We identified 8126 studies, of which 2305 were duplicates, and screened all non-duplicate studies by title and abstract (see Figure 1). We screened the full text of 164 studies. Of these, we excluded three conference abstracts, 12 cross-sectional studies, 40 studies not concerning the Great Recession, six studies not in English, 24 studies not reporting primary empirical data, 31 studies where the outcome was related to nutrition, and 18 studies with partial measures of dietary intakes ie. general expenditure on food at home. 30 studies were included after full text screening, plus two from grey literature and nine from reference lists to include 41 studies overall (Figure 1) (26-66). Table 1 presents characteristics of the 41 included studies.
Figure 1: Study Selection
Studies with a total of 2.6 million people from 25 countries were included: 12 high income, nine middle income, and four low income(67). Studies were heterogeneous regarding exposures, methods, and locations. Outcomes were also heterogeneous, but broadly fell into four categories:
- energy intake (10 studies),
- dietary quality (11 studies),
- food intake and foods high in sugar, salt and fat (34 studies),
- macronutrients (15 studies).
Study Quality and Characteristics
The majority of studies were of high or medium quality: eighteen studies (44%) were high quality, fifteen (37%) medium quality, and eight (19%) low quality. Only four studies investigated the impact of the Great Recession on children’s dietary intakes (32, 35, 46, 47). Most studies used individual-level data from pre-existing, nationally representative surveys, except for one study which used ecological data on calorie and protein intake per capita and currency movements (36). Thirty-one studies were serial cross-sectional (26-28, 30-35, 37-39, 42-45, 48-52, 54-56, 58-61, 64-66) and eight were cohort studies (29, 40, 41, 46, 47, 57, 62, 63). Thirteen studies (29%) used macroeconomic measures as the exposure such as unemployment rates, Consumer Confidence Index and neighbourhood characteristics (29, 31, 36, 41-44, 55-59, 64). Twenty-nine studies (71%) used commencement of the Great Recession as the exposure – this was the most common exposure measure for all four outcome categories. Most used regression methods with dummy time variables (27, 28, 30, 32-35, 37, 40, 41, 46, 51, 52, 54, 60-63, 65, 66). Others included using Difference-in Difference, t-tests, ANOVAs, and time-varying Almost Ideal Demand System and Bai Perron tests (26, 38, 39, 45, 47-49, 53, 54). Most studies adjusted for covariates including age, sex, education and socio-economic status – this was taken into account through the study quality assessment and we analysed adjusted results where possible. An additional file shows gives more detail on the studies [see Additional file 2]. Key findings are summarised in Table 2.
Ten studies assessed changes in energy intake, generally located in high and middle income countries (27-29, 35, 36, 39, 44, 45, 48, 60). Seven used daily calorie intake as the outcome (28, 35, 39, 44, 45, 47, 60), while one used monthly intake in kJ (29) and one examined changes in growth rates using non-individual data (36). For one study based in seven different countries in Latin America, only data from Guatemala was available from the authors (44). We were unable to obtain standard deviations for a UK study so this was omitted from the meta-analysis, as was a Danish study assessing how Consumer Confidence Index affects energy intake (29, 48). Seven studies were included in our random effects meta-analysis (28, 35, 39, 44, 45, 60). We found that overall, energy intake decreased by 39.9 calories per adult equivalent per day (95% Confidence Interval: -119.9, 40.2) over the Great Recession (see Figure 2). The I2 statistic for heterogeneity was 95.9%, suggesting considerable heterogeneity. When only high-income countries (USA and Italy) (27, 28, 35, 39, 60) were included in the meta-analysis, energy intake decreased by 103.0 calories per adult equivalent per day (95% Confidence Interval: -132.1, -73.9) with a lower I2 statistic of 50.6%. When the meta-analysis was run for middle-income countries (Guatemala and Pakistan (44, 45)), energy intake increased by 105.5 calories per adult per day (95% confidence Interval: 72.8, 138.2), with an I2 statistic of 0.0%, indicating very low heterogeneity.
