Satiety: Chews your food wisely

Over 100 years ago a health enthusiast named Horace Fletcher warned us that “nature would castigate those that don’t masticate” One hundred ears on and we live in an ‘obesogenic’ food environment characterized by highly palatable, high energy dense foods that are often served in large portions.  These features combine to promote energy intake, and when the foods are softly textured, they can increase the rate of eating (g/min) and promote energy intakes even further.  The current global rates of obesity would be enough to make Fletcher grind his teeth in disappointment!

We are told that hyper-palatable, energy dense foods rich in sugar and fat and are ‘engineered’ to be less satiating and to encourage consumption.  These commonly come in packaged processed foods but also in the home food environment where energy dense Dauphinoise potatoes, tagliatelle carbonara and cheesecake can also promote passive overconsumption. Very high levels of fat and sugar are absolute characteristics of dessert dishes such as franigpan or baklava and are more often home made than purchased as a prepared dish.  However we may well ask, is it possible to also apply the same rationale to reversing this trend and use the sensory properties of foods to promote eating behaviour’s that drive satisfaction while supporting energy intake reductions? 

This is the approach being applied by a group of researchers led by Professor Ciaran Forde at the Clinical Nutrition research Centre of the National University of Singapore in one of their recent scientific publications[1].

The authors begin with an elaboration of the research that they and others have done, which show definitively, that the rate at which we eat a food (eating rate: ER) greatly influences overall meal intake.  The basic unit in this regard is grams of food per minute and is strongly influenced by bite size and the total number of bites taken within a meal.  That determines what goes into the mouth. Thereafter, the key measures are chews per bite and time in mouth with the longer the chewing the more satiating the food per kcal consumed (remember what Fletcher said about ‘castigate’ and ‘masticate’).  In effect this is about bites, chews and swallows.  All can be quantified using simple behavioural coding of video recordings of people as they eat.  All available evidence shows that the larger the portion size, the greater energy density, and the faster one eats, the more energy is consumed within a meal. The key question posed by the team in Singapore is whether we could use food texture to better regulate food intake within a meal and could this offer some protection against larger portions and higher energy density?  They opted to conduct their experiments with a traditional rice-based breakfast widely consumed in Singapore among a group of healthy regular breakfast consumers.  The key part of the study was to modify the texture of the breakfast to effect a change in eating rate, and this was achieved by greater or lesser milling of white and brown rice grains.  The energy density served was low (0.5kcal/g) or high (1.0kcal/g) and was changed by varying the amount of both sunflower oil and the starch product, maltodextrin.  In the study, the portion sizes offered were either 700 grams or 1050 grams. Thus the effect of thickness was examined for a given portion size when energy density varied and in the second study, the effect of thickness was studied when energy density was held constant but with portion size varied. The key points of the results are as follows:

Þ   Constant portion size: Increasing the thickness of the breakfast led to a higher bite size (about 30% higher), higher oral exposure per bite (about twice as high) and more chews per bite (about three times higher). This was not influenced by the energy density of the diet. The overall eating rate was halved by the thicker porridge leading to a decline in caloric intake at breakfast of about 75 calories

Þ   Constant energy density: Higher portion sizes led to an increase in breakfast intake compared to smaller portion size (487 v. 425 g). Thicker porridges led to lower intakes than thinner porridges (425 v. 488g). The thicker porridge almost halved the eating rate.

The bottom line is that by manipulating texture, significant beneficial effects in caloric intake from the test breakfast were seen.  Thus the options for the reformulation to consider extend beyond portion size and energy density to also use food texture in a way that effectively changes eating behaviour.  In each case there were no differences in post-meal hunger or fullness and the changes did not reduce palatability, if anything in the thicker breakfast liking tended to go up.  These results are encouraging at a time when food processing is under attack and the results suggest that processing techniques like thickening, hardening, extruding and adding ‘crunch’ can be used to change our eating behaviours and effect a change in energy intake without a loss in eating pleasure or satisfaction.

Food technology can help alter the characteristics of foods such as texture and energy density to extend eating time and thus to reduce energy intake.  Here is where the rubber hits the road.  How do everyday food choices and eating behaviours, which are often habitual and routine link up with our internal biologic control of food intake? With the huge failure rates of dieting with a 2-year relapse rate of about 50% and a 5-year relapse rate of about 95% we can ask – is it possible to restrict intake long term to prevent weight re-gain? The study described above could help to mitigate the need to feel restricted or deprived, by re-engineering the food environment to extend the eating time for meals and support energy reductions. 

We are largely unaware of the precise energy content of the foods we eat, and the largest variations in energy intake tends to occur within meals in calories consumed to the onset of fullness (satiation).  The present study is one of a new breed of controlled feeding trials that highlight how a food’s sensory properties can be used to promote fullness and show that the act of consuming a satisfying meal is itself a strong satiation cue. Here we see the application of sensory properties like meal texture to not only promote palatability and liking, but also to act as functional cues to promote satiation and satiety. All this is now possible in the modern processed food world, far removed from the original ideas proposed by Horace Fletcher. Today, modern food processing techniques contribute food safety, and reformulation and food processing techniques can be applied to change energy density, and enhance the eating experience through food texture. 

My thanks to Prof Ciaran Forde for fact-checking and editorial input.

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[1] Keri McCrickerd et al (2017) Texture based differences in eating rate reduce the impact of increased energy density and large portions on meal size in adults. Journal of Nutrition, March 27^th.