Prevalence and consequences of obesity
The prevalence of obesity in the Netherlands increased 6-fold in the period 1980–2009 in boys (0.3% to 1.8%) and 4.5-fold in girls (0.5% to 2.2%) . Generally, when there is an increase in prevalence of obesity, there is a greater relative increase in severe obesity .
Childhood and adolescent obesity are associated with serious comorbidities including type 2 diabetes mellitus, hyperlipidemia, hypertension, respiratory and musculoskeletal conditions and liver abnormalities [3–5]. The increase in obesity-associated diseases leads to a significant increase in direct and indirect medical costs . In addition to physical health problems, obese children and adolescents also are more likely to suffer from a variety of psychosocial problems [7–9]. They are more likely than non-obese children to be a target of societal stigmatization, including teasing and bullying [10, 11], to be socially isolated [5, 12], to have relatively high rates of disordered eating, anxiety, and depression , and to suffer from suicidal thoughts and making suicide attempts . When they reach adulthood, they are less likely than their thinner counterparts to complete college and more likely to live in poverty . They are also less likely to get married . A further illustration that obesity has a large impact on young people’s lives is reflected in the finding that severely obese children and adolescents reported to have similar quality of life as those diagnosed with cancer [14, 15]. Therefore adequate management of severe childhood obesity may contribute to reduce their current and future social, psychological and physical impairment.
Intensive combined lifestyle interventions
It is generally recognized that the more severe forms of obesity may well warrant more intensive therapeutic interventions  than less severe obesity . Because regular outpatient treatment appears to be insufficiently effective for the specific patient group of severely obese children and adolescents [18–20], it has been proposed that there is a need for experienced, specialized pediatric obesity centers that can provide intensive treatment by a multidisciplinary team with expertise in childhood obesity and its comorbidities [18–20]. According to several guidelines, the treatment team should include a physician, dietician, exercise specialist and psychologist or other mental health care provider that is able to offer behavioral counseling [17–22].
A promising alternative to regular outpatient treatment is so called “immersion treatment” that places patients in a therapeutic and educational environment for extended periods of time, for example a residential summer camp or inpatient setting [21, 23]. Immersion programs described in a recent review included the components controlled diet, physical exercise/activity, nutrition education and therapy and/or education regarding behavior change. The participants in the reviewed treatments that included a follow up lost an average of 23.9% of their overweight during treatment and 20.6% pre-immersion to follow up (ranging from 4 months to 3.6 years later) . Inclusion of cognitive behavioral therapy (CBT), defined as including “regular group and/or individual meetings with a therapist utilizing CBT techniques for managing behavior change, such as self-monitoring, motivational interviewing/decisional counseling and problem-solving”, seems especially promising, resulting in an average of 29.9% loss of overweight in total at follow-up, compared to 9.4% for programs without cognitive behavioral therapy .
Heideheuvel (part of Merem Treatment Centers) is a specialized clinic in the Netherlands offering a form of immersion treatment, by means of an intensive inpatient combined lifestyle intervention, focusing on nutrition, physical activity and behavior change of the severely obese participants and their parents. Improving self-regulation of eating behavior is one of the main goals of the treatment at Heideheuvel. The clinic uses cognitive behavioral techniques to improve self-regulation.
Although the need for combined lifestyle interventions targeting nutrition, physical activity and behavior change is widely acknowledged, long-term follow-up studies of obesity interventions are lacking, especially for severely obese youth [17, 24, 25].
According to Yanovski and Yanovski the known long-term results for children and adolescents are generally disappointing, because the weight reduction is often not maintained . However, there appear to be remarkable individual differences in treatment success . For some patients treatment is highly successful, while others continue to gain weight despite treatment. This raises the question what determines inter-individual variability in intervention success.
Currently there is little insight in the psychosocial factors that may be crucial in determining the long-term outcome. The ability to self-regulate dietary intake has been proposed as an important factor in weight loss and weight loss maintenance [8, 27–32].
The role of self-regulation
Severe obesity results from a sustained chronic positive energy balance. This implies that there is an underlying inability to regulate food intake in such a way that it matches energy expenditure. Volkow and others have postulated that this inability to regulate food intake can be seen as a brain-related dysfunction whereby reward-driven urges for food override the cognitive ability to limit food intake . Especially children and adolescents are vulnerable to problems arising due to self-regulatory failure, because the neurocognitive structures that link reward systems to the executive control system are still in development . The inability to self-regulate is particularly problematic for children who are overwhelmed with an abundance of food and food cues due to their socio-economic and cultural environments or who grow up in families where the parents have insufficient parenting skills to teach their children self-regulation in response to food cues .
Self-regulation encompasses any, conscious and non-conscious, efforts by people to alter their thoughts, emotions, attention, impulses and behavior  in the service of attaining and maintaining personal goals . Self-regulation reflects the ability to resist immediate rewards (e.g. a chocolate cake) in the face of long-term goal pursuit (e.g. losing weight and maintaining the weight loss) . It is known that people differ greatly in their ability to self regulate .
Not many studies examined self-regulation of food intake in obese individuals, but the few studies that did consistently showed that obese people generally are less able to self-regulate than lean people [27, 28, 40, 41].
Two distinct aspects of self-regulation that are particularly relevant to controlling food intake, are sensitivity to reward and inhibitory control [40, 42, 43]. Sensitivity to reward is associated with the mesolimbic dopamine system . It reflects the sensory pleasure associated with the reward and the motivation to obtain the reward. Inhibitory control is regulated by the prefrontal cortex, and refers to the executive function by which impulses or responses are controlled [43, 44].
