Influence of physiological and subjective arousal on food intake in humans

OBJECTIVES: This study explored the influence of physiologic and subjective arousal on ambient factors of the food environment, such as the eating location, the presence of other people, sound, and time of day and on food intake. It was hypothesized that the influence of environmental stimuli on food intake would be mediated by arousal. METHODS: College students were asked to wear heart rate monitors and to record their food intake in a 7-d diet diary. Subjective arousal (elation and excitement) and aspects of the eating environment were recorded for each meal occasion. RESULTS: Results showed that subjective arousal seems to be related to food intake (P < 0.01) and appears to be affected by environmental stimuli such as the eating location (P < 0.01) and the number of people present (P < 0.01), but only small effects of some environmental stimuli on heart rate were found with higher average heart rates in restaurants (P < 0.05). No effects of heart rate on food intake were detected. Regression analyses failed to show arousal as a significant mediator between environmental stimuli and food intake. CONCLUSION: It can be concluded that, for normal individuals in their everyday environment, ambient influences on food intake are not mediated by changes in arousal. However, the environment and the emotional state of the individual appear to play a role in the individual's eating behavior.     

Behavioral genetics of food intake regulation in free-living humans.

It has been established that the genes influence body size. Recently, it has become clear that food intake is also influenced by heredity. Surprisingly, the genetic effect on intake was found to occur independent of body size. Taking height and body weight into consideration, strong influences of heredity were found on the total amounts of food energy, macronutrients, and fluids ingested. Also, genetic influences were found related to the microstructure of intake, affecting the number, timing, and composition of meals. Since overall intake is determined by the size and frequency of meals, this was not surprising. However, these heritable factors were shown to influence meal size and frequency even when overall daily intake was considered in the model. Recently, we have shown that there are even heritable factors that influence the choice of the environmental conditions at the meals; the time, degree of hunger, stomach fullness, and the number and type of people at the meal. Also the degree to which these conditions affect intake appears to be heritable. These findings suggest that there are important heritable factors that influence body size, overall daily intake independent of body size, meal intake independent of overall daily intake, and the selection of and responsivity to the environmental conditions surrounding eating.     

Age and gender dependent profile of food choice

Several studies have described remarkable differences in food choice between men and women. Consistently, women are reported to have higher intakes of fruit and vegetables, higher intakes of dietary fiber and lower intakes of fat. In accordance with such more healthy food choice, women usually attach greater importance to healthy eating. In addition, the motivation of weight control is more prominent in women and they are more likely to diet or restrain their eating behavior. Recently, studies found that health beliefs and weight control motivation may explain up to 50 percent of gender differences in food choice. In addition, less healthy food choice profiles of men may be related to their poorer nutritional knowledge. However, health beliefs, eating attitudes and dieting appear to be phenomena which vary throughout the life span. In growing older, changes in the chemosensory perceptual systems play an important role in food choice. The decline of gustatory and--perhaps even more pronounced--in olfactory function may lead to a decrease of the pleasantness of food, thus limiting the reinforcing properties of food intake which eventually results in a decrease of appetite, often reported in elderly people. In addition, there are some indications that sensory-specific satiety diminishes with age. Sensory-specific satiety is the reduction in the pleasantness of food as it is consumed. This decrease of pleasantness usually motivates the choice of other foods and therefore, a varied diet. Therefore, the decrease of sensory-specific satiety may in part explain the limited variety of the diet sometimes seen in elderly people. However, lifestyle, socio-economic situation and other variables may limit the influence of such physiological changes and help to maintain an adequate food intake despite these age-related processes.     

Listening to music while eating is related to increases in people's food intake and meal duration

The relationship of listening to music while eating with food consumption in the natural environment was assessed in 78 college students. They recorded their food intake along with environmental factors such as meal duration, music, including speed and volume, location, number of people present and the time of day in a detailed diet diary for 7 consecutive days. The data show that the presence of music is associated with higher food intake. Within subject comparisons revealed higher food and fluid intake and longer meal duration while listening to music but no significant differences in music speed or volume. The likelihood of listening to music appeared to be associated with the environmental variables of the number of people present and the time of day. The presence of music appears to be one of a set of environmental factors that influences food and fluid intake in the natural world.     

