Background Dietary energy density is thought to be a contributor to obesity, but the extent to which different magnitudes and types of reductions to food energy density decreases daily energy intake is unclear. The primary objective was to systematically review and meta-analyse experimental studies that have examined the effect that manipulating energy density of food has on total daily energy intake. Secondary objectives were to examine moderators of the effect that altering energy density has on daily energy intake and effects on body weight. Methods A systematic review and multi-level meta-analysis of studies on human participants that used an experimental design to manipulate the energy density of foods served and measured energy intake for a minimum of 1 day. Results Thirty-one eligible studies sampling both children (n = 4) and adults (n = 27) contributed 90 effects comparing the effect of higher vs. lower energy density of served food on daily energy intake to the primary meta-analysis. Lower energy density of food was associated with a large decrease in daily energy intake (SMD = − 1.002 [95% CI: − 0.745 to − 1.266]). Findings were consistent across studies that did vs. did not manipulate macronutrient content to vary energy density. The relation between decreasing energy density and daily energy intake tended to be strong and linear, whereby compensation for decreases to energy density of foods (i.e. by eating more at other meals) was minimal. Meta-analysis of (n = 5) studies indicated that serving lower energy dense food tended to be associated with greater weight loss than serving higher energy dense food, but this difference was not significant (− 0.7 kg difference in weight change, 95% CIs: − 1.34, 0.04). Conclusions Decreasing the energy density of food can substantially reduce daily energy intake and may therefore be an effective public health approach to reducing population level energy intake. Trial registration Registered on PROSPERO (CRD42020223973).

Portion sizes of many foods have increased over time. However, the size of effect that reducing food portion sizes has on daily energy intake and body weight is less clear. We used systematic review methodology to identify eligible articles that used an experimental design to manipulate portion size served to human participants and measured energy intake for a minimum of one day. Searches were conducted in September 2020 and again in October 2021. Fourteen eligible studies contributing 85 effects were included in the primary meta-analysis. There was a moderate-to-large reduction in daily energy intake when comparing smaller vs. larger portions (SMD = -.709 [95% CI: -.956 to -.461], ∼235kcal). Larger reductions to portion size resulted in larger decreases in daily energy intake. There was evidence of a curvilinear relationship between portion size and daily energy intake; reductions to daily energy intake were markedly smaller when reducing portion size from very large portions. In a subset of studies that measured body weight (4 studies contributing 5 comparisons), being served smaller vs. larger portions was associated with less weight gain (0.58kg). Reducing food portion sizes may be an effective population level strategy to prevent weight gain.

Background. Portion sizes of many foods have increased over time and reducing food portion sizes has been proposed as a public health strategy to reduce obesity. However, the extent to which reducing food portion sizes affects daily energy intake and body weight is unclear. Objective. To systematically review and meta-analyse experimental studies that have examined the effect that serving smaller vs. larger portion sizes has on total daily energy intake. Design. We used systematic review methodology to search identify eligible articles that used an experimental design to manipulate portion size served to human participants and measured energy intake for a minimum of one day. Multi-level meta-analysis was used to used to pool effects of portion size on daily energy intake. Results. Fourteen eligible studies were included and 85 effects were included in the primary meta-analysis. There was a moderate-to-large reduction in daily energy intake when comparing smaller vs. larger portions (SMD = -.709 [95% CI: -.956 to -.461], p < .001, I2 = 80.6%) and evidence of a dose dependent response. Larger reductions to portion size and reducing portion sizes of multiple meals per day both resulted in larger decreases in daily energy intake. There was also evidence of a curvilinear relationship between portion size and daily energy intake, whereby reductions to daily energy intake were markedly smaller when reducing portion size from very large portions. In a subset of studies that measured body weight (n=5), being served smaller portions was associated with less weight gain than larger portions (SMD = .536 ([95% CI: .268 to .803], p < .001, I2 = 47.0%). Conclusions. Smaller food portion sizes substantially decrease daily energy intake and there is evidence that over time this results in lower body weight. Reducing food portion sizes may be an effective population level strategy to reduce obesity.

Alcohol is calorie dense, but unlike food products, alcoholic drinks tend to be exempt from nutritional labelling laws that require energy content information to be displayed on packaging or at point of purchase. This review provides a perspective on the likely efficacy of alcoholic drink energy labelling as a public health policy to reduce obesity and discusses key questions to be addressed by future research. First, the contribution that alcohol makes to population level daily energy intake and obesity is outlined. Next, consumer need for alcohol energy labelling and the potential impacts on both consumer and industry behavior are discussed. Pathways and mechanisms by which energy labelling of alcoholic drinks could reduce obesity are considered, as well as possible unintended consequences of alcoholic drink energy labelling. Would widespread energy labelling of alcoholic drinks reduce obesity? The unclear effect that alcohol has on population level obesity, the modest contribution calories from alcohol make to daily energy intake and limited impact nutritional labelling policies tend to have on behavior, suggest alcohol energy labelling may have limited impact on population obesity prevalence as a standalone policy. However, there are a number of questions that will need to be answered by future research to make definitive conclusions on the potential for alcohol energy labelling policies to reduce obesity.

BackgroundDietary energy density is thought to be a contributor to obesity, but the extent to which different magnitudes and types of reductions to food energy density decreases daily energy intake is unclear.ObjectiveTo systematically review and meta-analyse experimental studies that have examined the effect that manipulating energy density of food has on total daily energy intake.DesignA systematic review and multi-level meta-analysis of studies on human participants that used an experimental design to manipulate the energy density of foods served and measured energy intake for a minimum of one day.ResultsThirty-one eligible studies contributed 90 effects comparing the effect of higher vs. lower energy density of served food on daily energy intake to the primary meta-analysis. Lower energy density of food was associated with a large decrease in daily energy intake (SMD = -1.002 [95% CI: -0.745 to -1.266]). Findings were consistent across studies that did vs. did not manipulate macronutrient content to vary energy density. The relation between decreasing energy density and daily energy intake tended to be strong and linear, whereby compensation for decreases to energy density of foods (i.e. by eating more at other meals) was minimal. Meta-analysis of (n=5) studies indicated that serving lower energy dense food tended to be associated with greater weight loss than serving higher energy dense food, but this difference was not significant (−0.7kg, 95% CIs: -1.34, 0.04).ConclusionsDecreasing the energy density of food can substantially reduce daily energy intake and may therefore be an effective public health approach to reducing population level energy intake.