Manipulating portion sizes may not solve obesity epidemic

Reducing portion size may not be the answer to reducing overall energy intake, a new review, conducted by a Swansea University professor, has found.

The UK Public Health Responsibility Deal has called for reduced portion sizes as a way of reducing the nation’s caloric intakes, but the review, conducted by Professor David Benton, found that consumers make their decisions on food consumption based on a number of different factors - with nutrition coming some way down the list of priorities.

To date, the evidence of consumer behaviour - outside the controlled laboratory environment - is unable to determine the extent to which portion size of prepared food and beverages is a major contributor to daily energy intake. In the real world (ie, the supermarket), there are a multitude of competing issues that impact what a consumer purchases and ultimately eats.

A range of factors will influence the size of the portion size chosen, such as packaging, labelling, advertising and the unit size, rather than the portion size of the food item. The way portion size interacts with the multitude of factors that determine food intake needs to be established, Professor Benton says.

“In particular, the role of portion size in energy intake should be examined, as many confounding variables exist and we must be clear that it is portion size that is the major problem,” Professor Benton wrote in the review abstract. “This may prove to be a problem in a free market, as it is to be expected that customers will resist the introduction of smaller portion sizes, given that value for money is an important motivator.

“Obesity reflects the outcome of many factors, such that concerns about portion size need to be part of a multifaceted approach to the topic,” Professor Benton said. “It is unlikely that any single change is going to have a significant impact; rather, there is a need for a coordinated approach that addresses a range of factors that deal with both energy intake and energy expenditure.”

The review is published online in Critical Reviews in Food Science and Nutrition.