Overweight children overeat after exposure to food cues

Overweight is becoming more common in children, but we know nearly nothing about the eating behavior of overweight children. Learning theory predicts that overeating follows from learned associations between the smell and taste of palatable food on the one hand and intake on the other hand. It was tested whether overweight children overeat after confrontation to these cues. They indeed failed to regulate food intake after both the exposure to the intense smell of tasty food (without eating it) and after eating a small preload of appetizing food, whereas normal-weight children decreased their intake after both cues. Overweight children are thus more vulnerable to triggers of overeating. Their overeating was not related to psychological factors like mood, body esteem, and a restrained eating style, but it was related to cue-elicited salivation flow. Apart from supporting the cue reactivity model of overeating, the data point to an interesting satiety phenomenon in normal eaters after prolonged and intense smelling palatable food without eating it.     

Genes, the environment and the control of food intake

Genes are known to have independent influences on the height and weight of individuals, their overall levels of nutrient intakes and their meal sizes and frequencies. Recent evidence suggests that genes exert multiple and subtle influences on the controls of food intake. There are significant genetic influences on the level and responsiveness of the individual to physiological factors, such as the preprandial stomach contents of nutrients and subjective hunger, and also to environmental and psychological factors such as social facilitation of eating, diurnal rhythms of intake, palatability, cognitive restraint and dietary density. The general model of intake regulation provides an integrated and comprehensive account of how these physiological and environmental factors might fit together to produce the control of intake and body weight.     

Factors that affect the food choices made by girls and young women, from minority ethnic groups, living in the UK

BACKGROUND: Lower birth weight, often found in infants from minority ethnic groups, may be partly because of the disproportionate representation of ethnic minority groups in low-income areas. To develop an intervention, to improve the nutritional intake of young women from populations at risk of low-birth-weight babies, which would be culturally sensitive and well received by the intended recipients, a community development approach was used to investigate factors that might influence food choice and the nutritional intake of girls and young women from ethnic minority groups. METHODS: Focus group discussions were conducted across the UK, to explore factors that might affect the food choices of girls and young women of African and South Asian decent. The data was analysed using deductive content analysis (Qual. Soc. Res., 1, 2000, 1). Discussions were around the broad themes of buying and preparing food, eating food and dietary changes, and ideas for an intervention to improve diet. RESULTS: The focus group discussions indicated that all the communities took time, price, health and availability into consideration when making food purchases. The groups were also quite similar in their use of 'Western' foods which tended to be of the fast food variety. These foods were used when there was not enough time to prepare a 'traditional' meal. CONCLUSION: Many issues that affect the food choice of people who move to the UK are common within different ethnic groups. The idea of a practical intervention based on improving cooking skills was popular with all the groups.     

What Everyone Else Is Eating: A Systematic Review and Meta-Analysis of the Effect of Informational Eating Norms on Eating Behavior

There is interest in the hypothesis that social norms are a determinant of healthy and unhealthy dietary practices. The objective of our work was to assess the weight of evidence that experimentally manipulated information about eating norms influences food intake and choice. This systematic review of experimental studies examined whether providing information about other peoples' eating habits influences food intake or choices. To inform the review, three electronic databases (PsycINFO, MEDLINE, and the Social Sciences Citation Index) were searched during July 2012. A narrative approach was used to synthesize studies that examined the influence of norms on food choice and meta-analyses were used to synthesize the effect that informational eating norms have on quantity of food consumed. Fifteen experimental studies were reviewed. There was evidence that both high intake norms (Z=3.84; P=0.0001; standardized mean difference 0.41, 95% confidence interval 0.20 to 0.63) and low intake norms (Z=2.78; P=0.005; standard mean difference –0.35, 95% confidence interval –0.59 to –0.10) exerted moderate influence on amounts of food eaten. There was consistent evidence that norms influenced food choices; norm information indicating that others make low-energy or high-energy food choices significantly increased the likelihood that participants made similar choices. Information about eating norms influences choice and quantity of food eaten, which could be used to promote healthy changes to dietary behavior.     

