Social aspects of eating Flashcards
Settling-point theory
A lot of work is being done on the biology of fat cells. Researchers in Sweden recently discovered that people tend to drop out of weight loss programmes – not when they had attained their target weight – but when their fat cells had reached normal size. For two people of the same height, this could occur at greatly different weights. One person may have more fat cells than the other. Some overweight children and morbidly obese adults are known to have more fat cells than usual. This is called hyperplastic obesity. Fat cells are usually formed at two critical periods of a person’s life – in early childhood and at puberty. We now know that new fat cells can be formed at any time of life if weight is gained rapidly or if fat cells grow to over 50% of their normal size. Similarly, if people try to reduce their weight to the point where their fat cells shrink below normal size, the organism starts to behave as if starving (even if they eat fairly well). People with fat cells below normal size display all the usual symptoms of people with eating disorders (craving food, being obsessional and ritualistic). So there is obviously some kind of biological pressure to keep fat cells at approximately their normal size, even if technically this means that a person may be culturally “overweight. This provides evidence for the Set Point Theory which is described below.
Other positive incentives: Conditioned cues elicit feeding in sated rats: a role for learning in meal initiation (Weingarten 1983).
Social &environmental factors in hunger “organisms eat not only as a result of energy demands but also in response to other factors not directly associated with energy depletion” ABSTRACT: Pavlovian conditioning was used to teach rats an association between an arbitrary external cue and food. Presentation of the conditioned cue elicited feeding by sated animals. The meal constituted approximately 20 percent of daily intake, and it was compensated for by a reduction of subsequent intake. CS+ buzzer + light paired with food CS- intermittent pure tone Rats ate even when satiated Feeding elicited by CS+ made up a significant proportion of daily intake. Social & environmental factors in hunger: Seeing food / hunger as conditioning •Sensory specific satiety & food variety •Time of day •Portion size •TV •Other social factors.
Sensory specific satiety: Rolls et al
Sensory-specific satiety is a sensory hedonic phenomenon that refers to the declining satisfaction generated by the consumption of a certain type of food, and the consequent renewal in appetite resulting from the exposure to a new flavor or food. Its concept illustrates the role of physical stimuli in generating appetite and, more specifically, explains the significance of taste in relation to hunger. Besides conditioned satiety and alimentary alliesthesia, it is one of the three major phenomena of satiation. “the decline in pleasantness of the flavour of a specific food that has just been eaten in contrast to other non-consumed foods” • Rate all foods • Eat one food for lunch • Rate all again. Sensory specific satiety: • Food specific • Rapid onset • Long-lasting. • Participants in different groups eat one type of food (different in each groups) for lunch • They are then given a surprise 2nd course, which could either be of the same or different type of what they have just eaten à Who is likely to eat more? We get full faster if meals are limited to one food type •Therefore variety of food increases meal size •E.g. rats given bread & chocolate after usual meal started ingesting 84% more calories than usual •After 120 days on this diet, their body weight had increased by 49% •Similar effects can be seen in humans.
Time of day (circadian rhythms); How Sugar Tunes Your Clock (Hart et al, 2013)
A circadian rhythm is a roughly 24 hour cycle in the physiological processes of humans and non-humans animals. Circadian rhythms are important in determining the feeding patterns. P Synchronizing all the clocks in the body is essential for the body to function at its best Eating at certain times of the day, which vary depending on sleep habits, may lead to optimal body functionality via clock synchronization. •In the morning, the ‘central’ clock responds to the light •If fasting, the ‘peripheral’ clocks respond to lack of food, which creates a di-synchrony between the clocks. •Mice with this di-synchrony appear ill, and are not as active or energetic as those with synchronous cycles. Abstract: While cellular circadian clocks are set by the light/dark cycle, these clocks can be reset by what we eat. Two papers in this issue of Cell Metabolism revealthat O-GlcNAcylation of clock proteins, which is dependent on nutrients, adjusts our circadian clock (Kaasik et al, 2013; Li et al, 2013). All of our cells have a ~24h clock(termed, circadian clock) that is primarily set by light, but also is modified by environmental cues, especially nutrients, such as glucose(Damiola et al. 2000). However, the molecular mechanism of nutrient regulation of our cellular clocks is largely unknown. Current models suggest that our circadian clocks are comprised of transcriptional auto-regulatory feedback loops controlled by specific transcription factors (Mohawk et al., 2012). Prior work has shown that the rate of cycling of the clock auto-feedback loops are modulated by several regulatory mechanisms, including post-translational modifications (PTMs) of clock transcription factorsby acetylation, ADP-ribosylation, phosphorylation and ubiquitination(Asher and Schibler, 2011).For example, in one such auto-feedback loop,heterodimers of the transcription factors CLOCK and BMAL1 bind E-box elements in DNA to activate the expression of Period (Per)andChryptochrome (Cry) proteins, which accumulate in the cytosol until they are phosphorylated and enter the nucleus where they inhibit the activity of CLOCK/BMAL1 (Figure 1). Degradation of the inhibitory Per and Cry proteins restarts a new cycle of the circadian clock (Ukai and Ueda, 2010). These transcription factor feedback loops are highly conserved in biology.
Social factors in eating behaviour Increasing the portion size of a packaged snack increases energy intake in men and women (Rolls et al 2004).
