Approximately 1.9 billion adults globally are currently living with overweight and 650 million with obesity . Much of the literature examining the incidence of obesity has focused on lifestyle factors, including a poor diet and a lack of physical activity, as the leading causes of weight gain . However, interventions which focus on lifestyle factors alone are often unsuccessful long-term, with evidence indicating that approximately 80% of people living with overweight do not maintain a weight loss of ≥ 10% of total body weight for more than a year . A meta-analysis of 45 studies examining the effectiveness of diet and exercise interventions found that the implementation of these interventions only had a small effect on long-term weight loss in adults . These findings suggest that lifestyle only interventions are unlikely to lead to sustained weight loss among people living with overweight or obesity. Other evidence suggests that socioeconomic adversity and psychological experiences may also contribute to the development of overweight and obesity , but further research is needed to understand their impact on weight gain from childhood through to adolescence and adulthood. Obesity appears to be a complex, multifactorial health condition, where there are wide-ranging, interconnected factors that can lead to weight gain and thus obesity, with many of these factors either outside or partially outside of an individual’s control . Examples of other factors that are associated with an increase likelihood of overweight or obesity during adulthood, include extent of socioeconomic deprivation and negative psychological experiences during childhood .
Evidence suggests that psychosocial risk factors, such as traumatic experiences during childhood, may increase the risk of developing obesity during adulthood [7–9]. A theoretical model of obesity causation has been proposed by Hemmingsson , which identifies how a series of negative psychosocial events may occur during childhood/adolescence and consequently lead to the development of overweight or obesity in adulthood. For example, when a child experiences a high degree of psychological and emotional stress, this may lead to overconsumption of calorie-dense foods (i.e., junk food) as a maladaptive coping mechanism in response to the stressful life events. When left unaddressed, negative psychosocial experiences and the ongoing consumption of unhealthy food can significantly increase the risk of developing overweight and obesity. This process of weight gain is often influenced by stressors in the social environment which can lead to an increased release of hormones such as cortisol, resulting in a subsequent increase in appetite and desire for calorie-dense foods [10, 11]. Negative coping mechanisms, such as overeating, are often maintained in an attempt to cope with the continued exposure to psychosocial stressors, which often leads to greater weight gain and also increases the risk of bullying, low self-esteem, and the development of psychological disorders, which can be exacerbated by the presence of weight stigma . Therefore, each stage of this model has the potential to reinforce a previous stage in a negative feedback loop, which can have a significant physiological and psychological impact on an individual living with overweight or obesity . Recent research has identified that different forms of childhood trauma (i.e., emotional, physical, sexual) may be primary risk factors that contribute to the development of overweight and obesity during adolescence and early adulthood .
Childhood trauma can have a detrimental impact on the psychological and physiological development of children and adolescents . For instance, evidence shows that childhood trauma can increase the risk of depression, anxiety, PTSD  and eating disorders . In addition, childhood trauma can significantly affect brain development and function, including areas of the brain associated with the regulation of stress . Due to this reduced capacity to manage stress, individuals who have experienced childhood trauma may be at an increased risk of substance abuse disorders, including the use of alcohol and illicit drugs to cope with negative emotions . Other coping strategies to manage negative emotions, such as overeating, are also more common in those who have experienced childhood trauma, which can increase the likelihood of developing obesity in adulthood [13, 18]. Several extensive meta-analyses show that individuals are significantly more likely to develop obesity during adulthood if they have previously experienced childhood trauma [7–9, 19]. However, while the evidence suggests that childhood trauma is associated with obesity, the underlying mechanisms involved in this relationship are not yet known.
Food addiction may contribute to the relationship between childhood trauma and the development of obesity during early adulthood . Food addiction is described as the inability to control the consumption of favourable foods, particularly processed foods containing additional sugars and fats (i.e., junk food), through mechanisms similar to those which underlie substance addiction . Emerging research has shown that several biological and behavioural changes occur in those with food addiction, such as differences in brain reward processes, which result in impaired control and the development of tolerance and withdrawal symptoms . These notable changes which occur in those with food addiction are similar to those found in individuals with substance abuse/addiction disorders , suggesting that similar mechanisms may be involved in the development and maintenance of food addiction . A primary consequence of food addiction is weight gain and evidence from a large meta-analysis (N = 196,211) shows that compared to adults living with a healthy weight, adults living with overweight or obesity are more than twice as likely to report symptoms of food addiction . While the development of overweight or obesity may be an obvious consequence of food addiction, the relationship between food addiction, childhood trauma, and overweight or obesity is less clear.
Few studies have examined the relationship between childhood trauma and food addiction. A preliminary study showed that food addiction may be associated with several subdomains of childhood trauma, including emotional, physical, and sexual abuse, as well as emotional and physical neglect . This study sampled 231 adults and found small to moderate effect sizes between these subscales of childhood trauma and food addiction . However, this study recruited outpatients from an eating disorders clinic, which may limit the external validity of these findings. Similarly, another study found that an increased severity of childhood trauma was correlated with a significantly higher risk of developing food addiction in a sample of female nurses; severe childhood trauma was associated with an approximately 90% increase in food addiction risk . A different study found that those who had experienced childhood trauma were more likely to have severe food addiction symptoms, in a group of participants who were seeking bariatric surgery . However, the external validity of these studies was also limited, as the samples recruited were not representative of the general population [25, 26].
While these studies report methodological limitations regarding recruitment, a recent study has demonstrated the relationship between food addiction and childhood trauma in a non-clinical sample . This study recruited 186 participants (84 males and 102 females) who did not have any diagnosed psychiatric or medical conditions, reporting that in participants with high BMI (> 25kg/m2), food addiction was significantly correlated with early life adversity. This relationship between food addiction and childhood trauma, may explain the association between childhood trauma and obesity, as food addiction is significantly associated with higher BMI scores . However, no study to date has examined the role of food addiction in the relationship between childhood trauma and obesity development. Therefore, the aim of this study is to explore the potential mediating role of food addiction in this relationship. The following hypotheses are proposed:
Childhood trauma will be significantly and positively associated with BMI.
Childhood trauma will be significantly and positively associated with food addiction.
Food addiction will be significantly and positively correlated with BMI.
Food addiction symptoms will significantly mediate the relationship between childhood trauma and BMI