1. Introduction

With the pursuit of the “Thinness as the Beauty Standard,” an increasing number of individuals are regulating their diets to maintain a slim figure, which has led to an upward trend in the incidence of eating disorders globally, especially among young women. Bulimia nervosa (BN) is a severe eating disorder characterized by recurrent binge-eating episodes and compensatory behaviors to prevent weight gain. And the etiology of BN is very complex, including biological factors, stress and stress, parenting styles, sociocultural factors, and personal psychological traits. Among them, willfulness, compliance, and borderline personality are the most common personality traits in BN patients [1]. In addition, the lifetime prevalence of BN is high, with a significantly higher prevalence in women than in men, which not only poses a threat to the physical health of the patients, but also frequently comorbid with a variety of mental health problems, such as depression, anxiety, and substance abuse [2]. In recent years, with an in-depth understanding of BN, Cognitive Behavioral Therapy (CBT) has been widely used in the treatment of BN and has achieved good efficacy. Thus, the paper systematically analyzes the theoretical foundations, intervention strategies, treatment effects, and implementation challenges of CBT, and makes recommendations for future research directions. CBT, which targets patients' cognitive biases and behavioral patterns to reduce binge eating and compensatory behaviors, has been shown to be an effective psychotherapeutic approach for treating bulimia nervosa.

2. The Theoretical Basis of CBT

2.1. Definition and Principles of CBT

CBT is a psychotherapeutic approach that combines cognitive and behavioral therapies, arguing that people’s thinking, emotions, and behaviors interact with each other. Its core idea is that maladaptive thinking patterns lead to emotional and behavioral problems. Recovery of mental health is achieved by helping patients identify these thoughts and transform them into more positive and adaptive thought patterns through cognitive restructuring, leading to changes in emotional and behavioral performance. Moreover, its principles include cognitive restructuring, behavioral activation, skill training, structured and goal-oriented therapeutic processes, collaborative therapeutic relationships, assessment feedback and relapse prevention, and flexibility and individualized treatment strategies. In cognitive restructuring, the therapist guides patients to identify and challenge unreasonable or negative thinking patterns, promoting individuals to understand problems from a more realistic and positive perspective. Meanwhile, behavioral activation encourages patients to try new behavioral patterns in real life, which not only helps consolidate cognitive changes but enhances individuals’ self-efficacy. In addition, CBT provides individuals with the ability to cope with life challenges through skill training, such as problem-solving, communication skills, stress management, and self-monitoring. The therapeutic process of CBT is structured, with clear stages and goals, which focuses on solving specific problems, and emphasizes the realization of goals through behavioral experiments and exercises in the current situation. The cooperative therapeutic relationship between therapist and patient is another key element of CBT, where patients actively participate and make joint decisions in the process, ensuring that the development of treatment plans can meet their personal needs. Assessment and feedback during treatment is ongoing, aiming to monitor treatment progress and adjust treatment plans according to patient responses, which not only helps to alleviate symptoms but focuses on preventing relapse, teaching individuals how to identify and deal with possible signs of relapse. Though CBT has a set of core principles and techniques, therapists will adjust flexibly according to the specific situation and needs of each patient to ensure individualized treatment and maximize therapeutic effects.

2.2. Application of CBT in Eating Disorders

In the treatment of eating disorders, CBT centers on identifying and correcting patients’ distorted cognitions about food, weight, or body shape, and reshaping a healthy mindset to reduce abnormal eating behaviors. Studies have shown that CBT is more effective than interpersonal psychotherapy in reducing behavioral and cognitive symptoms associated with eating disorders. Improvements of core behavioral symptoms of eating disorders during the follow-up period is sustained, indicating that CBT still has lasting effects after the end of treatment [3]. Enhanced Cognitive Behavioral Therapy (CBT-E) is a variant of CBT in the treatment of eating disorders, developed by Fairburn, applicable to all types of eating disorders. It is also suitable for adolescents and inpatients [4,5]. CBT-E, based on transdiagnostic cognitive-behavioral theory, proposes mechanisms to maintain the psychopathology of eating disorders, particularly the overestimation of weight and body image and its control [6]. An effectiveness study conducted by Byrne et al. showed that 66.7% of treatment completers achieved good results [7]. And Knott et al. found that 78.3% of treatment completers achieved favorable outcomes [8].

