Choosing & Processing Foods for Satiety: The Science 101 for Regular Consumers and Food Industry Insiders

Don't worry, this is no article about "Frankenfood" like salami bananas, ...

According to the drugs.com definition, a "designer food" is "a dietary supplements or foodstuffs containing nutrients and various combinations of vitamins, minerals, and other substances considered by some to offer clinically significant benefit, often without adequate scientific proof of efficacy." If you don't want your designer foods (or your self-prepared foods and meals) to fall into the latter category of products without adequate scientific proof of efficacy, this article is for you, because it summarizes the science on an often overlooked quality of food: its structure, and the effect the latter will have on your and/or customers' satiety.

Learn more about the satiety effects of foods, supplements and exercise

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More Protein Doesn't Always More Satiety

Fluids and solids - What's More Satiating?

Tryptophan, the Satiety Amino Acid?

Always Hungry? What's Triggering Your Craving?

In a recent review, Campbell et al. have aptly illustrated how both the product and the way(s) costumers eat it affect the individual satiety (see Figure 1).

Figure 1: Satiety is more complex than calories in vs. calories out - In fact, it's hardly about calories at all.

Allegedly, the separate roles of the initial food structure, structural transformations, oral processing,
and dynamic sensory perception in satiation (makes you stop eating) and satiety (reduces your incentive to have another meal | see blue box) have not been fully established, but hey: you've got to start somewhere when designing functional (satiating and satiety promoting) foods is #1 on your private or professional agenda. So here's what we know:

• food structure and texture contribute to satiation and satiety,
• time required for oral processing has been shown to influence satiation/satiety,

If we were able to integrate the interaction of food structure, texture, and oral processing on satiation/satiety this may help us to produce more satiating foods and thus help people lose weight. So how can we do that?  Vliet, van Aken, de Jongh, & Hamer (2009) classified foods as fitting into broad categories of:

1. fluids - fluids flow and have minimal or no yield stress (e.g. beverages like sodas or milk); 
2. semi-solids - semisolids are fluid-like, have a high yield stress, and deform or break without fracturing into pieces (e.g., pudding, yogurt, and bananas); 
3. soft solids - soft solids fracture into pieces but without sound (e.g., cooked egg white, some cheese and processed meats); and 
4. hard solids - hard solids fracture into pieces and emit sound during fracture (e.g., crackers, toast, nuts, apples, and carrots). 

Needless to say that these overall physical properties are (a) a result of the foods individual food structure and can (b) be modified to a certain degree and thus affect an individual food's satiety effect by either natural (e.g. fermentation, mixing, etc.) or artificial (e.g. enzymatic treatments, adding thickening agents, etc.) means.

But isn't that overrating the importance of texture?

Not really... After all, you must take into consideration that the texture of your foods will influence their satiating effect and your satiety (after the meal) by at least mechanisms, i.e.

• oral processing parameters which are directly influenced, as well as adjusted to accommodate changes in food texture throughout the chewing sequence and ...
• texture perception, which will influence your expectations of satiety, which - despite being a highly dynamic process that correlates with oral processing (chewing, etc.) will eventually have significant effects on the satiating and satiety effects of the foods you eat.

By turning a protein shake into a pudding with xanthan, for example, you will "force" yourself or your customers to consume the shake like a pudding: with a spoon. In addition, the mouthfeel of a pudding will leave them with the expectation that the product is more satiating than a watery whey protein shake - an expectation that usually turns into a self-fulfilling prophecy.

