Motivation and emotion/Book/2011/Self-regulation of overeating
What causes overeating and how to get it under control?
What is overeating?
At its simplest form, overeating is characterised by excessive consumption of food beyond what is needed to achieve satiety. While this is a reasonably common occurrence, compulsive overeating is linked to more serious conditions such as bulimia or binge eating disorder and obesity (Stoebe, 2008, p. 7).
Although there are physiological cues for hunger and satiety, most people cognitively control what, when and how much food they eat. This self-regulation often fails and results in overeating, which increases the risks of weight gain and the associated adverse health affects of obesity (Baumeister, Heatherton & Tice, 1994, p. 242).
This chapter aims to determine the physiological hunger cues, patterns of self-regulation and the possible reasons why self-regulation of eating fails. In doing so this chapter also points out practical applications of the theory and research to help the reader avoid lapses in self-regulation that result in overeating.
|“||One should eat to live, not live to eat.
- Benjamin Franklin
The physiological motivation to eat
The consumption of food is a basic physiological need, meaning that eating is essential to maintain life as well as support growth and well-being. In being a physiological need, the motivation to eat is to some extent biological, controlled by neural and hormonal mechanisms. These mechanisms include:
The glucostatic theory
This concept, proposed by Jean Mayer in the 1950’s, states that nerves in the lateral hypothalamus of the brain detect a rise in blood glucose levels (BGLs). When stimulated these nerves cause a sense of satiety and eating behaviour is stopped. Conversely the decline of BGLs in-between meals causes increasing hunger by stimulating the ventromedial hypothalamus (Chaput & Tremblay, 2009).
This theory of short-term appetite control is supported by recent research into the effect of high and low glycaemic index (GI) foods on hunger and satiety. Low GI foods, which slowly increase BGLs, are linked to increased satiety and a reduction in food intake throughout the day. What is more, high GI foods which cause a rapid rise and fall of BGLs, are associated with only short term satiety, resulting in an earlier sense of hunger and increased overall food intake (Warren, Henry & Simonite, 2003).
Stomach distention is another short-term regulator of appetite. During a meal the stomach expands to accommodate the intake of food. The expansion is detected by gastric stretch receptors, which send a neural signal to various parts of the brain, including the amygdala and insula. This process results in a perception of fullness and causes eating behaviour to stop (Wang et al., 2008).
The stomach empties at a constant rate of approximately 880 kilojoules (kJ; aprox 210 calories) per hour. Thus, high kJ meals take longer to exit the stomach than low kJ meals, keeping the stomach distended for longer and increasing the time before appetite returns (Hunt & Stubbs, 1975)
Other short term appetite controls
Sight, smell, taste and thought cues
All of these sensations stimulate the cephalic reflexes. The cephalic reflexes are autonomic and endocrine responses, including increased saliva and gastric juice secretion, which prepare the body for digestion. These reflexes are the cause of the drooling over the smell of something cooking, or the tummy grumbles at the thought of a favourite food.
While these are primarily physiological responses to sensory inputs we can be trained to associate things, that are originally unrelated to eating, with food. Ivan Pavlov proved this by conditioning dogs to associate the ringing of a bell with food, thereby causing the stimulation of the dog’s cephalic reflexes. Similarly, in everyday life people associate midday with lunch and start to salivate and have tummy grumbles (Giduck, Threatte & Kare, 1987).
Based on studies in animals, it may be that people have a greater intake of food in cold environments than warm ones. In cold climates the body must use energy to maintain core body temperature. This phenomenon is possibly caused by increased energy expenditure required to maintain core temperature in colder conditions. The evidence surrounding this physiological control of appetite is limited and this is definitely an area for further research (Brobeck, 1960).
