Background: Addressing food portion sizes is a key untapped opportunity to help tackle obesity. This study sought to inform the agenda of a national movement involving diverse sectors to manage portion sizes in packaged foods, restaurants, cafeterias and prepared foods in grocery stores.
Methods: A Delphi study was conducted with representatives from public health, private-sector food companies and academia that formed a panel of experts (n = 32). Three iterative rounds of surveys were administered over 3 months. The surveys gathered opinions on psychological mindsets affecting portion size choice, eating habits, portion perception and distortion, passive overconsumption and challenges and advantages of this tool to improve population nutrition. The survey also inquired about visions for a future food environment. After every round, responses were analysed and questions narrowed to reach group consensus on specific items in the subsequent round.
Results: Although many experts fear that portion size interventions might be perceived as paternalistic, 91% of respondents agreed stealth interventions were preferable. Seventy-three per cent of experts believed that the most impactful portion size intervention was product reformulation while smaller packages were the most effective intervention according to only 28% of experts. The majority of the panel (59%) also believed that creating an artificial stopping point in packages was the best strategy to reduce food consumption. Finally, the study found that one of the most complex aspects of establishing a multi-sector collaboration for obesity prevention was to ascertain trust in the private sector's ability to balance profit versus social responsibility.[Corrections added on 21 March 2019, after first online publication: The percentage of experts who believed that small packages were the most effective intervention has been changed from "16%" to "28%".].
Conclusion: This study informs the agenda of a cross-sectoral, coordinated movement to tackle obesity through a combination of changing social norms, individual behaviours and industry practices around portion size. Although cross-sectoral collaboration for non-communicable disease prevention is encouraged by different organizations, strategic efforts to define a common agenda on portion size have been limited thus far. This research highlights important strategies in portion size interventions and steps needed for the success of such a movement, as part of a wider effort across sectors and stakeholders to halt and reverse obesity rates in the USA.
Keywords: Delphi survey; nutrition; portion size; public–private partnership.