The decrease in energy intake in high-income countries was supported by studies not included in the meta-analysis. A Danish study also reported that decreasing Consumer Confidence Index as a proxy for the recession was associated with lower monthly energy intake (29). Similarly, a UK study reported a decrease of 26 calories per day (48). The only study investigating children’s daily energy intake suggested that children experienced larger decreases than adults (210 calories per capita per day) (35). Two studies observed a decrease in food expenditure alongside the decrease in calories (29, 47). Decreases in calories were also accompanied by decreases in consumption of several different food groups and macronutrients, although the types of foods decreasing were not consistent (see below for further details) (29, 39, 47, 60).
Figure 2: Forest Plot for change in total energy intake per adult per day in calories.
Eleven studies examined the impact of the recession on dietary quality using indices of dietary quality and diversity (28, 34, 38, 40, 45-47, 49, 56, 59, 60). These studies were generally located in high and low income countries. Outcomes were heterogeneous, including Dietary Diversity Score (38, 45), Food Consumption Score (45, 59), and Healthy Eating Index (HEI) (46, 47). Eight studies (two of which were of high quality) reported negative impacts (28, 34, 38, 46, 49, 56, 59, 60) and three (all high quality) reported positive impacts (40, 45, 47) on dietary indices (Figure 3). Overall findings suggest a decrease in dietary quality over the Great Recession. There was little consistency across measures, for example Food Consumption Score decreased in Haiti but did not significantly change in Bangladesh (45, 59). There was also little consistency within countries. For example, in the UK, one study found that HEI improved by 1.5% over the recession, however, this increase masked a shift away from vegetables, grains, milk, and meat which was offset by a lower calorie share of saturated fat and lower salt consumption (47). An earlier paper using a different dataset over the same time period found a similar decrease in saturated fat intake and fruit and vegetable consumption, but a 1% decrease in HEI (46). Antioxidant consumption score decreased alongside a decrease in Mediterranean Diet score between 2005-2006 and 2007-2010 in Italy, suggesting a decrease in dietary quality (60).
Figure 3: Harvest plot for studies assessing dietary quality. Each bar represents a single study, with the height of the bar representing study quality via the Newcastle Ottawa Scale. The x axis indicates effect direction.
Thirty-four studies reported on food intake, generally located in high and middle income countries (26-33, 35, 37, 38, 41-43, 45-48, 50-58, 60-66). The most common outcome was consumption of a food group or an amount of food as a binary outcome per day/week (33, 37, 51, 52, 54, 55, 61, 65, 66). Other commonly used outcome measures included expenditure or frequency of consumption in a specified time period (29, 32, 41, 43, 48, 50, 56, 57, 62-64) or share of calories or calorie intake from food groups(27, 28, 35, 45, 47, 48). Overall, consumption of fruits and vegetables, meat and fish, fast food, sugary products, and soft drinks decreased during the recession, with egg and legume consumption increasing and sources of carbohydrate consumption unchanged. We found mixed results regarding intake of dairy, oils and fats, and snacks. Results were generally consistent by study quality. Harvest Plots for all outcomes can be found in Additional File 3.
Eight studies examined fruit and vegetable consumption combined, four of which found decreases in fruit and vegetable consumption (46, 48, 51, 55) and two found no significant impact (33, 52). Two studies found increases in fruit and vegetable consumption, although both were of low quality (31, 58). Fourteen of the eighteen studies on fruit intake alone found that this decreased over the Great Recession (Figure 4) (29, 30, 38, 41-43, 54, 56, 61-63, 65, 66). One reported little impact (53) and three reported increases in fruit intake (45, 47, 50). All studies examining whether individuals consumed fruit daily reported decreases in fruit consumption (38, 43, 54, 61-63, 65, 66). Fifteen studies investigated the impact of the Great Recession on vegetable intake (Figure 5). Nine reported decreases in vegetable intake (41, 42, 47, 54, 56, 61, 63-65) and three reported no significant impacts (29, 37, 38). A Spanish study observed a decrease in daily vegetable consumption that was only significant in women without an educational qualification (61). One UK study found a 7.8% decrease in share of calories from vegetables (47) while another UK study found a small and weakly significant increase in portions of vegetables eaten per day in the UK (43). A study in Spain found that the odds of eating vegetables daily increased between 2006 and 2012 (66). In Pakistan, expenditure on vegetables increased slightly, but less than wheat and rice expenditure (30).