Long-term energy intake is suspected to be regulated by hormones secreted from adipose tissue, namely ghrelin and leptin. As adipose tissue is our store of energy for times of fasting, the body aims to keep fat mass a optimal homeostatic levels. A drop in fat mass stimulates an individual to consume more to replace those fat stores. This is mediated by the hormone ghrelin, which is secreted by adipose tissue when fat stores decrease. Ghrelin causes the stimulation of the, which promotes the weight gaining behavior of increasing food intake. However, when fat stores exceed the homeostatic level adipose tissue secretes the hormone leptin. Leptin stimulates the ventral medial hypothalamus, which increases satiety, decreases eating behaviour and prevents further weight gain (Cummings & Shannon, 2003).
Failure to self regulate food intake
|“||Don't dig your grave with your knife and fork
- English Proverb
Self-regulation of eating refers to deliberate attempts to control food intake, often in defiance of normal regulatory influences, and usually with the goal of achieving or maintaining weight loss (Baumeister & Heatherton, 1996). Self-regulation is influenced by several psychological, social, cultural and environmental factors, many of which contribute to a failure of self-regulation resulting in overeating. According to Baumeister, Heatherton and Tice (1994) the factors that cause self-regulation failure are distinguished into two patterns of behaviour: under regulation and misregulation
Under regulation refers to failure to exercise self-control and is made up of four patterns of behaviour: Conflicting standards, a reduction in monitoring, inadequate strength or willpower and psychological inertia.
In recent decades the Western world has experienced a movement towards the thin ideal, the social desirability of a slender body shape, particularly in women. Perpetuated by the modern media, this aesthetic standard of beauty has a significant impact on women’s eating patterns. Dieting is the conscious restriction of food intake to reduce or maintain weight.
Restraint theory was developed in the 1970’s and focuses on the association between cognitive control of eating and food intake, in order to determine the causes and consequences of restrained eating (Ogden 1994). While restrained eating or dieting aims to reduce food intake, and in some cases this does work, often restrained eating results in increased food intake. The restraint theory suggests that restraint not only precedes overeating but contributes to it.
People consume more when they restrain eating and allow themselves to become exceptionally hungry. While this seems obvious (people who are hungry eat more than those who are not hungry), people feeling ‘starving hungry’ then overeat, consuming more kJ than necessary to satisfy hunger (Polivy 1996). Several studies support this theory and demonstrate that restrained eatin, often leads to a loss of control, poor food choices and a tendency to overeat or binge (Vitousek 2004; Polivy and Herman 2006; Polivy 2008). For instance, in a study by Polivy, Coleman & Herman (2005) it was shown that individuals deprived of chocolate for a week experienced greater craving and consumed more chocolate at the end of deprivations compared to those who were not chocolate deprived.
What is more, food restriction causes neurological adaptations relating to the reward of food. Food restriction can prevent negative alliesthesia, the process in which a sweet food becomes unpleasant to taste. This means that sweet foods that become sickening to non-restrained individuals do not become unpleasant to food-restricted individuals, causing them to consume more of these high-energy foods (Cabanac & Lafrance 1996; Cabanac et al 1971).
Goal conflict theory
The goal conflict theory of eating was developed by Wolfgang Stroebe and colleagues to provide a realistic model of the cognitive processes by which restrained and unrestrained individuals control their food intake. This theory suggests that restrained eaters experience a conflict between two goals, the goal to loose or maintain weight and the goal to enjoy palatable food. While these are both highly desirably end states for restrained eaters, the desire to loose weight is often the stronger of the two. Despite this, chronic dieters are sensitive to an environment rich in stimuli signaling or symbolising palatable food. Temptation activates automatic attempts to achieve the goal of weight loss through inhibiting thoughts of the pleasure of eating. However continued exposure to palatable foods is likely to override the long-term goal of weight loss in chronic dieters and result in over eating (Stroebe, 2008, p. 163).
This theory is supported by research including a study by Papies, Stroebe and Aarts (2008), which examined the effect of food cues on restrained eaters' attention for food. It was found that restrained eaters paid more attention to palatable food when they had been pre-exposed to food cues such as appetising food words, while unrestrained eaters did not increase attention to palatable food.