Abstract; The objective of this study was to determine how the portion size of a packaged snack affects energy intake of the snack and of the subsequent meal. On five separate days, 60 subjects (34 women and 26 men) ate an afternoon snack and dinner in individual cubicles. For each snack, subjects were served one of five packages of potato chips (28, 42, 85, 128, or 170 g), which they consumed ad libitum directly from the unlabelled, opaque package. Subjects returned to the lab three hours later for a standard dinner, which was also consumed ad libitum. Results showed that snack intake increased significantly as the package size increased for both males and females
Social factors in eating behaviour Effect of ambience on food intake and food choice (Stroebele & Castro 2004)
Abstract; Eating takes place in a context of environmental stimuli known as ambience. Various external factors such as social and physical surroundings, including the presence of other people and sound, temperature, smell, colour, time, and distraction affect food intake and food choice. Food variables such as the temperature, smell, and colour of the food also influence food intake and choice differently. However, the influence of ambience on nutritional health is not fully understood. This review summarizes the research on ambient influences on food intake and food choice. The literature suggests that there are major influences of ambience on eating behaviour and that the magnitude of the effect of ambience may be underestimated. Changes in intake can be detected with different levels of the number of people present, food accessibility, eating locations, food colour, ambient temperatures and lighting, and temperature of foods, smell of food, time of consumption, and ambient sounds. It is suggested that the manipulation of these ambient factors as a whole or individually may be used therapeutically to alter food intake and that more attention needs to be paid to ambience in nutrition-related research.
Social factors in eating behaviour What is the role of portion control in weight management? Rolls (2014)
Abstract; Systematic studies have shown that providing individuals with larger portions of foods and beverages leads to substantial increases in energy intake. The effect is sustained over weeks, supporting the possibility that large portions have a role in the development of obesity. The challenge is to find strategies to effectively manage the effects of portion size. One approach involves teaching people to select appropriate portions and to use tools that facilitate portion control. Although tools such as portion-control plates have been shown in several randomized trials to improve weight loss, limited data are available on whether education and tools lead to long-term changes in eating behavior and body weight. Another approach is to use preportioned foods (PPFs) to add structure to meals and minimize decisions about the amount of food to eat. A number of randomized controlled trials have demonstrated the efficacy of both liquid meal replacements and solid PPFs for weight loss and weight loss maintenance, but it is not known if they lead to better understanding of appropriate portions. Although portion control is important for weight management, urging people simply to ‘eat less’ of all foods may not be the best approach as high-energy-dense foods disproportionately increase energy intake compared with those lower in energy density. A more effective strategy may be to encourage people to increase the proportion of foods low in energy density in their diets while limiting portions of high-energy-dense foods. If people lower the energy density of their diet, they can eat satisfying portions while managing their body weight.
Social factors in eating behaviour Spontaneous meal patterns of humans: influence of the presence of other people. de Castro & de Castro (1989)
Abstract: Social influences on eating were investigated by paying 63 adult humans to maintain 7-d diaries of everything they ingested, time, subjective hunger, and number of people present. Meals eaten with others contained more carbohydrate, fat, protein, and total calories; had smaller deprivation ratios; and had larger satiety ratios than meals eaten alone. The number of people present was positively correlated with meal size even when meals eaten alone were excluded. Adding the number of people present as a factor in a multiple-regression prediction of meal size more than doubled the variance accounted for, without altering the influence of other predictors, suggesting that social factors are associated independently with an increase in meal size. Meal size was positively correlated with the postmeal interval for meals eaten alone but not for meals eaten with other people. This suggests that social factors increase amounts eaten and disrupt postprandial regulation. •Transmission of food preference •Eating in the presence of others eating •Increased meal size in social situations diary study showed positive relationship between amount of food eaten & number of people present; meals eaten with others 44% bigger than those eaten alone.
Social factors in eating behaviour Variety enhances food intake in humans: Role of sensory- specific satiety (Brondel, 2009)
Twenty-one subjects were studied to evaluate the effect of renewal of sensory stimulations of previously eaten foods on sensory-specific satiety and intake. The subjects ate French fries then brownie cakes ad libitum (at one’s pleasure) in three situations: “monotonous”—fries then brownies were consumed alone; “simultaneous”—condiments (ketchup and mayonnaise for the fries, vanilla cream and whipped cream for the brownies) were added during intakes; “successive”—after intake of fries alone, ketchup then mayonnaise were available with fries and, after intake of brownies alone, vanilla cream then whipped cream were offered with brownies. The quantities eaten in the “simultaneous” and “successive” situations were higher (pb0.001) than those in the “monotonous” one. In the “successive” situation, hedonic ratings for fries diminished during intake but increased after the introduction of ketchup, leading to additional intake of fries. Similarly, hedonic ratings for brownies diminished during intake and increased after the introduction of vanilla cream leading to additional brownie intake (mayonnaise and whipped cream had no significant effect). Food variety, obtained by adding condiments can increase food intake in the short term. The mechanism by which food consumption is increased after the addition of condiments is introduced is at least partly related to the attenuation of sensory-satiety for a given food.
NEUROPHYSIOLOGY OF HUNGER AND SATIETY (Smith and Ferguson, 2008)
Hunger is defined as a strong desire or need for food while satiety is the condition of being full or gratified. The maintenance of energy homeostasis requires a balance between energy intake and energy expenditure. The regulation of food intake is a complex behaviour. It requires discrete nuclei within the central nervous system (CNS) to detect signals from the periphery regarding metabolic status, process and integrate this information in a coordinated manner and to provide appropriate responses to ensure that the individual does not enter a state of positive or negative energy balance. Smith and Ferguson (2008) examined the CNS circuitries involved in the control of energy homeostasis as well as signals from the periphery, both hormonal and neural that convey pertinent information regarding short-term and long-term energy status of the individual.
