Portion size: review and framework for interventions

The prevalence of overweight and obesity has increased. A strong environmental factor contributing to the obesity epidemic is food portion size. This review of studies into the effects of portion size on energy intake shows that increased food portion sizes lead to increased energy intake levels. Important mechanisms explaining why larger portions are attractive and lead to higher intake levels are value for money and portion distortion. This review also shows that few intervention studies aiming to reverse the negative influence of portion size have been conducted thus far, and the ones that have been conducted show mixed effects. More intervention studies targeted at portion size are urgently needed. Opportunities for further interventions are identified and a framework for portion size interventions is proposed. Opportunities for intervention include those targeted at the individual as well as those targeted at the physical, economic, political and socio-cultural environment.

Introduction

Overweight and obesity are increasing problems in western societies. Environmental factors contribute to the obesity epidemic [1] by promoting energy intake and limiting opportunities for energy expenditure [2]. A strong environmental factor influencing energy intake is food portion size [3–6]. Although research on the actual development of portion sizes is limited, it is clear that portion sizes have increased over the past decades [7–11]. Studies have been conducted in the United States [7–10] and in Denmark [11]. These studies show that, since the 1970s, portion sizes of especially high energy-dense foods, eaten inside as well as outside the home, have increased. This accounts for both amorphous foods and foods served in units [9]. Fast-food restaurants, for example, have shown a trend over the last decades to supersize their portions, and have introduced large and mega meals [9–11]. Another example is the increased package sizes of products sold in supermarkets, such as sugar-sweetened beverages [11].

Food portions in the United States tend to be larger than in Europe. However, in Europe, portion sizes have also increased [5, 10, 11]. Increased portion sizes may lead to increased energy intake levels. Studies on interventions that aim to reverse this trend are scarce, and urgently needed. In this article, firstly we review the effects of portion size on energy intake, followed by possible explanations for this relationship. Next, we assess the currently available interventions and their effectiveness. To conclude, we identify further opportunities for interventions aimed at portion size and propose a framework for portion size interventions.

Methods

Search strategy

For this review, firstly we asked: What is the effect of portion size on energy intake? Secondly, we assessed the effects of currently available portion size interventions on food intake. Studies were identified using the PUBMED database, the Cochrane Library and the Web of Science (ISI). The following keywords were used for the first question: 'portion size'; 'energy intake'; 'food intake'; and 'food consumption'. For the second part, the keywords 'portion size'; 'intervention'; or 'programme' were used. Furthermore, studies were also identified based on references of the found articles.

Inclusion and exclusion criteria

Only studies with adults as research population were included in this review. However, intervention studies with a mixed study sample, but consisting mainly of adults, were also included. Studies with less than 20 subjects were excluded in all cases. Food intake had to be an outcome measure of the study to be included in the review. More specifically, food intake of the product whose portion size was manipulated had to be an outcome measure (for example, instead of only the food intake of a non-manipulated subsequent meal). In addition, for the second part, intervention studies that used food selection as an outcome measure were also included.

For the first question, studies varying only the package format and not the actual portion size were excluded (for example 30 grams in a small package versus 30 grams in a large package). Regarding study design, between subjects designs were included as well as within subjects cross-over designs for the first research question. Since studies into the effectiveness of interventions aimed at portion size are very scarce, no further requirements were defined regarding research design for the second question.

Portion size and energy intake

Do increased portion sizes lead to increased energy intake levels? Thirteen studies met the inclusion criteria and investigated this relationship, mostly using a within subject's cross-over design (see Table 1) [12–24]. The larger portion sizes used in the studies varied from 125% of the control portion to up to 500% the control portion, but most studies investigated portion sizes between the control size and twice the control size. All studies showed that people's energy intake increases when offered a larger portion. This also accounts for food with an unfavourable perceived taste, i.e. stale popcorn [23].

figure 1

Feasibility

The feasibility of interventions targeted at portion size depends on the willingness of both consumers and point-of-purchase settings to accept these interventions. A qualitative study into consumer attitudes about portion size interventions indicated that consumers had particularly favourable attitudes towards a larger variety of portion sizes and pricing strategies, followed by labelling interventions (March 2007; unpublished data). Another qualitative study using semi-structured individual interviews with representatives of point-of-purchase settings, showed that most interventions aimed at portion size can be considered as innovative. Nonetheless, offering a larger variety of portion sizes and portion-size labelling were perceived as especially feasible interventions [59]. Also, O'Dougherty et al [60] showed that a third of fast-food restaurant patrons favoured a law requiring restaurants to change their pricing strategies and offer lower prices for smaller portions, instead of more value for money for larger portions.