Advertising and food availability
The findings of Papies et al. (2008) along with similar research findings, suggest that food intake can be primed by external messages such as advertising. Priming refers to increasing the sensitivity of an individual to a particular stimuli as a result of a prior experience. Research by Harris, Bargh and Brownell (2010) revealed that both children and adults consumed more snack foods after being exposed to an advertisement, compared to other conditions. This increase in food intake was not related to hunger reports and foods that were consumed were not necessarily the foods advertised.
This is a particularly important issue in current western society, in which food advertising is so prevalent. In an Australian study showed that between 7am and 9pm 31% of television advertisements were for food and beverages, approximately 80% of which were for unhealthy foods (Worsley, 2008). Furthermore, TV advertising exposure is linked to increased fat mass children and adolescence (Worsley, 2008). Thus, overeating is encouraged by the priming effect of unheathly food advertisement.
Conversely, self-regulation can also be enhanced through priming. Another study by Papies & Hamstra (2010) demonstrated that when primed with dieting messages, restrained eaters reduced eating behaviour, while unrestrained eaters showed no effect. By being subjected to a diet reinforcing poster, restrained eaters were less likely to snack on foods provided, indicating that diet priming may provide a tool to prevent overeating.
Reduction in monitoring
The second behavioural pattern of under regulation is a reduction in monitoring of food intake. People fail to self-monitor when they experience reduced self-awareness. In narrowing attention to external factors, an individual disengages with the normal processes that inhibit eating, allowing them to overeat (Heatherton & Baumeister, 1991). Self-awareness can be reduced by a number of distractions including TV, socialisting, variety, and intoxication.
Increased television viewing has been linked to weight gain. Although, this is potentially due to a reduction in physically activity, television viewing is also related to a greater intake of energy dense foods. In a study by Blass et al (2005), individuals consumed considerably more kJ when eating in front of the TV when eating alone. While the time taken to eat a food such as pizza remained the same in both conditions, when eating in front of the TV the time between slices reduced, allowing the subjects to consume more in the same time period.
People often consume more food when they are with other people than when they are eating alone (Salvy et al., 2009) . This phenomenon may occur through subconscious modelling of other people's behaviour or through a decrease in self awareness due to conversational distractions (Vartanian et al., 2008). Interestingly some research suggests that some people consume less when in the presence of strangers, which may be a result of increase self awareness (Salvy et al, 2007).
The link between variety of foods and overeating has been researched for several decades. Variety, and the desire to sample, distract an individual from monitoring their food intake. It is clear that the greater the variety of food provided the more an individual is likely to consume (Remick et al., 2009; Rolls, et al, 1981). Brondel et al. (2009) found that food intake even increased with the simple introduction of condiments such as tomato sauce or whipped cream.
Alcohol consumption reduces self-awareness and monitoring by disinhibiting an individual. People consuming alcohol are less likely to keep track of what they are eating and are more likely to overeat (Hull, 1981). A study by Caton, Ahearn and Hetherington (2004) found that the consumption of 4 standard drinks (10g of alcohol) increased appetite and food intake in males under laboratory conditions. This observation conforms with other studies on the relationship between alcohol and overeating (Polivy & Herman, 1976).
The third behavioural pattern of under regulation is inadequate strength or willpower to act against the power of an impulse. An impulse refers to a desire to perform a particular action such as eating a particular food on a particular occasion (Baumeister et al, 1994). Stopping oneself from having a slice of cake at a birthday party is a difficult task and relies on a great deal of strength or will power. There are some recognised causes of faltering willpower including:
People are less effective at self-regulation when they are physically or mentally fatigued. Evidence of this exists in dieters, who are most likely to overeat late in the day when they are tired (Mitchell et al 1991). This trend indicates that dieting is hard work and that physiological hunger signals can build up leading to a binge in the afternoon or evening.
