Abstract
Meal variety has been shown to increase energy intake in humans by an average of 29%. Historically, research exploring the mechanism underlying this effect has focused on physiological and psychological processes that terminate a meal (e.g., sensory-specific satiety). We sought to explore whether meal variety stimulates intake by influencing pre-meal planning. We know that individuals use prior experience with a food to estimate the extent to which it will deliver fullness. These ‘expected satiation’ judgments may be straightforward when only one meal component needs to be considered, but it remains unclear how prospective satiation is estimated when a meal comprises multiple items. We hypothesised that people simplify the task by using a heuristic, or ‘cognitive shortcut.’ Specifically, as within-meal variety increases, expected satiation tends to be based on the perceived volume of food(s) rather than on prior experience. In each trial, participants (N = 68) were shown a plate of food with six buffet food items. Across trials the number of different foods varied in the range one to six. In separate tasks, the participants provided an estimate of their combined expected satiation and volume. When meal variety was high, judgments of perceived volume and expected satiation ‘converged.’ This is consistent with a common underlying response strategy. By contrast, the low variety meals produced dissociable responses, suggesting that judgments of expected satiation were not governed solely by perceived volume. This evidence for a ‘volume heuristic’ was especially clear in people who were less familiar with the meal items. Together, these results are important because they expose a novel process by which meal variety might increase food intake in humans.
Highlights
The ‘variety effect’ describes the increases in amount of food consumed when animals (Morrison, 1974; Rogers & Blundell, 1984; Rolls, Van Duijvenvoorde, & Rowe, 1983) and humans (Bellisle & Le Magnen, 1981; Rolls et al, 1981) are exposed to multiple foods with different sensory characteristics
We found a main effect of meal variety – participants matched a smaller quantity of rice as meal variety increased, F(3.8, 246.2) = 8.5, p < .001.1 Importantly, we observed a significant interaction between judgment type and level of meal variety, F(4.3, 281.5) = 11.5, p < .001.1 Fig. 2 illustrates this interaction
Effects of meal variety on judgments of expected satiation and perceived volume Across meals, participants matched a larger quantity of rice in the expected satiation than the perceived volume task, Moderating effects of familiarity
Summary
The ‘variety effect’ describes the increases in amount of food consumed when animals (Morrison, 1974; Rogers & Blundell, 1984; Rolls, Van Duijvenvoorde, & Rowe, 1983) and humans (Bellisle & Le Magnen, 1981; Rolls et al, 1981) are exposed to multiple foods with different sensory characteristics (taste, texture, odour, and appearance). The effects of food variety on energy intake are substantial and can occur both within a single meal and across meals (Remick, Polivy, & Pliner, 2009). In non-human animals, exposure to a variety of foods increases intake by roughly 25% (McCrory, Burke, & Roberts, 2012). In humans this figure is estimated at 29% (McCrory et al, 2012)
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