Eating Disorders

The  eating  disorders  of  anorexia  nervosa  and bulimia  nervosa  are  characterized  by  severe  disturbances  in  body  image,  eating,  and  engaging in  compensatory  behaviors  that  result  in  serious medical,  psychological,  and  social  problems.  For example,  eating  disorders  increase  the  risk  of obesity,  nutritional  deficiencies,  depression  and anxiety  disorders,  chronic  pain,  osteoporosis, insomnia,  neurological  symptoms,  cardiovascular problems, substance abuse, and death. The criteria for anorexia nervosa include an intense and unrealistic  fear  of  becoming  fat,  engaging  in  behaviors intended to produce distinct weight loss, and amenorrhea resulting from the refusal to maintain a healthy weight. The body-image disturbance and consequential denial of the negative health effects of  one’s  low  weight  are  defined  as  maintaining  a weight that is less than 85% of what is considered an ideal body weight for the individual’s age, gender, and height. This denial is evident by a physiological criterion of amenorrhea that is defined as the absence of at least three consecutive menstrual cycles for women.

Two specific types of anorexia nervosa, restricting type and binge-eating–purging type, are based on  how  the  extreme  low  weight  is  reached  and maintained.  The  restricting  type  is  defined  as  the absence  of  bingeing  and  purging  behaviors.  The binge-eating–purging  type  states  that  during  the current  episode  of  anorexia  nervosa,  the  individual also engages in binges (eating inappropriately massive  amounts  of  food  in  one  set  period  of time) or purging behavior (self-induced vomiting, misuse  of  laxatives,  diuretics,  or  enemas).  While anorexia  nervosa  can  affect  men  and  women  of any  age,  race,  and  socioeconomic  and  cultural background,  the  occurrence  of  anorexia  nervosa is  10  times  higher  in  the  female  population  than among males.

The  criteria  for  bulimia  nervosa  are  similar  to that of anorexia in that they also outline an intense fear of becoming fat, but they differ by including the requirements of powerful urges to overeat and subsequent binges that are followed by engaging in some sort of compensatory behavior in an attempt to avoid the weight gain effects of excessive caloric intake. The fear experienced by an individual with bulimia  nervosa  is  also  in  regard  to  body-image disturbance.  The  paradox  is  the  presence  of  the uncontrollable urges to overeat, resulting in binges. These  binges  are  defined  as  occurring  within 2 hours and eating an amount of food that is larger than most people would consume in a similar time and setting coupled with a sense of lack of control (inability to stop eating) during the binge. Both the body-image disturbance and binges result in engaging  in  compensatory  behaviors  to  evade  weight gain.  Compensatory  behaviors  are  separated  into purging and nonpurging types. Purging behaviors include  self-induced  vomiting,  use  of  laxatives, diuretics,  enemas,  or  medication  abuse.  In  comparison,  nonpurging  behaviors  include  fasting  or excessive exercising. A qualification for a diagnosis of bulimia nervosa is that the binge eating and inappropriate compensatory behaviors must occur, an average, at least twice a week for 3 months. In contrast  to  those  with  anorexia  nervosa,  people with  bulimia  nervosa  are  able  to  maintain  body weight at or above a minimal normal level.

Bulimia  nervosa  is  considered  to  be  less  life threatening  than  anorexia  nervosa;  however,  the incidence of bulimia nervosa is higher. Bulimia nervosa is nine times more likely to occur in women than men. The vast majority of those with bulimia nervosa  are  at  normal  weight.  Antidepressants are  widely  used  in  the  treatment  of  bulimia  nervosa. Patients who have bulimia nervosa are often linked  with  having  impulsive  behaviors  involving overspending  and  sexual  activity,  as  well  as  having family histories of alcohol and substance abuse and mood and eating disorders.

