were dichotomised in ≤3 servings per week vs >3 servings per week | The change in percentage of participants eating ≤3 servings per week of red meat did not differ between the intervention group (+4·1%) and control group (+3%) after adjusting for worksite clustering (p=0·72) |
≈ indicates results were read from figures or graphs. NA=not available. OR=odds ratio. BMI=body-mass index.
*
Baseline characteristics of the 37 participants completing some secondary outcomes extracted from the doctoral thesis on which the study was based.
†
Only 60 participants provided a complete set of grocery receipts at both timepoints.
‡
Of the 25 participants recruited at baseline.
§
Results were based on an independent sample t test, while a dependent sample t test should be used for pre-post designs.
¶
Both control and intervention meals were served to each participant on two different occasions varying the energy content of the vegetable component. For the aim of this review participants' average consumption was defined as their average consumption across the two energy-varied meals.
‖
Of the 201 participants enrolled.
**
Of the 202 participants enrolled.
††
A logistic regression analysis was done of the basis of raw data available from the unpublished report.
‡‡
Questionnaires were not always completed by the same individuals at baseline and at follow-up.