Reducing portion size - how low can we go?

Campden BRI’s product development lead analyses how much portion sizes can be reduced before the consumer begins to reject the product.

13 February 2020

Meet the Expert

Who: Sarah Chapman

What: Product Development Lead

Where: Campden BRI


Whether it’s due to eating too much or moving too little, obesity is becoming a growing problem in the UK. Regardless of who is responsible (the industry or the consumer), the bottom line is simple: the number of calories the average person consumes must be reduced. 

To achieve this, in 2017 Public Health England (PHE) urged manufacturers to reduce the sugar in their products by 20% - including biscuits, cakes, sweet confectioneries and breakfast cereals - by 2020. The following year PHE published voluntary guidelines challenging the food industry to reduce calories by 20% by 2024 for food categories that included pizzas, ready meals, snack products, ready-made sandwiches and other “on the go” foods.

On the road to reduction

To help the food industry with this task, PHE suggests three ways of reducing calories. However, each carries its own challenges:

  • Reducing portion size – what’s to say consumers won’t eat two portions or reject the product?
  • Encouraging consumers to purchase lower calorie products – how effective will this be?
  • Changing the product’s recipe – what will the calories be replaced with?

Research into reducing portion size

Previous research has found that when we’re offered larger-sized portions, packages (e.g. big crisp packets) or tableware (e.g. large plates), the amount of food - and therefore the calories we consume - ultimately increases.  With this in mind, reducing portion size appears to be a promising way of reducing the public’s calorie intake.   

At Campden BRI we have been looking at cake bar portions; specifically, how much we can reduce the portion size until the consumer begins to reject the product.   

The investigation presented 136 consumers with eight cake bars ranging in size from 58g down to 23g. All variables were considered to ensure the product represented, as closely as possible, a genuine cake bar product - even down to designing mock packaging that mimicked what you would find in the supermarket. To understand the relationship between portion size reduction and consumer acceptance of the product, we used survival analysis: a data capture and analysis approach that, in this case, determines when a significant number of consumers begin to reject a product.

What did we find?

Overall, our research suggests that it is possible to make a 35% reduction in the size of a 58g cake bar with the product remaining acceptable to 80% of consumers. In practical terms, this would result in a reduction of 91 kcal and 5.9 g of sugar per bar. 

What this means for the industry

Alongside the results, we also proved that using a survival analysis approach with consumer data is a powerful way for food manufacturers to determine how much they can reduce their products’ portion sizes before consumers begin to reject them. 

Next, we will investigate the use of novel fibres and sweetness boosting natural flavours as a possible approach toward sugar reduction.

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