3. CBT Intervention Strategies for Bulimia Nervosa

3.1. Preliminary Assessment and Treatment Plan Development

The initial assessment of CBT for bulimia nervosa aims to fully understand the specific situation of the patient, including the patterns of binge eating, difficulties in emotional regulation, and unhealthy cognition about weight and body shape. This process involves both clinical diagnosis and a deep understanding of the patient’s personal experiences, psychological state, and treatment expectations, laying the foundation for personalized treatment plans [9]. Preliminary assessment usually includes detailed medical history taking, mental status examination, and the use of standardized assessment tools, such as the Eating Disorders Examination (EDE) questionnaire, to assess the severity of the patient’s binge eating, purging behaviors, weight, and body image concerns. In addition, therapists pay attention to the patient’s emotional state, such as depression and anxiety levels, and potential comorbidities (clinical perfectionism, low self-esteem, difficulties with emotion regulation, and interpersonal problems) [1]. It has been found that that patients with BN exhibit higher levels of attachment-related anxiety and avoidance, and higher levels of emotional regulation difficulties [10]. Thus, special attention needs to be paid during the assessment process to the patient’s emotional state and how they cope with stress and negative emotions in their lives, which can directly affect the development of treatment strategies. Therapists and patients work together to develop a targeted and individualized treatment plan based on the results of the initial assessment.

3.2. Cognitive Restructuring Techniques

Cognitive restructuring is one of the core technologies of CBT, where patients can learn to replace their original cognitive biases with more positive and realistic ways of thinking. The effectiveness of CBT has been found to lie in its ability to target and address an individual’s negative automatic thoughts, especially those related to food, weight, and self-worth, which are often the triggers of bulimic behavior [11]. Research on the maintenance factors of bulimia nervosa also points out that the core of maintaining bulimia nervosa is the distortion of the function of evaluating self-worth. Patients tend to evaluate themselves largely, if not exclusively, on the basis of their weight, size, and eating habits, and actively pursue controlled eating and thinness [12]. In CBT, therapists guide patients through a series of steps to cognitive restructuring. In this process, the therapist identifies the negative, automatic thoughts associated with binge eating behavior, and then assists the patient in critically evaluating the legitimacy of these thoughts by posing inquiries such as, “Is this notion genuinely valid?” “Does evidence exist to substantiate or refute this assertion?” The patient is taught to develop more positive and realistic alternative thought patterns, such as reframing perceptions through self-compassionate statements, for example, “Even if I ate a little extra today, it does not mean that I am a failure; everyone loses control at times.” Ultimately, patients must practice and apply these new thought patterns in their daily lives to reduce the adverse effects of negative thoughts on their behavior and reinforce these new thinking habits through practice.

3.3. Behavioral Change Strategies

CBT includes a range of behavior change strategies, such as self-monitoring, exposure and response prevention, that are designed to help patients control and reduce binge eating behaviors and cope with the anxiety and stress associated with eating. Self-monitoring is a behavioral change technique in CBT, which requires patients to record their eating patterns, emotional states, and situations that trigger binge-eating behaviors. Through self-monitoring, patients can more clearly recognize their behavioral patterns and work with therapists during treatment to analyze these patterns, thus finding ways to improve. Exposure and Response Prevention (ERP) is a core CBT technique that requires patients to confront situations that trigger binge-eating but does not allow for purging behaviors, such as self-induced vomiting or excessive exercise. Through this approach, patients gradually learn to handle inner fears without purging behaviors, reducing anxiety about food and weight. However, the implementation efficiency of ERP is affected by the degree of patients’ resistance to exposure and the therapist’s skills. Therefore, therapists usually adopt progressive exposure according to the patient’s situation, starting with less threatening situations and gradually increasing the difficulty to help patients gradually adapt [3].