Table 1: Overview of the results of Campbell's review (2016); studies accompanied by a plus symbol (+) indicate that at least one measured marker of satiation/satiety was affected by texture

As Campbell et al. point out in their previously cited review, this has been shown in multiple study. Agrawal et al. (1998), for example, were one of the first to demonstrate the dependence of oral processing and thus your eating speed on intrinsic properties of food texture:

"Using a selection of cheeses, nuts, and carrots, the authors established a clear dependence of breakdown rate and activity of closing muscles on mechanical parameters – in this case, toughness and modulus of elasticity. More recent studies have expanded on this concept by utilizing a wider variety of foods varying in texture from fluids to soft and hard solids (Forde et al., 2013; Viskaal-van Dongen, Kok, & de Graaf, 2011). Though the foods were not characterized structurally, both Forde et al. (2013) and Viskaal-van Dongen et al. (2011) found significant differences in eating rates, ranging between 4 g/min for crisp foods such as rice cakes or tortilla chips, 100 g/min for soft cooked vegetables, and 650 g/min for thin beverages such as juice or soda. The total number of chews necessary to process 50 g samples ranged from 27 to 488 chews for mashed potatoes and tortilla chips, respectively while total oral processing time ranged from 27 s for canned tomatoes to 350 s for tortilla chips" (Cambell. 2016).

Now, I am probably not telling you something new, when I inform you that science shows that faster eating rates are associated with increased food intake. Thus the "real-world, real-food approach" (Campbell. 2016) indicates that foods requiring limited oral processing actions, such as liquids, semisolids, and soft, cooked solids, may be more easily over-consumed than hard or chewy solids, such as crackers, chips, or certain meats.

With its satiety-promoting effects soluble fiber will reduce the number of meals and prolong the intervals between meals on an ad-libitum diet. It will, however, not affect the satiating effect of an individual meal; meaning: if you are a binge eater whose extra body  fat is "acquired" from super-size meals, it's not going to get you lean.

Did you know that there's a difference between satiety and satiation? Satiety is what determines when and whether you're going to eat. Satiation is what tells your body that you can stop eating now.

Why would you care? Well, the answer can be found in a recent study on soluble fiber intakes, for example. While the latter will increase your satiety and thus reduce your meal frequency and the number of meals you will be consuming on an ad-libitum (eat when and how much you want), it won't affect your satiation. Practically speaking this means: Increasing the soluble fiber content of your diet is not going to magically prevent obesogenic binges - and, when all is said and done, 3x2000 kcal are as fattening as 6x1000kcal.

That doesn't sound so indisputable any longer, right? I mean we know that chips are not exactly more satiating than, say, chicken breasts. In this context, it is important to understand that pertinent studies measure eating rate by weight (g/min) rather than by total calorie intake (calories/minute). In our example, the chicken breast will yield higher eating speeds indicating that a higher amount (as in weight) of the product is being consumed per minute, but for a given amount of food, the caloric content of the chicken breasts is usually still significantly lower than that of potato chips, which is yet another example of the fact that you have to consider all variables (in this case, first and foremost texture, eating speed and relative energy density) and their interaction to predict the satiety and satiating effects of a meal.

But there's more to it than the difference between hard, soft and liquid. Even if you don't go beyond the structure (e.g. looking at the protein content of foods), modifying the microstructure with gelling protein-polysaccharides or reducing the creaminess by cutting down on fat will sign. affect the chewing rate and thus - at least theoretically - make foods more or less satiating.

So far so bad, because it's all theory!

I am not sure if you've tried low-fat cheese; but if you have, you will have notice that it chews and, unfortunately, tastes like cardboard and is thus hardly more satiating than regular cheese. To actually make reliable predictions about the satiating and satiety effect of various foods, it does, therefore, take real-world studies the design of which usually look as described by Campbell et al., recently:

" Measurements of satiation and satiety typically fall into three categories: subjective panelist ratings, physiological measurements, and ad libitum intake. Subjective panelist ratings of hunger and fullness, often in the form of a 100 mm visual analog scale (VAS), represent the most direct and simplistic measurement of hunger and fullness. These ratings are often corroborated by offering an ad libitum snack or meal and measuring how many calories the panelist consumes following consumption of a test food. One can also measure physiological biomarkers associated with metabolism, satiation, and satiety, including glucose, insulin, ghrelin, leptin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and gastric inhibitory peptide (de Graaf et al., 2004). Other physiological measurements include diet induced thermogenesis (Crovetti, Porrini, Santangelo, & Tesolin, 1997; Westerterp-Plantenga, Rolland, Wilson & Westerterp, 1999) and gastric emptying time (Blundell et al. 2010). While quantification of biomarkers provides an unbiased, physiological response, healthy panelists often exhibit wide ranges of biomarker concentrations and this biological variation can complicate interpretation of results. Combinations of the above measurements are more commonly utilized to account for biological and psychological variability" (Campbell. 2016).