A Comparison of Food Refusal Related to Characteristics of Food in Children with Autism Spectrum Disorder and Typically Developing Children

Parents of children with autism spectrum disorder (ASD) frequently report child food refusal based on characteristics of food. Our study sought to determine whether parent report of food refusal based on the characteristics of food was greater in children with ASD than in typically developing children, associated with a greater percentage of foods refused of those offered, and associated with fruit and vegetable intake. A modified food frequency questionnaire was used to determine overall food refusal as well as fruit and vegetable intake. Parent-reported food refusal related to characteristics of food (eg, texture/consistency, temperature, brand, color, shape, taste/smell, foods mixed together, or foods touching other foods) was compared between 53 children with ASD and 58 typically developing children aged 3 to 11 years in the Children's Activity and Meal Patterns Study (2007-2008). Children with ASD were significantly more likely to refuse foods based on texture/consistency (77.4% vs 36.2%), taste/smell (49.1% vs 5.2%), mixtures (45.3% vs 25.9%), brand (15.1% vs 1.7%), and shape (11.3% vs 1.7%). No differences between groups were found for food refusal based on temperature, foods touching other foods, or color. Irrespective of ASD status, the percentage of foods refused of those offered was associated with parent reports of food refusal based on all characteristics examined, except temperature. Food refusal based on color was inversely associated with vegetable consumption in both groups. Routine screening for food refusal among children with ASD is warranted to prevent dietary inadequacies that may be associated with selective eating habits. Future research is needed to develop effective and practical feeding approaches for children with ASD.     

Eating as an automatic behavior

The continued growth of the obesity epidemic at a time when obesity is highly stigmatizing should make us question the assumption that, given the right information and motivation, people can successfully reduce their food intake over the long term. An alternative view is that eating is an automatic behavior over which the environment has more control than do individuals. Automatic behaviors are those that occur without awareness, are initiated without intention, tend to continue without control, and operate efficiently or with little effort. The concept that eating is an automatic behavior is supported by studies that demonstrate the impact of the environmental context and food presentation on eating. The amount of food eaten is strongly influenced by factors such as portion size, food visibility and salience, and the ease of obtaining food. Moreover, people are often unaware of the amount of food they have eaten or of the environmental influences on their eating. A revised view of eating as an automatic behavior, as opposed to one that humans can self-regulate, has profound implications for our response to the obesity epidemic, suggesting that the focus should be less on nutrition education and more on shaping the food environment.     

Exposure to binge food in bulimia nervosa: finger pulse amplitude as a potential measure of urge to eat and predictor of food intake

The conditioning model of binge eating states that cues such as the sight, smell and taste of binge food prepare the binger's body for the intake of large amounts of food. The bodily preparations are supposed to be felt as an almost irresistible urge to binge. In the present study, the validity of the model was tested. Clinical binge eaters (bulimia nervosa patients) and healthy control participants were exposed to their most favourite food and physiological responding was measured. As predicted, the exposure increased physiological responding and led to more intense urge to eat, but no significant differences between the bulimics and the normal controls were found. For both groups, increased urge to eat appeared to be related to finger pulse amplitude (FPA), and both the FPA and the self-reported urge to eat predicted increased caloric intake during a subsequent taste test. It is concluded that changes in FPA might reflect classically conditioned bodily responses that prepare for eating.     

Peer Reviewed: Eating as an Automatic Behavior

The continued growth of the obesity epidemic at a time when obesity is highly stigmatizing should make us question the assumption that, given the right information and motivation, people can successfully reduce their food intake over the long term. An alternative view is that eating is an automatic behavior over which the environment has more control than do individuals. Automatic behaviors are those that occur without awareness, are initiated without intention, tend to continue without control, and operate efficiently or with little effort. 

