Personality and Obesity
Personality traits are characteristic ways of thinking, feeling, and behaving. Obesity is defined as a body mass index (kg/m2) ≥30.
Personality traits are regularly implicated in consequential health outcomes. Obesity (body mass index ≥30) is a significant health issue worldwide that may contribute to poor health. Obesity is also socially undesirable and associated with discrimination and worse social and psychological outcomes. The characteristic ways of thinking, feeling, and behaving that are captured by broad personality traits may contribute to the development of obesity across the lifespan.
Overview of Personality and Body Weight
The World Health Organization estimates that approximately 39% of the world’s adult population is overweight and 13% is obese (see http://www.who.int/mediacentre/factsheets/fs311/en/). In the United States and other Western countries, the rate is considerably higher, with about a third of adults measuring in the obese weight category. Many factors contribute to the risk of obesity, from genetics to public policy. Within the psychological domain, the traits that define the five-factor model (FFM) of personality have been associated with both body mass index (kg/m2) and risk of obesity (BMI ≥30).
Conscientiousness, the tendency to be organized and disciplined, is the personality trait with the most consistent association with BMI and risk of obesity. Individuals who score higher in Conscientiousness tend to have lower BMI and are less likely to gain excess weight over time (Jokela et al. 2013). This association has been found in samples across the adult lifespan, from young adulthood (Sutin and Terracciano 2016a) to old age (Sutin et al. 2011). In addition, similar associations have been found for traits related to Conscientiousness in childhood and obesity risk in adulthood. Children who have better delay of gratification skills at age 4, for example, are at lower risk of obesity 30 years later (Schlam et al. 2013). Conscientiousness has been associated with lower BMI across a number of different cultural contexts, including the United States, Australia, Italy, Estonia, Israel, and Mexico. Such consistency suggests that this association is universal, although there is some evidence that culture may shape the association between Conscientiousness and body weight (Sutin et al. 2015).
Neuroticism is also associated with greater risk of obesity and weight gain: individuals who have a tendency to experience negative emotions and vulnerability to stress tend to weigh more and are at greater risk of obesity (Magee and Heaven 2011). This association is less consistent than for Conscientiousness and may be due to differences in the content of the personality measure used. That is, Neuroticism is a heterogeneous trait, and specific aspects of it (e.g., impulsiveness) may be more relevant for BMI than other aspects (e.g., anxiety). As such, short measures of Neuroticism may miss the components of this trait that increase vulnerability to weight gain and obesity. Still, there is growing evidence that this trait is relevant for body weight and obesity risk and that related constructs, such as depressive symptoms, have similar relations with BMI (Luppino et al. 2010).
The association between Conscientiousness and Neuroticism and obesity is mediated by both behavioral and physiological mechanisms. Individuals who score higher in Neuroticism and lower in Conscientiousness tend to eat less healthy meals, eat at irregular intervals, and overeat to the point of feeling ill (Sutin and Terracciano 2016b). Individuals with these traits also tend to engage in more sedentary behavior and are at greater risk of being physically inactive (Sutin et al. 2016). These behavioral factors explain part, but not all, of the association between Neuroticism/Conscientiousness and BMI (Sutin and Terracciano 2016b). In addition to this behavioral pathway, Neuroticism and Conscientiousness have been associated with biomarkers that increase risk of weight gain. Lower Conscientiousness, for example, has been associated with higher levels of circulating C-reactive protein, a marker of inflammation that increases risk of weight gain (Luchetti et al. 2014). Lower Conscientiousness has also been linked to higher levels of leptin, an adipose-derived hormone that regulates satiety. Leptin mediates the association between Conscientiousness and body mass index, which suggests that in addition to being less receptive to external signals, individuals low in Conscientiousness are also less sensitive to internal signals of satiety (Sutin et al. 2013b).
Evidence from longitudinal studies suggests that the association between personality and BMI might be bi-directional. Traits such as Conscientiousness increase risk for the development of obesity over time (Jokela et al. 2013). Conscientiousness and Neuroticism have likewise been associated with greater fluctuations in weight over time, which suggests that these traits are important for weight regulation (Sutin et al. 2011). Although BMI tends to be unrelated to change in the five major dimensions of personality, significant change in body weight is associated with specific aspects of trait development. Data from two longitudinal studies indicate that individuals who gained at least 10% of their baseline body weight over 10 years also increased in the tendency to give in to cravings (i.e., impulsiveness, an aspect of Neuroticism) and increased in the tendency to think before acting (i.e., deliberation, an aspect of Conscientiousness; Sutin et al. 2013a). These findings suggest that individuals are not gaining weight mindlessly and may be aware of their actions, but their emotional impulses may be too hard to overcome.
In contrast to Conscientiousness and Neuroticism, there is less evidence that the other three FFM traits are associated with obesity. Interestingly, Openness is consistently associated with healthier patterns of eating and physical activity, but it tends to be unrelated to BMI. Individuals who score higher on this tendency to be creative and unconventional eat more fruits and vegetables and adhere to a Mediterranean diet (Mõttus et al. 2013) and engage in more frequent physical activity (Wilson and Dishman 2015). These healthy behavioral patterns, however, apparently do not translate into lower body weight for these individuals. Similar to Openness, Extraversion, the tendency to be sociable and outgoing, is associated consistently with greater frequency of physical activity (Sutin et al. 2016) but tends to be unrelated to BMI. There is some evidence that sex moderates the association between Extraversion and BMI, with a positive association among men and no association among women (Brummett et al. 2006). Finally, Agreeableness, the tendency to be trusting and modest, tends to be unrelated to BMI and risk of obesity (Jokela et al. 2013).
An individual’s characteristic ways of thinking, feeling, and behaving contribute to body weight and the risk of obesity through both behavioral and physiological mechanisms. Obesity may further be one mechanism that contributes to the relation between personality and health outcomes across the lifespan.
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