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NutrInsight • Satiety: from appetite sciences to food application
ingestion, such as gastric distension, and hormonal responses, such as the drop in stomach ghrelin that takes place during a meal, progressively build up and finally determine meal termination. Numerous other factors act on satiation, such as cognitive influences (expectations, beliefs, attention) and possible metabolic responses such as the release of insulin during the “cephalic phase of digestion”.
Satiety is concerned with the inhibition of the motivation to eat that follows food consumption. The expression of satiety represents an interaction between the nature of the food eaten, the physiological system and the psychological state. The time course of satiety is critical and the post-prandial period can be divided into distinct phases. A succession of sensory, cognitive, post-ingestive, and post-absorptive influences inhibits further eating following the intake of a food or meal.
The sensory characteristics (smell, taste, shape, colour) of the ingested foods continue to inhibit intake of other foods that share similar characteristics in the hours that follow ingestion. Expectations about the satiety value or the energy load of the food also affect the early satiety effects. Later on, nutritionally distinct foods provoke the release of different patterns of satiety and orexigenic peptides from the gastro-intestinal tract with particular time courses. The satiating efficiency of the ingested foods depends on their weight, volume, energy and nutrient content. For a given energy load, higher energy density weakens satiation and allows the intake of large amounts of energy. A hierarchy of satiating power has been demonstrated: proteins are considered more satiating than carbohydrate (CHO), which in turn are more satiating than fats. However, this rank order should not be taken too literally; mixtures of nutrients can modify the intensity and duration of satiety in a variety of ways. The presence of fibre contributes to increasing satiety and certain types of fibre might exert more potent effects than others.
Meal quality Expectations
Reward/Pleasure Recognition Associations
Sensation +
prior beliefs and associations
SENSORY
Meal quantity Stretch
Osmotic load CCK · GLP-1 PYY · Ghrelin
Stomach + intestines
COGNITIVE POST-INGESTIVE
Nutrient status Insulin
Oxidation Glucose Amino acids
Liver + metabolites
POST-ABSORPTIVE
LATE
Energy balance
Insulin
Leptin Adiponectin (?)
Fat-free mass Fat mass RMR
FOOD
Satiation
EARLY
Satiety
Figure 1: updated version of the original Satiety Cascade, revised by Mela and Blundell.
CCK: cholescystokinin; GLP-1: Glucagon-like peptide-1; PYY: peptide YY.
Source: Blundell et al., 2010
These signals from the periphery are integrated by the brain whose activity ultimately controls the alternating pattern of intake and satiety. A later section is devoted to the recent development of neuroimaging, illustrating the brain mechanisms underlying various aspects of satiety (See chapter 5 by Pr. Hans Rudolph Berthoud). The modern approach to satiety includes the consideration of both homeostatic and hedonic processes. The brain responds both to signals indicating the body energy balance status and to hedonic reward.
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