Suggested portion sizes do not reflect actual portion size consumed

New study published: Comparing consumed portion sizes of energy dense foods with their on-pack serving sizes

In the last 20 years UK guidance on portion size has not been updated, despite larger portion sizes being consumed. A recent study, led by the Nutritional Epidemiology Group at the University of Leeds funded by the World Health Organisation, looked at the differences between suggested serving-sizes displayed on-pack and consumed portion sizes for energy-dense snack foods.

Product information for 13,313 energy-dense snack food products from 6 major UK retailers and manufacturers was used to determine pack-size and serving-size. These data were then compared to the consumed portion size for corresponding foods using data from the UK National Diet and Nutrition Survey (NDNS)*.

(Note: in this article pack-size refers to the weight for the entire pack. Serving-size refers to the weight shown on-pack as the suggested amount to consume per person on one occasion.)

Food items were split into 4 main groups: ‘Cakes’, ‘Biscuits’, ‘Chocolate’ and ‘Crisps’; within each group, foods were organised into subgroups e.g. within the main food group ‘Cakes’ there were 15 subgroups including: ‘Pastries’, ‘Fruit Pie’ and Doughnut’. ‘Biscuits’ contained 10 subgroups, ‘Chocolate’ was made up of 12 subgroups and ‘Crisps’ entailed 8 subgroups.

Consumed portion-size from the NDNS

The group with the highest mean consumed portion size was ‘Cakes’ (71g) and within this, ‘Pastries’ (106g), ‘Fruit Pie (inc mince)’ (96g), ‘Doughnut’ (76g) and ‘Eclairs’ (76g) had the highest mean consumed portion size. For ‘Crisps’, ‘Chocolate’ and ‘Biscuits’ the mean consumed portion sizes were: 45g, 40g and 33g, respectively.

On-pack serving-size

Many of the products analysed by this study (43%) did not have on-pack serving-size information, demonstrating the large number of energy-dense items that do not offer this guidance to consumers. This was particularly lacking in ‘Chocolate’ products, where only 35% products showed this information compared to 79%, 77% and 50% ‘Crisps’, ‘Cakes’, and ‘Biscuits’ products, respectively. For those products that did show on-pack serving size, the range varied greatly and was most pronounced within ‘Biscuits’.

The large number of products not displaying guidance on serving-size is particularly worrying; consumers may instead turn to the pack-size as a guide for unit of consumption, potentially leading to excess energy intake. However, the solution is complex; reducing the pack-size of food items to limit consumed portion size may instead push consumers into eating multiple items to compensate for the smaller size, thereby increasing intakes further.

Consumed portion-size vs. on-pack serving-size

The study found that for ‘Crisps’ the mean consumed portion-size was 44% larger than the mean on-pack serving size, equating to an extra 69kcal, 3.8g fat and 0.2 g salt per serving. Within ‘Crisps’, ‘Popcorn’ had the largest difference between consumed portion size and on-pack serving size (151% greater), adding an extra 240kcal, 11g sugar, 10.2g fat and 0.48g salt per serving. For ‘Biscuits’, ‘Chocolate’ and ‘Cakes’ the mean consumed portion-size was 27%, 26% and 16% larger than the mean on-pack serving size, respectively.

Interestingly the group ‘Crisps’ had the highest percentage of products displaying on-pack serving-size (79%) yet, this was also the group that had the largest difference between on-pack serving size and consumed portion-size. This could be explained by crisps often being sold in multipacks and larger ‘sharer’ packs, giving greater opportunity for over-consumption, the ‘sharer’ packs also often offer little practical serving size guidance. 

The front-of-pack labelling system currently encouraged in the UK displays nutrient information per serve. However, this study highlights that on-pack serving size is not representative of what individuals actually consume, perhaps leading to consumers to underestimate their nutritional intake. There is a fine balance to be struck in creating realistic, consistent serving-size guidance without encouraging consumers to eat larger portions or multiple units, particularly as consumers may not be using on-pack serving-sizes to guide their intake.


It’s clear that this is a deeply complex matter that needs to be considered from multiple angles in order to prevent further overconsumption.

This study provides a meaningful assessment of consumed portion size patterns in relation to on-pack serving sizes and could be used to help build policy and updated portion size guidance to support a healthy food and drink environment.

“This research shows the importance of providing on-pack serving size information that people can use to guide appropriate portion sizes. We need more information and a coherent policy focus to optimise  on-pack serving sizes in all product categories to help individuals consume smaller portions.” – Holly Rippin, University of Leeds – lead author of the study. 

(Note: *On-pack serving size information was taken from data obtained in 2013. Consumed portion size information was taken from the National Diet and Nutrition Survey Rolling Programme years 1-6 (2008-2014).)

Results of this study have been published and can be accessed here: 

For more information on the study please contact the corresponding author: Holly Rippin

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