This rapid review is designed to identify, synthesise and interpret the latest evidence to provide a concise summary of the current state of knowledge. Commissioned by the Australian Government Department of Health and the Healthy Food Partnership Portion Size Working Group, the review addresses the question: “What is the effectiveness of potential portion size strategies for optimising portion sizes, and why are these effective (ineffective)?”
- This review identified six main types of portion size interventions reviewed in the literature: restricting amounts offered; changing dishware size; changing food labelling; product reformulation; changing unit pricing; and novel approaches, such as changing frequency of portions offered.
- Our major finding is that the compelling evidence that larger portion sizes of both five food group foods and discretionary food and drinks increase consumption is unmatched currently by specific evidence on how to reduce this effect.
- Eliminating larger portion sizes from the diet could reduce average daily energy consumed (estimated range from 12–16% among UK adults and 22–29% among US adults).
- Relatively few specific effective strategies to achieve this were identified, especially related to meals and snacks freely chosen in real-world settings, where a wide range of foods and drinks are available, or over a prolonged period.
- Effective strategies include: restricting portion size of discretionary foods and drinks in public sector settings, and adding portions of healthy low-energy dense foods (such as vegetables) to the first course to reduce energy intake in the second course.
- Potentially promising interventions with mixed results include: restricting portion size of discretionary choices in private sector settings; changing dishware size; and changing nutrition information labelling from single column (serving size only) to dual column (serving size and whole pack).
- Interventions that are not effective include: changing food labelling to provide comparison to a reference portion size; dividing foods into smaller portions and offering at different times and frequency; and those that reduce portion size of discretionary choices (fast food and drinks) without concomitant reduction in price (that is, non-linear unit price reductions).
- A combination of regulatory and non-regulatory measures is likely to be needed. Process evaluations of voluntary industry agreements to reduce portion size indicate ad hoc sign-up, suggesting mandatory agreements and/or regulation may be required. Impact and outcome evaluation of these agreements are lacking.
- Professor Amanda Lee, The Australian Prevention Partnership Centre
- Ms Meron Lewis, Research Assistant