Conclusion

Portion sizes seem to have increased considerably over the last few decades. It is important to continue studying trends in actual portion size development, since not many studies are currently available. The same applies to studies into the long-term effects of increased portion sizes. This review summarizes the available evidence, demonstrating that increased portion sizes lead to increased energy intake levels. Important factors explaining why larger portions are attractive, and why they lead to higher intake levels, are related to value for money and portion distortion. Only few intervention studies have been conducted to target portion size. Interventions that have been tested were directed mainly towards the physical environment, namely portion size reduction and portion size labelling or information. So far, interventions have shown mixed effects. Intervention studies are urgently needed, to find out what type of interventions, targeted at portion size, are effective, in what setting, and among which target groups. These studies should focus on educational programmes, but also on interventions in the physical, economic, politic and socio-cultural environments.

References

  1. Swinburn B, Egger G, Raza F: Dissecting obesogenic environments: The development and application of a framework for identifying and prioritizingenvironmental iinterventions for obesity. Prev Med. 1999, 29: 563-570. 10.1006/pmed.1999.0585. ArticleCASGoogle Scholar
  2. Drewnowski A, Rolls BJ: How to modify the food environment. J Nutr. 2005, 135: 898-899. CASGoogle Scholar
  3. Giskes K, van Lenthe F, Brug J, Mackenbach JP, Turrell G: Socioeconomic inequalities in food purchasing: The contribution of respondent-perceived and actual (objectively measured) price and availability of foods. Prev Med. 2007, 45 (1): 41-8. 10.1016/j.ypmed.2007.04.007. ArticleCASGoogle Scholar
  4. Ledikwe JH, Ello-Martin JA, Rolls BJ: Portion sizes and the obesity epidemic. J Nutr. 2005, 135: 905-909. CASGoogle Scholar
  5. Rozin P, Kabnick K, Pete E, Fischler C, Shields C: The ecology of eating: Smaller portion sizes in France than in the United States help explain the French paradox. Psychol Sc. 2003, 14 (5): 450-454. 10.1111/1467-9280.02452. ArticleGoogle Scholar
  6. Swinburn BA, Caterson I, Seidell JC, James WPT: Diet, nutrition and the prevention of excess weight gain and obesity. Public Health Nutr. 2004, 7 (1A): 123-146. CASGoogle Scholar
  7. Nielsen SJ, Popkin BM: Patterns and trends in food portion sizes, 1977–1998. JAMA. 2003, 289 (4): 450-453. 10.1001/jama.289.4.450. ArticleGoogle Scholar
  8. Smiciklas-Wright H, Mitchell DC, Mickle SJ, Goldman JD, Cook A: Foods commonly eaten in the United States, 1989–1991 and 1994–1996: Are portion sizes changing?. J Am Diet Assoc. 2003, 103 (1): 41-47. 10.1053/jada.2003.50000. ArticleGoogle Scholar
  9. Young LR, Nestle M: The contribution of expanding portion sizes to the US obesity epidemic. Am J Public Health. 2002, 92 (2): 246-249. 10.2105/AJPH.92.2.246. ArticleGoogle Scholar
  10. Young LR, Nestle M: Portion sizes and obesity: Responses of fast-food companies. J Public Health Pol. 2007, 28: 238-248. 10.1057/palgrave.jphp.3200127. ArticleGoogle Scholar