The concept that eating is an automatic behavior is supported by studies that demonstrate the impact of the environmental context and food presentation on eating. The amount of food eaten is strongly influenced by factors such as portion size, food visibility and salience, and the ease of obtaining food. Moreover, people are often unaware of the amount of food they have eaten or of the environmental influences on their eating. A revised view of eating as an automatic behavior, as opposed to one that humans can self-regulate, has profound implications for our response to the obesity epidemic, suggesting that the focus should be less on nutrition education and more on shaping the food environment.

     

Heritability of diurnal changes in food intake in free-living humans

OBJECTIVES: The time of day of meal ingestion, the number of people present at the meal, the subjective state of hunger, and the estimated before-meal contents in the stomach have been established as influences on the amount eaten in a meal, and this influence has been shown to be heritable. Because these factors intercorrelate, the possibility that the calculated heritabilities for some of these variables could result indirectly from their convariation with one of the other heritable variables was assessed. METHODS: The independence of the heritability of the influence of these four factors was investigated with 110 identical and 102 fraternal same-sex and 53 fraternal mixed-sex adult twin pairs who were paid to maintain 7-d food intake diaries. From the diary reports, the meal sizes were calculated and subjected to multiple regression analysis using the estimated before-meal stomach contents, the reported number of other people present, the subjective hunger ratings, and the time of day of the meal as predictors. Linear structural modeling was applied to the beta coefficients from the multiple regression to investigate whether the heritability of the influences of these four variables was independent. RESULTS: Significant genetic effects were found for the beta coefficients for all four variables, indicating that the heritability of their relationship with intake is to some extent heritable. CONCLUSIONS: These results suggest that the influences of multiple factors on intake are influenced by the genes and become part of the total package of genetically determined physiologic, sociocultural, and psychological processes that regulate energy balance.     

The physiological-psychological dichotomy in the study of food intake

Human food intake is driven by necessity. We eat to live, but as Brillat-Savarin and others have noted throughout history, in affluent societies eating is a pleasure and becomes more than a means to an end. Eating signifies lifestyle choice and it has considerable meaning in our society beyond the acquisition of essential energy and nutrients. Thus, it is that the study of human food intake, particularly food choice, in contrast to food intake in other animals, tends to be skewed towards measures of behavioural, social and environmental influences rather than on precise physiological processes reflecting metabolism and nutrient partitioning. The dichotomy between physiological and psychological measures is a false one, since all behaviours are necessarily expressed through physiological systems. However, in the field of human food intake research the dichotomy refers to the divergent strands of interest in either psychological or physiological processes underlying intake and appetite. The present review considers both psychological and physiological measures in promoting our understanding of the human appetite system. The overall conclusion is that the burgeoning interest in identifying appetite suppressant drugs to combat obesity and in genotyping alongside behavioural phenotyping will close the gap between psychological and physiological perspectives on human food intake.     

Environmental Strategies to Promote Food Intake in Older Adults: A Narrative Review

Aging is often accompanied by lower intakes of food energy and consequent negative effects on health. To some extent this is due to declines in physiological ability, including the sensory responsiveness to regulate food intake. Fortunately, environmental factors may still influence food intake in older adults. Factors such as social facilitation, modeling, and nutrition knowledge and skills have been shown to stimulate their food intake. While environmental factors such as the eating location, portion size, food presentation, and labeling are known to influence eating behavior, their effectiveness in stimulating food intake in older persons is not well delineated. It is suggested that improving the environmental stimuli that promote food intake is a viable strategy to overcome age-related declines in nutrient intakes. This strategy is so promising that further research is warranted.     

Children eat their school lunch too quickly: an exploratory study of the effect on food intake