4. The Effectiveness of CBT Treatment for Bulimia Nervosa

4.1. Quantitative Analysis of Treatment Effects

Quantitative analysis is key to validating the efficacy of CBT. The research has pointed to the use of standardized psychological scales to assess patients’ symptom changes before and after treatment as an important measure of CBT efficacy [13]. For example, the Eating Disorders Inventory-2 (EDI-2) and the Eating Disorder Examination Questionnaire (EDE-Q) are used to quantify patients’ sense of control over food, perception of weight and body shape, and changes in eating behavior are widely adopted methods currently. The scales reflect not only changes in patients’ self-perceptions but also adjustments in their behavioral patterns, providing a comprehensive assessment of the intervention effects of CBT. In addition, after CBT treatment, patients’ ED Symptom Scale scores decreased notably, indicating that CBT is effective in reducing binge eating behavior and related symptoms [14]. In particular, CBT strategies targeting emotion regulation and cognitive restructuring were significantly effective in reducing patients’ mood swings and improving their perceptions of food and weight. The findings further confirm the centrality of CBT in the treatment of bulimia. While the overall efficacy of CBT has been widely recognized, factors such as individual differences, therapist skills, treatment standardization, and patients’ resistance to exposure therapy. Therefore, quantitative analyses show the variability of CBT treatment outcomes, underscoring the necessity to consider individual factors during implementation and the significance of ongoing evaluation and adjustment of the treatment process.

4.2. Qualitative Assessment of Patient Experience

The use of quantitative data alone is often inadequate for fully reflecting the psychological changes and subjective experiences of patients. Qualitative assessment, as a supplementary research method, can reveal the subtle processes of patients’ personal feelings, attitude changes, and behavioral adjustments during the CBT process through in-depth interviews, observations, and self-reports. Research has shown that in the treatment of bulimia nervosa, the patient's internal world, including complex emotions about food, fear of weight, and self-evaluation, is a central focus of CBT interventions [15]. Not only does it show the impact of CBT on an individual, but it also facilitates comprehension of the rationale behind the efficacy of specific strategies for particular patients. This information is of great value for the formulation and improvement of personalized treatment plans. For example, patients may indicate an enhanced sense of self-efficacy and agency with regard to their eating behaviors during the course of treatment. They may discuss the ways in which their cognitive restructuring and behavioral change strategies can help them cope with the stresses and challenges of daily life. Patient acceptance of exposure and response prevention is a key aspect of qualitative assessment. It is found that though ERP is effective in reducing binge-eating and purging behaviors, patients may feel fearful and resistant to being directly confronted with the situation that triggered the binge. Through interviews, therapists can learn about patients’ different reactions to exposure and how they gradually adapt to and overcome these fears during the treatment process. Understanding these processes helps therapists adjust exposure strategies, reduce patients' anxiety, and thereby improve the feasibility and acceptance of treatment.

5. Challenges and Responses in the Implementation of CBT

5.1. Therapist Competence and Training

The professional competence and training level of therapists are crucial to the effectiveness of CBT treatment. It is widely recognized that treatment outcomes depend more on individual differences in therapists than on any particular therapeutic technique or school of therapy [16-17]. First, therapists need a deep theoretical foundation, proficiently master various CBT techniques, including exposure and response prevention, cognitive restructuring, and emotional regulation. They need to understand the theoretical principles and learn to deploy them in a flexible manner to meet the specific needs of each patient, maintaining a high sensitivity to patients’ individualized treatment needs. Second, therapists should have excellent interpersonal communication skills to build trust and cooperation in the treatment process. Their empathy and the way they handle patient resistance or mood swings directly affects patient engagement and treatment outcomes. Third, therapists should review the treatment process when providing CBT-BN or CBT-E, and should maintain sensitivity and clinical judgment when understanding and applying rehabilitation standards. This enables them to better understand the patient’s behavioral patterns and provide an individualized treatment plan for the patient [18-19]. In addition, therapists should receive specialized training in the treatment of eating disorders, such as learning about specific treatment modalities such as CBT-E or CBT-BN and how to assess and manage patients’ emotional and behavioral risks, and should also learn to work with a multidisciplinary team, such as collaborating with dietitians, psychiatrists, and family therapists to develop and implement treatment plans.

5.2. Patient Compliance and Motivation

Patient adherence and motivation are key factors that influence the efficacy of CBT. Adherence refers to the degree to which the patient follows the treatment plan, including attending therapy sessions, completing homework assignments, and practicing new skills, while motivation is the intrinsic drive to actively participate, overcome difficulties, and persist in change. These two factors are inextricably linked and together constitute the foundation for successful treatment outcomes. It has been noted that patients’ initial resistance, skepticism, and indecision about treatment outcomes are often major barriers to adherence to CBT [20]. In addition, patients’ treatment expectations, their level of trust in the therapist, and their beliefs about change can also affect adherence. Patients with high expectations are prone to disappointment when challenged, while patients with low trust may question the treatment, which in turn reduces adherence.