  11. Matthiessen J, Fagt S, Biltoft-Jensen A, Beck AM, Ovesen L: Size makes a difference. Public Health Nutr. 2003, 6 (1): 65-72. 10.1079/PHN2002361. ArticleGoogle Scholar
  12. Dilliberti N, Bordi PL, Conklin MT, Roe LS, Rolls BJ: Increased portion size leads to increased energy intake in a restaurant meal. Obes Res. 2004, 12 (3): 562-568. 10.1038/oby.2004.64. ArticleGoogle Scholar
  13. Fisher JO, Arreola A, Birch LL, Rolls BJ: Portion size effects on daily energy intake in low-income Hispanic and African American children and their mothers. Am J Clin Nutr. 2007, 86: 1709-1716. CASGoogle Scholar
  14. Flood JE, Roe LS, Rolls BJ: The effects of increased beverage portion size on energy intake at a meal. J Am Diet Assoc. 2006, 106: 1984-1990. 10.1016/j.jada.2006.09.005. ArticleGoogle Scholar
  15. Kral TVE, Roe LS, Rolls BJ: Combined effects of energy density ad portion size on energy intake in women. Am J Clin Nutr. 2004, 79 (6): 962-968. CASGoogle Scholar
  16. Raynor HA, Wing RR: Package unit and amount of food: Do both influence intake?. Obesity. 2007, 15 (9): 2311-2319. 10.1038/oby.2007.274. ArticleGoogle Scholar
  17. Rolls BJ, Morris EL, Roe LS: Portion size of food affects energy intake in normal-weight and overweight men and women. Am J Clin Nutr. 2002, 76: 1207-1213. CASGoogle Scholar
  18. Rolls BJ, Roe LS, Kral TVE, Meengs JS, Wall DE: Increasing the portion size of a packaged snack increases energy intake in men and women. Appetite. 2004, 42: 63-69. 10.1016/S0195-6663(03)00117-X. ArticleGoogle Scholar
  19. Rolls BJ, Roe LS, Meengs JS, Wall DE: Increasing the portion size of a sandwich increases energy intake. J Am Diet Assoc. 2004, 104 (3): 367-372. 10.1016/j.jada.2003.12.013. ArticleGoogle Scholar
  20. Rolls BJ, Roe LS, Meengs JS: Larger portion sizes lead to sustained increase in energy intake over 2 days. J Am Diet Assoc. 2006, 106: 543-549. 10.1016/j.jada.2006.01.014. ArticleGoogle Scholar
  21. Rolls BJ, Roe LS, Meengs JS: The effect of large portion sizes on energy intake is sustained for 11 days. Obesity. 2007, 15 (6): 1535-1543. 10.1038/oby.2007.182. ArticleGoogle Scholar
  22. Wansink B, Park SB: At the movies: How external cues and perceived taste impact consumption volume. Food Qual Prefer. 2001, 12: 69-74. 10.1016/S0950-3293(00)00031-8. ArticleGoogle Scholar
  23. Wansink B, Kim J: Bad popcorn in big buckets: Portion size can influence intake as much as taste. J Nutr Educ Behav. 2005, 37: 242-245. 10.1016/S1499-4046(06)60278-9. ArticleGoogle Scholar
  24. Wansink B, Painter JE, North J: Bottomless bowls: Why visual cues of portion size may influence intake. Obesity Res. 2005, 13 (1): 93-100. 10.1038/oby.2005.12. ArticleGoogle Scholar
  25. French SA: Public health strategies for dietary change: Schools and workplaces. J Nutr. 2005, 135 (4): 910-912. CASGoogle Scholar
  26. Wansink B: Can package size accelerate usage volume?. J Marketing. 1996, 60: 1-14. 10.2307/1251838. ArticleGoogle Scholar
  27. Penisten M, Litchfield R: Nutrition education delivered at the state fair: Are your portions in proportion?. J Nutr Educ Behav. 2004, 36: 275-277. 10.1016/S1499-4046(06)60392-8. ArticleGoogle Scholar
  28. Schwartz J, Byrd-Bredbenner C: Portion distortion: Typical portion sizes selected by young adults. J Am Diet Assoc. 2006, 106: 1412-1418. 10.1016/j.jada.2006.06.006. ArticleGoogle Scholar
