Thursday, May 21, 2015

Hunger & Satiety - Is it All Just in Our Heads? Psychology Looms Large and the Energy Content is Readily Overridden by the Texture and Thickness of Foods and Beverages

Hours before your gut even knows how much energy the stuff you ate actually contained, your brain guesstimates its satiety effects and... as you may expect... is quite easy to fool. In some cases with "bingy" consequences.
If you ask people about how to eat to increase your satiety, you will probably hear something like: "Dude, you gotta eat less carbohydrates and more protein!" or "Yo bro, you gotta eat a ketogenic diet with lots of da good fats!" How futile and potentially consequential the vilification of individual nutrients can be, becomes obvious if one analyses how consumer expectations modify responses to ingested nutrients.

As a SuppVersity reader you know that satiety is not an objectively predictable quantity. The degree of satiety we feel after a meal is influence by a complex integration of cognitive, sensory and post-ingestive signals which are generated by the consumed product and its interaction with the environment and out belief system.
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So, to fully understand what satiates us, one has to go beyond the stupid carbohydrate vs. protein vs. fat discussion and try to develop what Yeomans (2015) demands, i.e....
"[a] better understanding of how these different signals interact could allow the development of novel products optimised to produce satiety, thereby helping to counteract the effects of obesogenic lifestyles" (Jeomans. 2015).
In the latest paper in the Nutrition Bulletin the scientists reviews recent studies, conducted largely as part of the BBSRC DRINC initiative, which examined how beliefs about satiety before food ingestion and the sensory experience during ingestion together influence how the consumer responds to food. Examples? Well, here you go. The two most common effects are...
  • Sensory enhance satiety - Thicker drinks will be considered more satiating than thinner drinks; even if the thin drink had sign. more calories, the thick one did still produce the greater satiety expectation and (short term) satiety response.
    Figure 1: A high protein meal is only more satiating than a high carb meal, if it is also thicker (HP+: thick high protein, HC+: thick high carb, HP-: thin high protein meal | Bertenshaw. 2013)
    Even if protein is added, the satiety effect vanishes if this does not add to the texture of the product (Bertenshaw. 2013 | see Figure 1).
Artificial sweeteners have also been accused of cheating your body into the false belief that he was fed tons of energy and thus of triggering rebound hunger and binges. The reality looks very different, though | learn more.
Not all that's initially satiating is "gold" - beware of the rebound hunger! If the consumer’s experience of satiety is stronger when the post-ingestive effects of nutrient ingestion are predicted by the product’s sensory qualities, what happens if expectations of satiety are high but actual nutrient delivery is less than expected? Yes, they will feel more more hungry just prior to the testmeal, and crucially, studies also confirm that they will then consume more, than if they had consumed the same amount of energy without the expectation of satiety. As Yeomans points out this rebound hunger effect is usually explained by the downstream physiological effects that are generated by the expectations (e.g. an increased insulin release appropriate for a much larger meal | Smeets et al. 2010). If that's actually the case (scientists are still debating if this occurs chronically) the rebound hunger could turn "diet foods" into obesogens!
  • Cognitively-enhanced satiety - If something is thick or thin, this will obviously have both physical and cognitive effects on the satiety response, but that's nothing "learning" could not change. In fact, studies have repeatedly shown that the same effect can be achieved by changing expectations through cognitive approaches, such as product labelling and contextual information. There has been a marked increase in the number of products available to consumers that make explicit reference to their ability to counter post-ingestive hunger, with these claims based on the products’ ingredients (usually higher levels of protein and fibre).
    Table 1: It's all about finding the right words. Describing a drink / snack as refreshing or filling will influence the consumer's hunger and thirst response to the drink; these are the original product descriptors the subjects in the study by McCrickerd et al. were provided with (McCrickerd. 2014).
    A further study conducted as part of the BBSRC DRINC programme lends support to that argument (McCrickerd et al. 2014). Again, based on a pre-load design with covert energy manipulation, participants consumed the same low and high energy dairy-juice drinks used in previous studies, but rather than enhancing satiety expectations by manipulating sensory characteristics, the key manipulation was persuading the consumers that the product was either specially designed to suppress appetite or to assuage thirst.

    Whereas compensation for covert energy in the absence of satiety expectations was weak (6%), this increased to 35% when the products were consumed with the belief that they suppressed appetite. Although this cognitive effect was not as strong as a high as it was, when the sensory characteristics were manipulated 70% compensation), it clearly demonstrates that beliefs alone can enhance nutrient-derived satiety.
In view of the results presented in this SV article, it's hardly surprising that 4 scoops of protein are not sign. more satiating than one scoop | more
The results of these studies leave little room for a classic, mechanistic concept of satiety. Rather than that, they highlight the integrative nature of satiety and pave the way for updated models of satiety and novel products that should aid consumers' ability to regulate their appetite.

Whether simply knowing about the ability of label claims to modify the products effect on your response is enough to negate it, would actually be an important next step to do. After all, you as SuppVersity readers should be significantly less susceptible to the "placebo satiety" effect of satiety promoting "functional foods" than the average bro  | Comment on Facebook!
  • Bertenshaw, Emma J., Anne Lluch, and Martin R. Yeomans. "Perceived thickness and creaminess modulates the short-term satiating effects of high-protein drinks." British Journal of Nutrition 110.03 (2013): 578-586.
  • McCrickerd, Keri, Lucy Chambers, and Martin R. Yeomans. "Fluid or fuel? The context of consuming a beverage is important for satiety." PloS one 9.6 (2014): e100406.
  • Yeomans, M. R. "Cued satiety: How consumer expectations modify responses to ingested nutrients". Nutrition Bulletin, 40 (2015): 100–103. doi: 10.1111/nbu.12139