‘Portion size’ may not be a good way to curb obesity: Study

By Stephen Daniells

- Last updated on GMT

Related tags Portion size Nutrition

Nutritional labelling may mean more to consumers than portion sizes, according to a joint study from Norway and the US.

According to new findings published in the Journal of the American Dietetic Association, “the term portion size is not associated with ‘an appropriate amount to eat’ in the mind of the consumer”​.

With obesity levels on the increase globally, many initiatives to curb the rise have focussed on reducing the amount people eat. Indeed, the UK’s Food Standards Agency (FSA) has focussed on the topic and convened a workshop last year on the topic. The workshop followed a report that some products sold in the UK may have increased in size over the last 15-20 years.

The Food Standards Agency's focus on portion sizes is part of a programme of work in collaboration with the food industry on reformulation and other efforts to help people achieve a balanced diet.

But “information about portion size was not found to be a good tool to manipulate food-intake behaviour in this study. In addition, consumers’ interpretation of portion size was associated more with objective information about food than with the amount that would be appropriate to eat,”​ wrote lead author Oydis Ueland from Nofima Food in Norway.

“Implications are that consumers would benefit from a better understanding of actual macronutrient and caloric content of specific foods and diets,” ​added the authors.


Some confusion appears to surround the term, said Ueland and his co-workers, since it is used differently by food manufacturers, regulatory agencies, and consumers.

The researchers note that serving sizes used for US federal food-intake recommendations are the amounts for optimal nutrition, while the food industry defined the amount as ‘customarily consumed per eating occasion’.

Further confusion arises from the industry’s use of phrases such as ‘super-size’ and ‘healthy portion’, said the researchers.

“Understanding how consumers interpret the meaning of these terms would provide useful data for an overall strategy to regulate food intake.”

Filling in the gaps

In order to understand how consumers interpret the term, the researchers recruited 33 normal weight people, and randomised them to different lunch meals. The participants were served a lunch meal consisting of a set amount of pasta, described as 0.5, 1, or 1.5 portions, and then followed by ad libitum​ servings of the same pasta.

The researchers found that information about the portion size had no impact on measures of fullness or on how much participants ate altogether.

Indeed, a questionnaire found that the participants viewed the term ‘portion size’ to be a “standardised index of the nutritional content of a food/meal, rather than as an index by which to estimate personal food intake​”, wrote Ueland.

“Nutritional advisors should provide specific, objective information about portion sizes (eg, gram weights) when advising consumers, because the term portion size is not associated with ‘an appropriate amount to eat’ in the mind of the consumer,”​ concluded the researchers.

The other researchers were affiliated with US Army Natick Research and SAIC Inc.

Source: Journal of the American Dietetic Association​January 2009, Volume 109, Issue 1, Pages 124-127“Effect of Portion Size Information on Food Intake”​Authors: O. Ueland, A.V. Cardello, E.P. Merrill, L.L. Lesher

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