  29. Bryant R, Dundes L: Portion distortion: A study of college students. J Consum Aff. 2005, 39 (2): 399-408. 10.1111/j.1745-6606.2005.00021.x. ArticleGoogle Scholar
  30. Young LR, Nestle M: Expanding portion sizes in the US marketplace: Implications for nutrition counselling. J Am Diet Assoc. 2003, 103 (2): 231-234. 10.1053/jada.2003.50027. ArticleGoogle Scholar
  31. Hogbin M, Hess M: Public confusion over food portions and servings. J Am Diet Assoc. 1999, 99 (10): 1209-1211. 10.1016/S0002-8223(99)00297-7. ArticleCASGoogle Scholar
  32. Burger K, Kern M, Coleman K: Characteristics of self-selected portion size in young adults. J Am Diet Assoc. 2007, 107: 611-618. 10.1016/j.jada.2007.01.006. ArticleGoogle Scholar
  33. Condrasky M, Ledikwe JH, Flood JE, Rolls BJ: Chefs' Opinions of Restaurant Portion Sizes. Obesity. 2007, 15 (8): 2086-2094. 10.1038/oby.2007.248. ArticleGoogle Scholar
  34. Young LR, Nestle M: Variation in perceptions of a "medium" food portion: Implications for dietary guidance. J Am Diet Assoc. 1998, 98 (4): 458-459. 10.1016/S0002-8223(98)00103-5. ArticleCASGoogle Scholar
  35. Geier AB, Rozin P, Doros G: A new heuristic that helps explain the effect of portion size on food Intake. Psychol Sci. 2006, 17 (6): 521-525. 10.1111/j.1467-9280.2006.01738.x. ArticleGoogle Scholar
  36. Wansink B: Environmental factors that increase the food intake and consumption volume of unknowing consumers. Annu Rev Nutr. 2004, 24: 455-479. 10.1146/annurev.nutr.24.012003.132140. ArticleCASGoogle Scholar
  37. Pelletier AL, Chang WW, Delzell JJ, McCall JW: Patients' understanding and use of snackfood package nutrition labels. JABFP. 2004, 17 (5): 319-323. ArticleGoogle Scholar
  38. van Ittersum K, Wansink B: Do Children Really Prefer Large Portions? Visual illusions bias their estimates and intake. J Am Diet Assoc. 2007, 107 (7): 1107-1110. 10.1016/j.jada.2007.05.020. ArticleGoogle Scholar
  39. Wansink B, van Ittersum K, Painter JE: Ice cream illusions. Bowls, spoons, and self-served portion sizes. Am J Prev Med. 2006, 31 (3): 240-243. 10.1016/j.amepre.2006.04.003. ArticleGoogle Scholar
  40. Wansink B, Cheney MM: Super bowls: Serving bowl size and food consumption. JAMA. 2005, 293 (14): 1727-1728. 10.1001/jama.293.14.1727. CASGoogle Scholar
  41. Rolls BJ, Roe LS, Halverson KH, Meengs JS: Using a smaller plate did not reduce energy intake at meals. Appetite. 2007, 49: 652-660. 10.1016/j.appet.2007.04.005. ArticleGoogle Scholar
  42. Blundell JE, Macdiarmid JI: Fat as a risk factor for overconsumption: Satiation, satiety, and patterns of eating. J Am Diet Assoc. 1997, 97S (suppl): S63-S69. 10.1016/S0002-8223(97)00733-5. ArticleGoogle Scholar
  43. Antonuk B, Block LG: The effect of single serving versus entire package nutritional information on consumption norms and actual consumption of a snack food. J Nutr Educ Behav. 2006, 38: 365-370. 10.1016/j.jneb.2006.05.016. ArticleGoogle Scholar
  44. Harnack LJ, French SA, Oakes JM, Story MT, Jeffery RW, Rydell SA: Effects of calorie labelling and value size pricing on fast food meal choices: Results from an experimental trial. IJBNPA. 2008, 5: 63. Google Scholar