Motivation is categorized into internal and external motivation. External motivation may come from pressure from family, friends, or doctors, or from the influence of social expectations. Internal motivation stems from the patient’s own desires, such as improving quality of life or resolving psychological problems, which is a more effective predictor of treatment outcome as it provides more sustained motivation to maintain a positive attitude and overcome treatment difficulties. To improve patient compliance and motivation, a supportive and understanding treatment environment should be created. Moreover, patients should be educated to better understand the principles and process of CBT to increase their acceptance of the treatment. Specific and achievable goals should be set for patients to increase their participation. Providing positive feedback during the treatment process can increase their confidence and motivation, and setting realistic and achievable short-term goals and praising every progress can continuously stimulate patient’s intrinsic motivation, thereby increasing their adherence to treatment [14].

5.3. Recurrence and Dropout

One of the main challenges faced by patients with bulimia treated with CBT is relapse of bulimic behavior and dropout, a problem that is particularly acute in the early stages of treatment. Patients’ mood swings and questioning of treatment goals when first confronted with the core problem often lead to the reoccurrence of binge eating behavior. Relapse of bulimic behavior usually stems from patients' frustration and persistent concerns about their self-image during treatment, suggesting that emotion management and self-identity remodeling are important in therapy [15]. To consolidate the effects of treatment and prevent relapse, a number of long-term strategies need to be adopted after treatment has ended. First, continuous self-monitoring is important. Patients should keep track of their eating, mood and behavioral patterns so that potential signs of relapse can be identified and addressed in a timely manner. Second, regular review of coping strategies acquired during treatment helps to skillfully apply them in times of stress or challenge. Moreover, utilizing established support networks, including family, friends, and professional groups, can provide patients with ongoing emotional support and information exchange.

Another challenge is dropout, where patients abandon treatment midway due to disappointment with the outcome, fear of continuing treatment, and interference from other stressors in their lives. The gap between high expectations at the beginning of treatment and the actual slow progress is a common reason why patients drop out [21]. When patients realize the deep-seated problems they have to face during the treatment process, they may feel psychological discomfort, which may lead to avoidance tendencies. In response to possible midway problems, the following strategies have proven effective: first, identifying and addressing potential barriers is crucial, by working closely with patients to identify factors that may lead them to abandon treatment and exploring solutions together. Second, enhancing a sense of meaning in treatment is key to motivating patients to adhere to treatment. Helping them recognize the long-term benefits of treatment and its positive impact on quality of life can enhance engagement and commitment to treatment. Finally, providing flexible treatment scheduling can also help to reduce dropout rates, and dropouts due to scheduling conflicts can be minimized by adapting treatment times to fit patients' lifestyles and schedules. With these strategies, the likelihood of patients completing their treatment plans can be significantly increased, thereby maximizing treatment outcomes.

6. Conclusion

The paper fully explores the theoretical basis, intervention strategies, efficacy, and implementation challenges of cognitive behavioral therapy (CBT) in the treatment of bulimia nervosa (BN). As a well-targeted psychological intervention, CBT significantly reduces binge eating and compensatory behaviors and ameliorates patients’ excessive concern about weight and body size by adjusting their cognitive biases and behavioral patterns. Studies have confirmed that CBT is not only effective in relieving BN symptoms, but also improves patients’ emotional regulation, self-management skills, and coping strategies, thereby improving their quality of life overall. Nevertheless, there are many challenges in the implementation of CBT, such as relapse during treatment, patient dropout, and the impact of therapist professionalism on efficacy, which often limit the sustainability and wide applicability of treatment effects. Therefore, how to improve therapists’ professional competence and enhance patients’ adherence and motivation has become crucial to the efficacy of CBT. To reduce patient dropout rates, providing flexible treatment arrangements, enhancing the meaning of treatment, and establishing a supportive therapeutic environment are all essential strategies.

In the future, CBT research and application should be further developed towards personalization and diversification. In particular, there is a need to develop adapted versions of CBT for patients with different cultural backgrounds, age groups, and specific symptoms. Meanwhile, exploring the integration of CBT with other therapeutic approaches (e.g., interpersonal psychotherapy, dialectical behavioral therapy, family therapy, etc.) may provide a more comprehensive therapeutic effect that meets the multilevel needs of patients. This multimodal and integrated treatment program is expected to bring hope for recovery to more patients while further enhancing the therapeutic effects of BN.