Figure 4: Harvest plot for studies assessing fruit intake. Each bar represents a single study, with the height of the bar representing study quality via the Newcastle Ottawa Scale. The x axis indicates effect direction.
Figure 5: harvest plot for studies assessing vegetable intake. Each bar represents a single study, with the height of the bar representing study quality via the Newcastle Ottawa Scale. The x axis indicates effect direction.
Five of eleven studies on sources of carbohydrates reported no change (29, 38, 41, 53, 65) and four reported differing directions of associations suggestive of within-category substitutions (45, 47, 48, 50) (Additional File 3 A1). An overall decrease (64) and increase (30) in expenditure on sources of carbohydrates was seen in one study each. Eleven studies examined dairy consumption (Additional File 3 A2) with mixed results. Five studies reported decreases (29, 38, 41, 53, 64) and two reported increases (30, 50), while one reported no change (37) and two reported increases in cheese but decreases in milk products (47, 48). Patterns were inconsistent across income groups in the US (26). Nine studies examined consumption of fats and oils (Additional File 3 A3) (29, 30, 38, 47, 48, 50, 53, 60, 64). Only one study found that oil consumption decreased (47); monthly purchases of fats decreased in Denmark, but not oils (29). Expenditure on fats and oils increased in Pakistan and Poland (30, 50). The remaining five studies found mixed or null results (38, 48, 53, 60, 64).
Sixteen studies investigated intake of sources of proteins (26, 29, 30, 37, 38, 41, 45, 47, 48, 50, 53, 54, 60, 61, 64, 65). While most studies examined consumption of protein sources separately, share of calories from poultry and fish increased while calories from red meat and nuts decreased in the UK (47). Expenditure on meat, poultry, and fish increased in Pakistan (30) but decreased in Russia (41). Animal proteins per day increased but vegetarian proteins decreased in Italy (60). Twelve studies examined meat consumption (Additional File 3 A4). Seven reported decreases (with consistent results in Spain and the UK) (38, 41, 47, 48, 54, 61, 64), one reported an increase (50), two reported no change (37, 65) and two reported mixed results (26, 29). Eleven studies reported on fish consumption (Additional File 3 A5). Six reported decreases over the recession (29, 38, 48, 54, 64, 65), one reported an increase (26), two reported no association (37, 61) and two reported differential effects including a decrease in fish but an increase in seafood in Poland (45, 50). Potential substitution of high cost fish for low cost fish was reported in Bangladesh (45). Three of five studies reporting on egg consumption reported increases (Additional File 3 A6) (26, 29, 38, 48, 50). Consumption of beans, legumes, and pulses significantly increased in five of the six studies it was investigated in (30, 38, 45, 61, 65), with one US study reporting no change (26).
Eight studies examined the impact of the recession on fast food (Additional File 3 A7) - seven reported a decrease in consumption (27, 28, 32, 48, 57, 62, 63) and one reported no change (56). Food at restaurants, cafes, bars, bistros, fast food outlets, and takeaways decreased in the UK, but share of calories from prepared savoury foods and ready meals increased (48). There was an increase in calories from Consumer Packaged Goods (especially for households with children) in the USA (35). Consumer Confidence Index was not associated with processed food consumption in Denmark (29). Six studies reported on snack consumption (Additional File 3 A8). Three found increases in snack consumption (29, 55, 56), two found mixed results suggestive of decreases (27, 28) and one found no significant change (57). Higher area-level unemployment rate was associated with increase in snack consumption in the USA and Italy (55, 56). There was no significant change in total snacks consumed but a significant decrease in snacks eaten away from home in the USA (27, 28).
