INDICADORES DE GESTIÓN

As outlined in section 1.2.1.1 and 1.2.1.3, a potential consequence of learning is that people then hold explicit expectations about the satiating consequences of different foods, which can influence food choice and the development of satiety. It is possible that beverages may not be explicitly expected to be as satiating as other ‘foods’ (Mattes, 2005), but as yet this has not been explicitly tested.

Figure 1.2 An expected satiation task used in Hardman, McCrickerd and Brunstrom (2011): participants select the portion of pasta and sauce (comparison food) they think would make them feel equally as full as the ‘cheese string’ (target food). The larger the portion of pasta sauce selected (kcal), the more satiating the target food is expected to be and vice versa.

Brunstrom and colleagues (Brunstrom et al., 2008; Brunstrom & Shakeshaft, 2009) have developed a computerised task to quantify the expectations people hold about the satiating effect of foods (see Figure 1.2 for an example). This requires participants to indicate the anticipated satiating effect of a target food with a known energy content compared, calorie for calorie, to a comparison food (Brunstrom et al., 2008; Brunstrom

& Shakeshaft, 2009; Hardman et al., 2011). In their studies both adults and children demonstrated that they were able to select how much of a familiar comparison food, such as pasta and tomato sauce, they thought they would need to eat to feel equally as full (expected satiation) and/or to suppress hunger to the same extent (expected satiety) as a known portion of a target food. As highlighted in section 1.2.1.1, expectations of satiation and satiety are thought to depend on our previous experience: foods that are rated as more familiar (Brunstrom et al., 2010b; Brunstrom et al., 2008; Hardman et al., 2011) and/or have been previously consumed to fullness (Ferriday et al., 2011; Irvine et al., 2013), are expected to be more satiating. Brunstrom and colleagues argue this is because people have learned about the satiating effect of more familiar foods.

However, controlled laboratory studies do not provide conclusive evidence that specific expectations about the satiety value of a food can be easily changed with repeated exposure (Hogenkamp, Brunstrom, Stafleu, Mars, & de Graaf, 2012a; Wilkinson &

Brunstrom, 2009; Yeomans et al., 2014). Furthermore, in one study Irvine, Brunstrom, Gee and Rodgers (2013) measured the expected satiety value of a novel food, sushi, and although participants who were not familiar with this food judged it to be less satiating than those who were, they could still make a judgement. This suggests that

expectations of satiety are based on more than product-specific familiarity, and perhaps there are more general features of a food that can drive these beliefs.

Emerging evidence indicates that the extent to which a food is expected to be satiating is linked to its physical characteristics. Commercially available dessert products (custards and yogurts) perceived to be thicker (Hogenkamp et al., 2011) or heavier (Piqueras-Fiszman & Spence, 2012) were expected to be more filling than similar products that were less thick or heavy. Moreover, chewy and salty savoury foods were also expected to be more filling than less chewy and salty foods (Forde, van Kuijk, Thaler, de Graaf, & Martin, 2013). This suggests that if beverages are not expected to be particularly satiating, altering their sensory context to be more in-line with these cues that are associated with satiety could be an important way to enhance their anticipated satiating effect.

Is enhancing the anticipated satiating effect of a beverage likely to impact its actual satiating power post-consumption? Brunstrom et al. (2011) demonstrated that participants who expected a smoothie to be more satiating (because they believed it contained a large portion of fruit) experienced the smoothie as more filling over a 4 hour period post-consumption, compared to participants who believed the smoothie contained a small portion of fruit and expected it to be less filling. In a more elaborate study, researchers investigated the effect of expectations on satiety by successfully convincing participants that they would be consuming cherry-flavoured liquids and jellies that had the ability to either be solid or liquid in their stomach (Cassady et al., 2012). The researchers achieved this by showing participants a video where the products were shown to either liquefy or solidify in the presence of pretend ‘gastric acid’. Participants consumed both the beverage and jelly on two occasions, once believing it would be liquid in the stomach and another time that it would be a solid.

Consequently, both the sensory experience and the beliefs about their post-ingestive effects contributed to satiety responses: consuming the cherry liquid was associated with faster gastric emptying and gastrointestinal transit times, a smaller decline in

ghrelin and reduced insulin and GLP-1 release relative to consuming the oral-solid jellies. However, the beliefs about consumption most strongly influenced appetite sensations and later intake, with participants consuming less at a test meal four hours later and feeling less hungry and more full in this time than when they believed the product was solid rather than liquid in their stomach. There was also some evidence that expecting the product to be solid in the stomach slowed gastrointestinal transit times.

These findings, particularly those from Cassady et al. (2012), suggest that manipulating a person’s beliefs about the effect a beverage will have on satiety-related sensations can enhance the actual experience of satiety and even physiological responses to nutrients, at least in the short term. However, for real-world beverage products food companies and governments cannot lie to consumers about the ingredients in a product or tell them it will turn to solid in their stomach when in reality it will not. Thus, more realistic ways of improving the anticipated satiating effect of a beverage need to be considered.