Too much variety may be fuelling the obesity crisis

By Niamh Michail

- Last updated on GMT

Reformulation to reduce fat, salt and sugar for some brands but not others means that consumers cannot rely on smell or taste as reliable predictors of energy content
Reformulation to reduce fat, salt and sugar for some brands but not others means that consumers cannot rely on smell or taste as reliable predictors of energy content

Related tags Food Obesity

Big differences in the calorie content for one food type distorts expectations of satiety and energy content leading to overeating - a feature of Western diets that is fuelling the obesity crisis, say researchers.

Offering consumers low-fat or sugar-free versions of foods  typically considered to be unhealthy has been seen as a way of fighting the obesity crisis while maintaining consumer choice and satisfying taste preferences.

But researchers from the University of Liverpool have found that having many brands to choose from, as well as high levels of caloric variability within the category, could in fact be a risk factor for overeating and obesity.

Variability led to confusion over the food’s satiating properties - meaning some consumers sought to minimise the ‘risk’ of feeling hungry afterwards by overeating, a process known as loss aversion.

The researchers claimed their findings brought a new understanding to the obesity epidemic, as previous studies have focussed on portion sizes and energy-dense foods.

For the first time, these findings highlight a process by which dietary variability may compromise food-intake control in humans," ​they wrote.

Lead researcher Charlotte Hardman said: “We found that people who ate a wide range of different brands and types of pepperoni pizza were more likely to carry on eating more, and were more likely to think the pizza was less filling.

“It would appear that this high variability of food items makes it more difficult for people to learn about food and manage their consumption which exposes a new feature of Western diets and which has potential public health implications.“

The study involved 199 subjects and looked at satiety expectations and caloric consumption of pepperoni pizza – a category typified by numerous brands and high degrees of variability in the energy content provided.

Of the 71 types of pepperoni pizza taken from across 14 brands, calorie values ranged from 501 to 1909 kcal - a 381% difference.

Reduced predictive powers

Because much of our dietary behaviour is based on prior experience, the oro-sensory properties of food – taste, smell and viscosity – are important in providing predictive clues as to its nutritional content and regulating food intake. 

But with huge variations within the energy content of processed food- without corresponding differences in taste - these predictive powers are no longer useful.

“It is possible that … dietary variability … [means] our ability to use the visual and oro-sensory properties of a specific food to anticipate its energy content is degraded. In this way, cues in pizza (e.g., sight, smell, taste) might no longer serve as reliable predictors of pizza energy content," ​they wrote.

This reduced ability was exacerbated for some participants:

"When loss averse participants were uncertain about the preload’s satiating capacity they tended to consume a larger test meal. This tendency may reflect a precautionary strategy (“playing it safe”) aimed at avoiding the potential negative effects of feeling hungry between meals."

The researchers also found higher levels of overeating amongst participants who reported eating higher energy-content pizzas in the past compared with those who tended to eat lower calorie pizzas, confirming that calorie compensation was governed by prior experience.

The study

199 participants completed an online survey giving details of the amount and types of pepperoni pizza they had eaten over the previous year, and completed a quiz which assessed how ‘loss averse’ they were.

A smaller sample of 66 individuals then took part on the laboratory stage. Subjects were given a preload meal (a quarter slice of Sainsbury’s pepperoni pizza, chosen for its average energy content) and were then told they could eat an ad libitum​ amount of the test meal (tortilla chips or chocolate cookies) until they felt comfortably full.

Participants rated their levels of hunger, fullness as well as expected and actual and the researchers measured the amount eaten. As predicted, participants who regularly ate different pizza brands tended to overeat the test meal, and to underestimate how full the pizza would leave them.

Hardman et al. have called for further research to determine a cause and effect relationship, as well as looking at different food categories -  in particular to determine whether the findings extend to consumption of low-energy sweeteners.


Source: PLOS One

Published: 29 April 2015, doi: 10.1371/journal.pone.0125869

So Many Brands and Varieties to Choose from: Does This Compromise the Control of Food Intake in Humans?”

Authors: C. A. Hardman, D. Ferriday et al.

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