Eleven studies examined the Great Recession’s impact on consumption of sugary products such as desserts and confectionary (Additional File 3 A9); seven reported decreases (29, 48, 54, 62-64, 66), two reported increases (47, 65) and two reported no significant change (56, 61). Calories from confectionary, soft drinks, sugary products, and preserves consumed in and out of the home decreased in one UK study (48). However, a UK study by the same authors found that share of calories from prepared sweets increased (47). Eight studies examined the impact of the Great Recession on non-alcoholic beverage consumption (Additional File 3 A10), primarily concerning soft drinks and fruit juice (29, 35, 47, 56, 57, 62, 63, 66). All reported decreases in consumption of beverages, although for two this decrease was not significant.
Fifteen studies – from high, middle, and low income countries – assessed consumption of macronutrients with generally mixed results (27-30, 36, 38, 39, 45-47, 50, 58, 60, 62, 63). Macronutrient outcomes included calories (and share of calories) from macronutrient (27, 28, 45, 47), grams per day/month or grams per 100g (27-29, 39, 46), and price elasticity (36). For sugar consumption, measures also included percentage change in sugar consumption, budget share, and expenditure on sugar (29, 30, 38, 39, 46, 47, 50, 58).
Four studies reported on carbohydrate consumption (Additional File 3 A11) - two reported decreases ranging from 3.3g to 16g per day (39, 60), one reported a slight increase (47), and one reported no significant change (29). Eight studies examined sugar intake (Additional File 3 A12), although for many of these it was unclear whether they were examining added sugar or general dietary sugar intake (29, 30, 38, 39, 46, 47, 50, 58). Four found that sugar intake increased (30, 46, 48, 58) while three studies identified decreases (38, 39, 50). For example, UK households increased their overall sugar intake by 0.20g per 100g, but for households with children this increase was by 0.44g per 100g increase (an increase of ~6g per day) (46).
Seven studies examined protein intakes (Figure A13) and four reported decreases (29, 36, 39, 47), two reported small increases(46, 60) and one reported no change (45). In one US study, protein intakes significantly decreased (by ~ 4g) only in men (39). Four studies reported on total fat consumption and saturated fat consumption (Additional File 3 A14 and A15) (27, 29, 39, 60). Directions of patterns were consistent within studies but different between studies, with increases (60), decreases (29), and no significant changes reported (27, 28). In the UK, the share of calories from unsaturated fats increased slightly alongside a decrease in share of calories from saturated fats in one study, although in a separate study there was a small increase in saturated fat consumption, particularly in pensioners (46, 47). Total daily fat intakes decreased by ~3g in women only in the USA (39). Additionally, there was no significant change in cholesterol consumption in the USA (27, 28). Three of five studies reported decreases in dietary fibre over the Great Recession (27, 28, 60); one reported no significant change (29) and one UK study observing an increase (47) (Additional File 3 A16).
Seventeen studies examined inequalities including high, middle, and low income nations (26-33, 35, 37, 38, 41-43, 45-48, 50-58, 60-65). Two studies assessed calorie intakes, four dietary quality, twelve food intake, and one macronutrients. Inequalities were operationalised in terms of education, income/wealth, social class, or job type. Fourteen studies found that the recession led to greater changes in dietary intakes for low SEP individuals (26, 30, 34, 42, 44, 45, 50, 51, 53, 54, 56, 60, 61, 65, 66). Results were consistent for fruit and vegetable intake (42, 50, 51, 54, 56, 61, 66) while patterns of meat and fish consumption were less clear but generally suggestive of inequalities (26, 54, 61, 65). Results were more mixed for fast food consumption (32, 56). The Great Recession also seems to have increased already existing inequalities in dietary quality (34, 45, 60), except for one UK study which found that lower income households improved their HEI score the most (47). Only four studies investigated the impact on children’s dietary intakes so we were unable to make meaningful conclusions regarding this subgroup (32, 35, 46, 47).