From these studies, scientists have learned a lot. Not all of it was surprising. After all, we all have some knowledge of what is satiating and what is not. It is thus not a surprise that...

• protein is the most satiating macronutrient, carbohydrates come in as a distant second and fats are really trailing behind;

Table 2: Dietary fibre content of foods in commonly served portions (Slavin .1987).

• non-digestible carbohydrates are satiating, too  -  fiber (see Table 2) and resistant starches both fall into this category and are (rightly so) on the list of 'best-known satiety promoters'

That the satiating effect of protein is more or less independent of whether it is fast- or slow-digesting, on the other hand (see my recent article on whey and casein | read it), is something only a few people know. The same goes for the advantages of fiber with a high intrinsic viscosity – such as pectin, β-glucan, psyllium, guar gum, and alginate, which have been shown to have superior effects on individual's energy intake(s). Likewise on the list of often-overlooked satiety factors are...

• polyphenolic compounds - these plant molecules have been shown to form high affinity, non-covalent bonds with both food proteins and digestive enzyme, will thus slow digestion and nutrient absorption... and thus up the satiety effect of the product and/or limit the nutrient uptake from the foods (e.g. tannins in cocoa, fruits, tea, cinnamon, and peanuts have been shown to be 'carb blockers')

Figure 3: Even for high protein foods, turning a solid into a liquid significantly compromises its satiety effect as measured by the dietary energy consumed after an isocaloric protein preload in 40 obese & lean subjects (Mourao. 2016).

• grinding or homogenizing food - while solidifying is a tried and proven method to make a food more satiating, grinding, pureeing, homogenizing and co will decrease the satiety effects of foods such as a chunky fruit yogurt, chicken, etc. that will be less satiating when you puréed it and/or created a pie of it
• increasing food volume - that's not by switching from chocolate to zucchini; rather than that it's about turning a soup-like food into a foam and/or simply using water to add volume

Figure 4: Mean overall intake at a breakfast test meal (±SEM) in grams (a) and kilocalories (b) that was served after a preload with 2mm (filled) or 50 mm (open bars). * represents significance at P < 0.05 (Lett. 2016).

• modifying the lipid droplet size - emulsion with smaller droplets are more satiating than those with large(r) fat droplets (Lett. 2016)

Can xanthan reduce the glycemic response to "sweet treats" like this? Learn more in this SuppVersity Classic.

Ok, we know relatively little, but... the little we know leaves no question that satiety is not just about macros. After all, calories count and the amount of energy you will consume depends on more parameters than "your macros".

With that being said, the addition of fiber is already used extensively in the food industry. What is hardly noticed by consumers and producers alike, however, is that simply adding volume by stirring air / adding water (in)to a product will likewise add to the satiating effect of a given food; the same goes for water. In fact, up to now producers add air (e.g. ice-cream) and water (e.g. to ham) mostly to make the production cheaper. That this has satiating side effects, on the other hand, is rarely used on purpose | Comment!

References: 

• Campbell, Caroline L., Ty B. Wagoner, and E. Allen Foegeding. "Designing foods for satiety: The roles of food structure and oral processing in satiation and satiety." Food Structure (2016).
• Lett, Aaron M., Jennifer E. Norton, and Martin R. Yeomans. "Emulsion oil droplet size significantly affects satiety: A pre-ingestive approach." Appetite 96 (2016): 18-24.
• Mourao, D. M., et al. "Effects of food form on appetite and energy intake in lean and obese young adults." International journal of obesity 31.11 (2007): 1688-1695.
• Slavin, Joanne L. "Dietary fiber: classification, chemical analyses, and food sources." Journal of the American Dietetic Association 87.9 (1987): 1164-1171.