ABSTRACT: BACKGROUND: Speed of eating, an important aspect of eating behaviour, has recently been related to loss of control of food intake and obesity. Very little time is allocated for lunch at school and thus children may consume food more quickly and food intake may therefore be affected. Study 1 measured the time spent eating lunch in a large group of students eating together for school meals. Study 2 measured the speed of eating and the amount of food eaten in individual school children during normal school lunches and then examined the effect of experimentally increasing or decreasing the speed of eating on total food intake. METHODS: The time spent eating lunch was measured with a stop watch in 100 children in secondary school. A more detailed study of eating behaviour was then undertaken in 30 secondary school children (18 girls). The amount of food eaten at lunch was recorded by a hidden scale when the children ate amongst their peers and by a scale connected to a computer when they ate individually. When eating individually, feedback on how quickly to eat was visible on the computer screen. The speed of eating could therefore be increased or decreased experimentally using this visual feedback and the total amount of food eaten measured. RESULTS: In general, the children spent very little time eating their lunch. The 100 children in Study 1 spent on average (SD) just 7 (0.8) minutes eating lunch. The girls in Study 2 consumed their lunch in 5.6 (1.2) minutes and the boys ate theirs in only 6.8 (1.3) minutes. Eating with peers markedly distorted the amount of food eaten for lunch; only two girls and one boy maintained their food intake at the level observed when the children ate individually without external influences (258 (38) g in girls and 289 (73) g in boys). Nine girls ate on average 33% less food and seven girls ate 23 % more food whilst the remaining boys ate 26% more food. The average speed of eating during school lunches amongst groups increased to 183 (53) % in the girls and to 166 (47) % in the boys compared to the speed of eating in the unrestricted condition. These apparent changes in food intake during school lunches could be replicated by experimentally increasing the speed of eating when the children were eating individually. CONCLUSIONS: If insufficient time is allocated for consuming school lunches, compensatory increased speed of eating puts children at risk of losing control over food intake and in many cases over-eating. Public health initiatives to increase the time available for school meals might prove a relatively easy way to reduced excess food intake at school and enable children to eat more healthily.     

Intrapair comparisons of diet and food preference in adult twins

OBJECTIVES: An investigation was conducted on the influence of genetic and lifestyle factors related to the determination of eating behavior of human beings. The objective was to obtain information about lifestyle factors that may help health professionals intervene in terms of the prevention of diet-related diseases. METHODS: The subjects were 180 pairs of adult twins aged over thirty, comprising of 134 monozygotic (MZ) and 46 dizygotic (DZ) pairs. Every subject was given an interview concerning dietary habits, food preference, food intake, as a part of medical examination. The intake of food containing salt and fat, the intake of food meals, the frequency of daily meals, and the frequency of eating 18 sorts of food were assessed on an individual basis, with a questionnaire on nutrition. The expected and observed values of intrapair concordance rates were calculated, and compared within each zygosity, using the chi-square test. RESULTS: Significant differences between the expected and observed for intrapair concordance rates were shown with monozygotic twins, regarding every category of question. Comparing MZ pairs who had lived apart before their twenties with the other MZ pairs, the latter had a tendency to show significant differences between the expected and observed values of intrapair concordance rate, regarding every category of question. In each case, the observed values were higher than the expected values. CONCLUSIONS: The study implied that both genetic and lifestyle factors influence the determinants of eating behavior of human beings. This finding shows the importance of understanding individual characteristics of food preference and eating behavior for intervention regarding lifestyle factors for prevention of diet-related diseases.     

Qualitative study of influences on food store choice

Previous research indicates food store choice influences dietary intake and may contribute to health disparities. However, there is limited knowledge about the reasons which prompt the choice of a primary food store, particularly among populations vulnerable to obesity and chronic diseases (e.g., individuals living in rural locations and African-Americans). Purposive sampling was used to select rural and urban communities (three African-American and two Caucasian focus groups; n=48) in Arkansas from June to November 2010, allowing examination of potential racial or rurality differences. Primary household food shoppers (n=48) (96% female, 63% African-American, mean age=48.1±13.9years old, mean BMI=30.5±7.8) discussed reasons for choosing their primary store. Qualitative analysis techniques-content analysis and constant comparison-were used to identify themes. Four themes emerged: proximity to home or work, financial considerations and strategies, availability/quality of fruits, vegetables, and meat, and store characteristics (e.g., safety, cleanliness/smell, customer service, non-food merchandise availability, and brand availability). While there were persistent rurality differences, the relevant factors were similar between African-American and Caucasian participants. These findings have important implications for future policies and programs promoting environmental changes related to dietary intake and obesity, particularly in rural areas that appear to have significant challenges in food store choice.