Eating  disorders  exist  and  develop  on  a  continuum  with  health  detriment  occurring  throughout   the   entire   span   of   the   development   and maintenance  of  the  disorder.  That  is,  cognitions and  behaviors  seen  in  full-blown  disorders  begin with  less  frequency  or  intensity  and  subsequently increase as the disorder develops. While the antecedents and causes of eating disorders are myriad and complex, excessive exercise has been the focus of much research and clinical attention. Although study  design  and  quality  have  varied  greatly, researchers  typically  find  that  a  large  percentage of  individuals  with  eating  disorders  engage  in excessive  exercise.  Thus,  this  entry  will  primarily focus  on  the  relationship  between  excessive  exercise  behavior  (exercise  dependence)  and  eating disorders. Note that the entry on the female athlete triad focuses on eating disorders and athletes.

Of  importance,  according  to  the  Diagnostic and  Statistical  Manual  of  Mental  Disorders,  4th Edition,  Text  Revision  (DSM-IV-TR),  exercise becomes excessive when “it significantly interferes with important activities, when it occurs at inappropriate  times  or  in  inappropriate  settings,  or when  the  individual  continues  to  exercise  despite injury or other medical complications” (American Psychiatric   Association,   2000,   pp.   590–591). This  definition,  however,  fails  to  quantify  the amount  needed  to  determine  if  exercise  is  excessive.  Because  excessive  exercise  and  its  negative health  outcomes  have  been  studied  far  less  than the  other  diagnostic  symptoms,  more  research  is needed to better understand excessive exercise and eating  disorders.  In  an  attempt  to  provide  clarity to  the  excessive  exercise  construct,  researchers advocate for either revising the diagnostic criteria with  regard  to  excessive  exercise,  or  eliminating excessive exercise as a diagnostic criterion because of lack of empirical support for it. In short, considerable  debate  exists  regarding  eating  disorder classification  in  general,  and  in  particular  with excessive exercise, regarding how best to define it, or even whether to include excessive exercise as a compensatory behavior for bulimia nervosa.

Relationship Between Excessive  Exercise and Eating Disorders

Current  exercise  guidelines  identify  the  minimum amount  of  exercise  needed  to  experience  health benefits.  The  guidelines  also  recommend  that  an increased  amount  of  exercise  is  associated  with additional  benefits.  Although  increases  above  the minimum guidelines are encouraged, no consensus exists on how much is too much, that is, at what point any further increase in exercise may have a negative effect on one’s health.

By  definition,  a  regimen  of  exercise  that  has become detrimental to an individual’s physical and psychological health constitutes excessive exercise or  exercise  dependence.  Simply  stated,  exercise dependence  is  a  craving  for  leisure-time  physical activity, resulting in uncontrollably excessive exercise behavior that manifests itself in physiological (e.g., tolerance) or psychological (e.g., withdrawal) symptoms. Characteristics of exercise dependence include  exercising  despite  either  injury  or  illness; experiencing withdrawal effects when an exercise session  is  missed;  and  giving  up  social,  occupational, and family obligations to exercise. Exercise dependence may also play a pivotal role in explaining the function of exercise behavior in the development and maintenance of eating disorders.

The  relationship  between  exercise  and  eating pathology, however, is complex and controversial. Diagnostic  criteria,  correlational  research,  and clinical  observation  show  a  higher  prevalence  of exercise  in  individuals  with  bulimia  nervosa  and anorexia  nervosa  than  in  non-eating-disordered samples. This is in part because of exercise’s ability to  offset  caloric  intake,  resulting  in  weight  loss. For  many  individuals  beginning  to  experience  an eating disorder, diet and compensatory behaviors, such  as  picky  eating,  skipping  meals,  and  fasting, may only reduce the number of calories consumed.  Consequently,  weight  loss  is  slowed  and the  individual  may  seek  complementary  methods to  accelerate  weight  loss.  If  progress  with  weight loss seems slow, compulsive exercise may be added in  an  attempt  to  increase  weight  loss.  While  this seems reasonable and sufficient to explain the role of  exercise  in  eating  disorders,  simply  examining the  amount  of  exercise  does  not  explain  either why  or  to  whom  excessive  exercise  may  become problematic.  Thus,  more  recent  investigations reveal  that  psychological  factors  such  as  exercise dependence may better explain the role of exercise in  eating  disorders.  Therefore,  a  closer  examination of prevalence rates and psychological factors indicates  a  much  more  complicated  relationship between exercise and eating disorders.

