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NutrInsight • About the value of controlling appetite
Depending on the individual’s country and lifestyle, there are considerable differences in meal times, the most common being the times when the midday and evening meals are taken (earlier in the USA than in France, for instance) or where meals are eaten (more often at home and earlier in the provinces than in cities). The traditional pattern of three or four meals is still fairly stable in Europe in terms of meal times (131), but some erosion is beginning in response to socio-economic factors (the development of round-the clock availability of meals of the fast-food type) (132), which makes the regulation of food consumption more precarious.
Finally, the influence of «It’s time to eat» leads people to eat at a fixed time even if they are not actually hungry: subjects disconnected from the notion of time, under experimental conditions, delayed their next food intake after eating a loading meal with a high energy content, for longer than those who were aware of the passage of time (133). In this sense, the established pattern of human meal times, if it is disconnected from any sensation of hunger, constitutes a risk for becoming overweight.
If meal times are the most influential factor, the food culture of the individual’s country and family also have a considerable impact on eating behaviour: numerous studies by Bellisle and de Castro have demonstrated a positive correlation between overweight in parents and in their children (134;135;136;137).
Environmental factors
As well as these eating habits, many environmental factors also influence food intake. These include portion size, which seems to be of primordial importance. Thus, many studies have shown that feeding teenagers and adults with bigger portions of food leads to a significant increase in their energy intake (82;138;139). These effects, which have also been demonstrated for snacks and a range of simple meals, last for a period of more than two days. Despite eating more, individuals given larger portions do not generally report or display greater fullness, suggesting that hunger and satiety signals are ignored or go unnoticed (140).
Apart from portion size, many other secondary factors linked to the environment are also involved, notably:
- the size of the container (packaging or plate/bowl/glass): The bigger the packaging or plate (or bowl or glass), the greater the amount consumed (141;142).
- sharing a meal with other people: there is a positive correlation between the number of people sharing a meal and the quantity and quality of the food eaten (the calorie content per person is increased on average by 76% when a meal is shared with more than 7 other people, with an increase in all nutrients) (137;143).
- the ambience in terms of light, noise, smells, temperature, etc. : a soft, filtered light tends to increase the duration of the meal, but to reduce the volume ingested (144;145), conversely, bright light tends to facilitate over-consumption within a short time (fast food restaurants for example) (146). The background sound level also plays a role (147): quiet music prolongs the duration of the meal and increases the consumption of drinks (148), whereas a very noisy environment with an upbeat tempo, produces stress that in turn induces an increase in consumption, in chewing movements and the speed at which food is ingested (149;150). The influence of the surrounding smell is more complex: a smell that is experienced as enjoyable
helps to trigger starting a meal, but nevertheless it does not increase the quantity of food ingested (151). With regard to temperature, the use of air- conditioning tends to increase the amount of food eaten in restaurants, canteens, etc. (152). Finally, in general, studies tend to report greater food intake when a meal is eaten in a restaurant rather than at home (137;153;154).
[ Bigger portions lead to greater consumption. ]
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