  45. Lieux EM, Manning CK: Evening meals selected by college students: Impact of the foodservice system. J Am Diet Assoc. 1992, 92 (5): 560. CASGoogle Scholar
  46. Rolls BJ, Roe LS, Meengs JS: Reductions in portion size and energy density of foods are additive and lead to sustained decreases in energy intake. Am J Clin Nutr. 2006, 83: 11-17. CASGoogle Scholar
  47. Ueland O, Cardello AV, Merrill EP, Lesher LL: Effect of portion size information on food intake. J Am Diet Ass. 2009, 109 (1): 124-127. 10.1016/j.jada.2008.10.002. ArticleGoogle Scholar
  48. Ayala GX: An experimental evaluation of a group- versus computer-based intervention to improve food portion size estimation skills. Health Educ Res. 2006, 21 (1): 133-145. 10.1093/her/cyh049. ArticleGoogle Scholar
  49. Brown RM, Oler CH: A food display assignment and handling food models improves accuracy of college student's estimates of food portions. J Am Diet Assoc. 2000, 100 (9): 1063-1064. 10.1016/S0002-8223(00)00309-6. ArticleCASGoogle Scholar
  50. Camelon KM, Hadell K: The Plate Model: A visual method of teaching meal planning. J Am Diet Assoc. 1998, 98 (10): 1155-10.1016/S0002-8223(98)00267-3. ArticleCASGoogle Scholar
  51. Dagget LM, Rigdon KL: A computer-assisted instructional program for teaching portion size versus serving size. J Community Health Nurs. 2006, 23 (1): 29-35. 10.1207/s15327655jchn2301_3. ArticleGoogle Scholar
  52. Riley WT, Beasley J, Sowell A, Behar A: Effects of a web-based food portion training program on food portion estimation. J Nutr Educ Behav. 2007, 39: 70-76. 10.1016/j.jneb.2006.08.028. ArticleGoogle Scholar
  53. Rolls BJ: The supersizing of America. Nutr Today. 2003, 38 (2): 42-53. 10.1097/00017285-200303000-00004. ArticleGoogle Scholar
  54. Ello-Martin JA, Ledikwe JH, Rolls BJ: The influence of food portion size and energy density on energy intake: implications for weight management. Am J Clin Nutr. 2005, 82 (sSuppl): S236-S241. Google Scholar
  55. Brug J, van Lenthe F: Environmental determinants and interventions for physical activity, nutrition and smoking: A review. 2005, Rotterdam: ErasmusMC Google Scholar
  56. Osterholt KM, Roe LS, Rolls BJ: Incorporation of air into a snack food reduces energy intake. Appetite. 2007, 48: 351-358. 10.1016/j.appet.2006.10.007. ArticleGoogle Scholar
  57. Young LR, Nestle MS: Portion sizes in dietary assessment: issues and policy implications. Nutr Rev. 1995, 53 (6): 149-158. ArticleCASGoogle Scholar
  58. Hartstein J, Cullen KW, Reynolds KD, Harrell J, Resnicow K, Kennel P: Impact of portion-size control for school a la carte items: changes in kilocalories and macronutrients purchased by middle school students. J Am Diet Assoc. 2008, 108: 140-144. 10.1016/j.jada.2007.10.005. ArticleGoogle Scholar
  59. Vermeer WM, Steenhuis IHM, Seidell JC: From the point-of-purchase perspective: A qualitative study of the feasibility of interventions aimed at portion-size. Health Policy. 2009, 90 (1): 73-80. 10.1016/j.healthpol.2008.07.006. ArticleGoogle Scholar
  60. O'Dougherty M, Harnack LJ, French SA, Story M, Oakes JM, Jeffery RW: Nutrition labelling and value size pricing at fast-food restaurants: A consumer perspective. Am J Health Promot. 2006, 20 (4): 247-250. ArticleGoogle Scholar

Acknowledgements

The authors wish to thank Franca Leeuwis for her contribution to this study.