Many people, particularly restrained eaters, overeat when they are sad, bored or in a bad mood (Chua et al., 2004; Wallis and Hetherington, 2004). This observation has resulted in several theoretical hypotheses, including the Emotion Hypothesis and the Cognitive Investment Hypothesis. According to the Emotional Hypothesis, restrained eaters overeat in an effort to reduce distress, causing food to act as a comforter (Stroebe, 2008). The Cognitive Investment Hypothesis suggests that constant self-regulation requires cognitive resources. During times of emotional distress, cognitive resources are diverted to coping with those emotions and away from self-regulation. As a result, people’s willpower crumbles and many people overeat (Wallis and Hetherington, 2004).
The fourth and final behavioural pattern discussed by Baumeister et al (1994) is that of psychological inertia, the tendency to continue a particular behaviour once it has begun. This concept is at the heart of not being able to stop at one chocolate biscuit, or one potato chip.
In a seminal study, Herman, Polivy and Esses (1987) found that restrained eaters consumed more ice-cream than unrestrained eaters when everyone first consumed a milkshake ‘preload’. This trend to overeat once a diet has been ‘broken’ has been termed the ‘what the hell effect” or counter-regulation. Counter-regulation has been observed in several study designs.
Interestingly, the likelihood of a chronic dieter to counter regulate and overeat was dependent on the perceived energy content of the preload rather than the actual kJ content. Knight and Boland (1989) found that restrained eaters, who were told their preload was high in kJ when it was not were more likely to counter regulate. Restrained eaters who were told that their preload was low in kJ when it was in fact highly energy dense, were less likely to overeat and maintain their dietary restraints afterwards. These observations exemplify the inability of chronic dieters to detect and respond to physiological hunger and satiety cues.
|“||Gluttony kills more than the sword
Misregulation entails exerting self-control but in a way that is misguided, preventing the desired result from being achieved. Misregulation can occur because people have inadequate or incorrect knowledge and unrealistic and inconsistent standards (Baumeister et al., 1994). Prime examples of this include the increase in portion size over time and the desire to achieve the thin ideal.
Recent decades have seen an increase in the commercial serving sizes of food and drinks. What is more, the average dinner plate size has increased in response to the increases portion sizes (Wansink & Cheney, 2005). This increases causes a distorted perception of a normal serving size and encourages over-consumption of food. A study by Rolls and colleagues (2004) demonstrated that the larger the package size of potato chips, the more the individual would eat. Even those who are self-regulating can be deceived by the portions presented to them, causing unintentional overeating.
Unrealistic "thin ideal"
The struggle towards the thin ideal in women, and the muscular ideal in men, can create an unrealistic perception of one’s own body and what constitutes a healthy body. While for some restrained eaters the aim of dieting is to lower weight to a healthy level, many chronic dieters are within or below healthy weight ranges, yet still feel the need to loose weight for aesthetic reasons. This type of body dissatisfaction is a distorted perception of their own body as well as the mistaken belief that being exceptionally thin is attractive and healthy (Williams & Germov, 2008). As you have seen from the studies presented restraining, food intake not only precedes overeating but also contributes to it, potentially causing weight gain, the opposite of what a chronic dieter aims to acheive.
Although there are physiological mechanism to regulate hunger and satiety many people attempt to cognitively control their food intake. However, many people who explicitly try to control their eating through dieting, can develop self-regulatory problems. These include under-regulation through conflicting standards, reduced monitoring, inadequate willpower, and psychological inertia. Misregulation through inaccurate perceptions of standard also contributes to failure of self regulation. In being conscious of these behavioural patterns which lead to self-regulation failure, an individual can become more self aware, better able to respond to physiologial hunger and satiety cues and less likely to overeat.
- Healthy eating (Book chapter, 2011)
- Eating and emotion (Book chapter, 2011)
- Diet, weight loss, and emotion (Book chapter, 2011)
- Weight Loss (Book chapter, 2011)
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