Research has indeed indicated that food is more rewarding for overweight children than for lean children, making it therefore harder for them to resist food temptations and possibly increasing the chance of excessive food intake and resulting further weight gain [45, 46]. Obese children are found to have a higher sensitivity to reward and less response inhibition than lean children [29, 41, 47–52]. For example, Nederkoorn and colleagues showed that obese children had lower levels of inhibitory control as assessed by a behavioral measure for disinhibition and were more sensitive to reward as assessed by a response preservation measure than leaner children . Above these cross-sectional studies, prospective studies showed that differences in ability to self-regulate were related to weight gain. For example Francis and colleagues showed that children who were less able to self-regulate at ages 3 and 5 years, as measured with behavioral laboratory tasks, had a more rapid weight gain from age 3 to 12 years .
Poor self-regulation, as measured with various questionnaires and behavioral measures, has also been shown to predict less weight loss, less weight loss maintenance or more attrition to weight loss programs [27, 28, 30, 40, 53]. For example, those obese children participating in a cognitive behavioral treatment program who showed relatively little inhibitory control lost less weight than those who exhibited higher levels of control .
Three decades ago Bonato et al. already suggested that interventions for obese children should aim at improving self-regulation of eating . More recent research indeed indicates that self-regulation of eating can be improved through behavioral treatment. For example, Israel et al. evaluated an intervention for overweight children and their parents that aimed to improve self-regulation in children in order to lose weight. Training components included instructions for goal setting, formulating and implementing a plan to change behavior, self-evaluation, self-reward and training in problem-solving behaviors appropriate for high-risk or tempting situations. The results indicated that improving self-regulation can help to maintain long term weight loss . Bryant et al. also indicated in a review that disinhibition in eating behavior can be successfully diminished through application of behavioral therapy aimed at self-regulation of eating behavior .
In sum, relatively poor self-regulation is likely to contribute to the development of obesity as well as to a lower amount of long-term weight loss as a result of treatment. Therefore, studying the role of self-regulation in the effectiveness of weight loss therapy may contribute to the development of more successful interventions . The main objective of this study is to determine whether the ability to self-regulate predicts long-term weight loss in severely obese children and adolescents. To our knowledge, such studies have not been performed in severely obese children and adolescents.
The potential moderating role of other psychosocial factors
An additional objective of this study is to identify other psychosocial factors that may modify the relation between the general ability to self-regulate and long-term weight loss in severely obese children and adolescents. Gaining understanding in moderating factors is important as it might help to improve tailoring interventions to children. The following factors that plausibly play an important role will be assessed:
Competence, in this study operationalized as general self-efficacy and self-worth.
Motivation, in this study operationalized as autonomous motivation.
Relatedness, in this study operationalized as interaction between parent and child, peer body size, social competences and social problems, parental feeding style and affect of the parent.
Outcome expectations, in this study operationalized as the difference between current and expected own body size.
The selection of these additional psychosocial factors to study, was made based on 1) reviews by Teixeira et al.  and Elfhag and Rössner , 2) advice by experts in the field of psychological child obesity research and treatment and 3) two prevailing psychological theories: self-determination theory  and social cognitive theory .
The self-determination theory and the social cognitive theory are general theories of human behavior, but have also been applied to weight control. According to self-determination theory, a theory of human motivation and behavior, three innate psychological needs are the basis for autonomous motivation: 1) competence (i.e. having a feeling of efficacy), 2) autonomy (i.e. perceiving an internal locus of causality; having a feeling of free will) and 3) relatedness (i.e. having a sense of security and belonging) . Conditions in the social context, like positive or negative feedback, can either enhance or hinder the fulfillment of these three basic needs . When satisfied, these psychological needs facilitate autonomous motivation, which is important for behavioral persistence in for example weight-related behaviors [55, 57].
According to social cognitive theory human behavior is a result of a continuous reciprocal interaction between behavior, cognitive and affective personal factors and environmental events [56, 58]. This interaction is influenced by people’s beliefs about their capabilities to exercise control over their own level of functioning and over events that affect their lives [56, 59]. These self-efficacy beliefs determine people’s level of motivation and the effort they are willing to put in reaching their goals [56, 59]. Self-efficacy influences outcome expectations which has an effect on the motivation to perform: when you expect to succeed that is an incentive to pursue the needed actions .
Some of the factors from the self-determination theory and the social cognitive theory are also mentioned in reviews by Teixeira et al. and Elfhag and Rössner [26, 54] on psychosocial factors that are associated with weight control in adults. These reviews for example show that more autonomous motivation is associated with weight loss maintenance [26, 54]. Other factors that are mentioned are: self-efficacy [26, 54], self-esteem , autonomy [26, 54], social support , body image  and outcome expectations [26, 54].
In sum, the objective of this study is mainly to determine whether the ability to self-regulate predicts long-term weight loss in severely obese children and adolescents and in addition to identify other psychosocial factors that may modify the relation between the general ability to self-regulate and long-term weight loss.
It is hypothesized that having less self-regulating abilities will result in less weight loss and less weight loss maintenance. The following factors are expected to negatively influence the relationship between self-regulation ability and weight loss and weight loss maintenance: less general self-efficacy, lower self-worth, less autonomous motivation, lower quality of the relationship between parent and child, larger body size of peers, less social competences, more social problems, a less adequate parental feeding style, more negative affect of the parent and unrealistic outcome expectations.