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About the value of controlling appetite • NutrInsight
In elderly subjects, the sensations of hunger/satiety are dulled by a reduction in energy needs (114) and the sense of taste. Compared to young adults, healthy elderly subjects are less hungry at the beginning of meals and become satiated sooner during a standard meal. This satiation occurs more quickly due principally to a reduction in the adaptative distension of the stomach, and an increase in the levels of CCK (115). This dulling of perceptions can lead to severe loss of bodyweight in elderly people that can be life-threatening.
Cognitive restriction
Cognitive restriction describes the tendency of individuals to restrict their food intake in order to achieve weight loss or avoid putting on weight (116;117). The restricted subject thus controls his or her food intake by exercising conscious control of the physiological factors of satiation and satiety (Herman and Polivy’s contraregulation model) (118;119;120). In industrialised countries, the restriction of food intake is a complex cultural phenomenon, which is particularly common in women and is not specific to people who are objectively overweight (121).
In practice, it is essential to characterise the subjects taking part in scientific studies of appetite control, by assessing their level of food restriction, in order to avoid the risk of reaching false conclusions. Various validated psychometric tools are commonly used: «the three-factor eating questionnaire», «the Dutch eating behaviour questionnaire» (DEBQ) and its French version (120;122;123).
Physical activity
Physical activity is a factor that can influence appetite control and, as a consequence, the regulation of food intake. According to popular belief, it is generally accepted that physical exercise stimulates appetite, which is sometimes an obstacle to (or an excuse for) doing physical exercise for people worried about their weight. However, several scientific studies have shown that physical activity is in fact associated with a transient loss of appetite, and the energy used is only partially compensated for by eating (124;125).
These outcome can depend on the duration, intensity and nature of the physical activity, and the characteristics of the subjects (whether they regularly engage in exercise, personal goals, gender, levels of food restriction). So, female subjects on a restricted diet can benefit from regular physical activity in order to control their diet better (126;127).
3.4
Eating habits and environmental factors
Hunger is, and remains, the «normal» factor that leads to eating a meal or a snack, but it is still true that eating habits and environmental factors also play a part, sometimes even a primordial role in unusual situations (cocktail parties, etc).
An experiment carried out in 114 obese subjects has shown that environmental factors, such as the usual meal time, can account for 80% of food intakes, hunger being referred to in only 20% of cases (128).
Food consumption habits
Meal times are clearly the most influential eating habit with regard to starting to eat: people eat because it is time to eat.
Thus, eating occurs during the active waking daytime phase, which is marked by the consumption of the main meals, of which there are generally three in our Western countries. This pattern, known as the «prandial» rhythm, is punctuated by inter-prandial intervals during which there are no meals. Despite this, the demand for energy remains virtually constant over the 24 hours (129). This rhythm is established spontaneously during the first three months of a baby’s life with considerable inter-individual fluctuations (influence of the parents and society) (130).
[ The powerful influence
of meal times.]
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