Weight fluctuates for many people, but severe fluctuations that become long-term problems have a few theoretical causes. As of 2016, according to the World Health Organisation, around 1.9 billion adults across the world were overweight, and 650 million were obese. So, what is the definition of obesity according to psychology?
Psychological Explanations For Obesity: Physical And Psychological Effects
Body mass index (BMI) is a measurement that divides a person's weight by the square of their height, giving a number that classifies them into one of these categories: underweight, normal weight, overweight, or obese. However, BMI measures body mass and can't differentiate between muscle and fat. Because of this, some athletes may be classified as obese due to their muscle mass. So, we can see some inherent issues with using BMI to measure health.
Obesity is defined as having too much body fat or a BMI greater than 30.
Obesity is at the upper end of the weight scale. Those significantly over a healthy weight are considered to be obese, and this can have various serious negative effects on health.
Obesity can have various effects on your body and health, which can be both physical and psychological. Physical effects of obesity can include:
- Type II diabetes
- Cardiovascular diseases (heart disease and stroke)
- Hypertension
- Reproductive complications
- Cancer
- Sleep apnea
- Gallstones
- Low energy
- Difficulties performing physical activities
- Difficulties travelling
Psychological effects of obesity can include:
- Mental illnesses
- Depression
- Anxiety
- Stress
- Eating disorders
- Low self-esteem
- Low self-confidence
- Difficulties at work
- Difficulties in relationships with family
- Difficulties in relationships with friends
- Difficulties in romantic relationships
The latter four can then affect mental health.
Figure 1. There are different causes and effects of obesity.
Psychological explanations for obesity: Psychological causes
Several psychological explanations for obesity suggest different ways obesity is caused. These explanations include cognitive, behavioural, environmental, and social factors.
Keys et al. (1950) conducted research on WWII soldiers and drew some interesting conclusions. They had American soldiers who had no interest in fighting start a starvation diet. These soldiers were already 'conscientious objectors' because of their unwillingness to fight. Then, when they started the diet, the more they were denied food, the more they thought about it. This indicated to Keys et al. that the more restricted one's eating becomes, the more one thinks about food, thereby turning into a risk factor for obesity.
The three main psychological explanations of obesity are:
- Restraint theory
- Disinhibition
- The boundary model
These theories are briefly mentioned as an overview but are explained in more detail with evaluation in separate sections.
Psychological Explanations For Obesity: Restraint Theory
Restraint theory is a cognitive theory of obesity developed by Herman and Polivy (1975). Since trying to lose weight involves restraining one's eating through types of food and amounts of food, Herman and Polivy suggested that restrained eating is a self-defeating practice, since many people who do this don't succeed in losing weight. This even goes to the extent of some people becoming obese. Two factors are part of restraint theory: cognitive control and paradoxical outcome.
Cognitive control
Restrained eaters set strict limits on themselves by categorising foods as 'good' and 'bad', 'forbidden' and 'allowed', and the specific amounts of food they need to lose weight. This restricted diet is a way of forcing control in a highly organised manner, which obese people believe is the way for losing weight.
Since the person will be thinking about eating and losing weight the whole time, the control is cognitive.
Paradoxical outcome
Whilst there is increased control of overeating, this doesn't mean that the person will be able to lose weight successfully. The person is often more preoccupied with food due to thinking so much about what they can and can't eat. Due to this cognitive control, the restrained eater doesn't eat when their body signals that they're hungry, nor stops eating when their body signals fullness. This leads to disinhibition of eating behaviour.
Psychological Explanations For Obesity: Disinhibition
Restrained eating isn't the only cause of obesity; just how it starts. When disinhibition comes into play, it forms a dysfunctional cycle along with restrained eating.
Disinhibited eating is a period of time that follows restrained eating, in which the obese person eats as much as they want.
After a period of restrained eating, they get tired of restricting themselves and start eating as much as they want, often taking an 'all or nothing' approach. All or nothing is when the person believes that once they start to overeat or eat food they consider 'bad', they continue doing so because they think they might as well eat everything as they have already failed.
Disinhibited eating starts by being influenced by food cues that are internal (e.g. mood) and external (e.g., smells - environmental trigger, and media images - social trigger). Such cues are called disinhibitors, and they lead to a loss of control over restrained eating. This can even lead to a period of binge eating in some cases.
Psychological Explanations For Obesity: The Boundary Model
Food intake lies on a continuum ranging from feeling hungry to feeling full/satiated. Different biological processes determine how much and when we eat on each end of this continuum.
When we feel low energy levels, the body feels an aversive state of hunger, motivating us to eat. When we feel full, there's an aversive feeling of discomfort, which motivates us to stop eating.
Therefore, eating starts at the boundary of hunger and ends at the boundary of fullness/satiety. Between these two boundaries is a space of biological indifference, in which there is the minimal influence of biological processes. This is where we are neither hungry nor full, and cognitive or social factors affect our eating behaviour.
Restrained Eaters
Restrained eaters have a lower hunger boundary, so they are less responsive to these feelings when they feel hungry. But they also need more food to feel full because they have a higher satiety boundary. Therefore, the zone of biological difference is longer, meaning their eating is more time under cognitive than physiological control. This makes them more susceptible to disinhibition effects.
Restrained eaters have a self-imposed satiety boundary (below the biological satiety boundary), which they set as the maximum amount they want to eat. However, when they break the self-imposed boundary of their diet, they eat way past the biological satiety boundary. As mentioned beforehand, this leads to a passive and resigned 'all or nothing' approach.
Restraint theory fails to acknowledge those who successfully diet through restrained eating, and people with anorexia may overeat/restrict their eating without becoming obese.
Psychological Explanations For Obesity: Psychological Interventions
There are different psychological interventions for obesity, but the most common is cognitive behavioural therapy (CBT). This includes goal-setting, self-monitoring, stimulus control, substituting behaviours, and restructuring cognitions. Many studies have found that CBT has successfully reduced patients' weight who had the treatment (Fabricatore, 2007).
Psychological Explanations For Obesity - Key Takeaways
- Obesity is defined as having too much body fat or a BMI greater than 30.
- The three main psychological explanations of obesity are restraint theory, disinhibition, and the boundary model.
- Restraint theory is a cognitive explanation of obesity that suggests obesity is a paradoxical outcome of attempted restrained eating.
- Disinhibition is a lack of control over restrained eating, leading to overeating or binge eating.
- The boundary model explains that since restrained eaters are less responsive to feelings of satiety, they require more food to feel full and eat too much when they pass their self-imposed satiety boundary is broken.
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