BackgroundWhile food pricing is a promising strategy to improve diet, the prospective impact of food pricing on diet has not been systematically quantified.ObjectiveTo quantify the prospective effect of changes in food prices on dietary consumption.DesignWe systematically searched online databases for interventional or prospective observational studies of price change and diet; we also searched for studies evaluating adiposity as a secondary outcome. Studies were excluded if price data were collected before 1990. Data were extracted independently and in duplicate. Findings were pooled using DerSimonian-Laird's random effects model. Pre-specified sources of heterogeneity were analyzed using meta-regression; and potential for publication bias, by funnel plots, Begg's and Egger's tests.ResultsFrom 3,163 identified abstracts, 23 interventional studies and 7 prospective cohorts with 37 intervention arms met inclusion criteria. In pooled analyses, a 10% decrease in price (i.e., subsidy) increased consumption of healthful foods by 12% (95%CI = 10–15%; N = 22 studies/intervention arms) whereas a 10% increase price (i.e. tax) decreased consumption of unhealthful foods by 6% (95%CI = 4–8%; N = 15). By food group, subsidies increased intake of fruits and vegetables by 14% (95%CI = 11–17%; N = 9); and other healthful foods, by 16% (95%CI = 10–23%; N = 10); without significant effects on more healthful beverages (-3%; 95%CI = -16-11%; N = 3). Each 10% price increase reduced sugar-sweetened beverage intake by 7% (95%CI = 3–10%; N = 5); fast foods, by 3% (95%CI = 1–5%; N = 3); and other unhealthful foods, by 9% (95%CI = 6–12%; N = 3). Changes in price of fruits and vegetables reduced body mass index (-0.04 kg/m2 per 10% price decrease, 95%CI = -0.08–0 kg/m2; N = 4); price changes for sugar-sweetened beverages or fast foods did not significantly alter body mass index, based on 4 studies. Meta-regression identified direction of price change (tax vs. subsidy), number of intervention components, intervention duration, and study quality score as significant sources of heterogeneity (P-heterogeneity<0.05 each). Evidence for publication bias was not observed.ConclusionsThese prospective results, largely from interventional studies, support efficacy of subsidies to increase consumption of healthful foods; and taxation to reduce intake of unhealthful beverages and foods. Use of subsidies and combined multicomponent interventions appear most effective.

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Background: While food pricing is a promising strategy to improve diet and reduce cardiometabolic disease, most prior evidence comes from cross-sectional price elasticity estimates. The prospective impact of food pricing on dietary behaviors and obesity has not been systematically evaluated. Objective: To systematically investigate and quantify the effect of price change on dietary intake and on adiposity, as well as whether other underlying factors alter these effects. Methods: Using MOOSE and PRISMA guidelines, we systematically searched PubMed, Embase, EconLit, OVID, Cochrane library, Web of Knowledge, and CINHAL for prospective observational or interventional studies of price differences and diet (foods, drinks, energy) or adiposity. Studies were excluded if cross-sectional; price data collected before 1990; or reporting only crude risk estimates. Data were extracted independently and in duplicate. Findings were pooled using inverse-variance meta-analysis Results: From 2,299 identified abstracts, 21 met inclusions. These included 6 randomized trials and 7 quasi-experimental studies in different settings (supermarket, school/workplace cafeteria, restaurant) in 3 countries (US, New Zealand, Netherland); and 8 observational studies mostly using nationally representative US data. Studies evaluated effects of increase (n=10, 1-35% increase) in price (fast food, energy dense snacks, soda) and decrease (n=11, 10-50% decrease) in price (fruits, vegetables, low fat/calorie products) among adults (n=13) and children (n=8). Studies consistently showed that price increases led to decreased consumption; effects of price decreases on consumption and price increases/decreases on BMI were less consistent. A mean $0.43/serving (12 oz) increase in price of soda was associated with 2.77 servings/wk lower consumption (95% CI: 1.58. 3.96, n=4 studies). A mean %30/serving decrease in price of fruits and vegetables was not significantly associated with consumption (+536 g/d, 95% CI: -427, 1500, n=2 studies). High between study heterogeneity was evident for price increase and soda intake and price discount and fruit intake. Conclusions: These prospective results support taxation to reduce soda intake. More evidence from prospective studies and trials is needed on food pricing and other dietary outcomes and adiposity.