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NutrInsight • About the value of controlling appetite
Finally, the post-absorptive mechanisms arise mainly from the metabolism of macronutrients while still maintaining the mechanisms that regulate the pre-absorptive phase. The rise in the level of glucose in the bloodstream, as a result of the digestion of carbohydrates, the metabolism of the peptides and amino acids produced as a result of the digestion of proteins, and the assimilation of fatty acids help to maintain satiety by either direct or indirect regulatory effects (5).
The thermogenic effect of proteins appears to have an indirect role, whereas a fall in blood sugar appears to have a direct effect on satiety (cf. the glucostatic theory), in which the degree of oxidation of the energy substrates involved (glucose vs. fatty acids) appears to influence the regulation of satiety. Furthermore, when nutrients enter the bloodstream this stimulates the secretion of numerous hormones, such as leptin and insulin, which are implicated directly or indirectly in regulating satiety (17).
The concept of the satiety cascade is not static: it is subject to inter- and intra-individual changes that are influenced by time (varying from one day to another, and from one meal to another), by the diversity of the diet and by environmental factors.
In conclusion, the satiety cascade can be understood as part of a complex system of interactions involving the digestive tract, the central nervous system and also the secretion of numerous hormones and neuromediators. This system is responsible both for regulating the expression of appetite and adapting food intake to the environment (18).
1.3 Better equipped to cope with under-eating than over-eating
The neuro-hormonal control system, which regulates homeostasis in the short and long term by means of regulating appetite (via CCK, leptin, ghrelin, etc.), appears to be a powerful inducer of eating in response to the depletion of reserves and reduced energy expenditure when supplies are low (famine). In contrast, in the opposite situation (abundant supplies and/or saturation of reserves in a context of overweight or obesity for example), its ability to exert control is not sufficient (19).
In other words, this biological process has a powerful protective effect against under-eating, whereas in a context of over-eating, biological control mechanisms seem to be weak or inadequate: as a result we see what is known as “passive” over-consumption despite efforts to prevent or offset it. It is easier to put on weight than to lose it (18;20).
Increasing satiety by choosing food
Foods with the ability to generate satiety can be used to reduce the feelings of hunger, without necessarily reducing the amount eaten at the next meal. Therefore, a food that generates satiety does not necessarily mean that one will «eat less», but rather «feel better», between meals. Foods of this type may help people on a restricted-calorie diet to cope better with the periods between meals (more comfortable because less awareness of hunger); and help people with a stable bodyweight to maintain their energy balance better.
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