The  belief  that  exercise  is  associated  with  the development and maintenance of eating disorders is  based  largely  on  cross-sectional,  retrospective, and  case  study  designs  that  fail  to  adequately assess and quantify excessive exercise. For example,  there  is  a  long  standing  clinical  observation that  most  hospitalized  inpatients  receiving  treatment  for  anorexia  nervosa  engage  in  excessive amounts  of  exercise  during  the  development  or maintenance  of  their  eating  disorder.  However, no  definition  is  provided  for  what  is  considered excessive  exercise.  Similarly,  recent  studies  have correlated  participation  in  athletics  (populations that engage in large amounts of physical activity) with  deleterious  eating  attitudes  related  to  eating disorders. Thus, researchers have focused on exercise amount contributing to the development and maintenance of eating disorders. However, focusing on exercise amount may be misleading because much  of  the  research  examining  excessive  exercise has relied on biased sampling methods using unvalidated self-report exercise measures that lack a  clear,  concise,  and  consistent  definition  of  how much exercise is excessive. Furthermore, many of the operational definitions used for excessive exercise fail to meet the minimum amount of exercise needed  to  achieve  the  health-related  benefits  of physical activity.

Primary Versus Secondary Dependence and Eating Disorders

Most  of  the  research  examining  the  relationship between  excessive  exercise  and  eating  disorders has focused on the amount of exercise contributing to the development of eating disorders but has overlooked psychological variables that may mediate such a relationship. Understanding the psychological antecedents of exercise may help clarify the relationship  between  eating  disorders  and  excessive  exercise  by  offering  insight  into  the  distinction  between  primary  versus  secondary  exercise dependence.  Primary  exercise  dependence  occurs when  the  individual  meets  criteria  for  exercise dependence  and  continually  exercises  solely  for the  psychological  gratification  resulting  from  the exercise  behavior.  Secondary  exercise  dependence occurs when an exercise dependent individual uses increased amounts of exercise to accomplish some other  end,  such  as  weight  management  or  body composition manipulation.

Simply  stated,  it  is  important  to  distinguish whether the individual is exercising excessively to satisfy the need to exercise (primary dependence) or if they are engaging in increased amounts of exercise as a compensatory behavior that is secondary to other pathology, such as an eating disorder (secondary dependence). Because exercise can be used as a compensatory behavior to prevent or reverse weight gain, secondary exercise dependence in the context of eating disorders occurs when individuals  meet  the  criteria  for  exercise  dependence  and continually  exercises  to  manipulate  and  control their own body; thus, exercise dependence is secondary to an eating disorder. Recently, researchers have  found  that  exercise  dependence  symptoms, not  exercise  behavior,  mediate  the  relationship between exercise and eating pathology. Thus, psychological factors, not the amount of exercise, may better explain why the exercise dependence–eating disorder relationship exists.

The Exercise and Eating Disorders Model

The  limitations  of  biased  clinical  observations, retrospective  research  designs,  vague  operational definitions of excessive exercise, inconclusive animal  research,  and  overlooking  potential  mediating  psychological  variables  support  the  need  for theoretically  driven  models  that  explain  the  relationship between eating disorders and the psychological motivation as well as the physical effects of exercise.

Previous models have been advanced that postulate  how  and  why  obligatory  attitudes  toward exercise   may   influence   the   development   and maintenance  of  eating  pathology  and  disorders. However,  these  models  offer  limited  insight  into why  the  benefits  typically  experienced  as  a  result of  regular  exercise  do  not  occur  in  eating  disorders.  For  example,  exercise  may  impart  positive improvements  on  the  eating  disorder  risk  factors of anxiety, body image, depression, stress reactivity, and self-esteem in non-eating-disordered populations. Similarly, cardiovascular benefits, such as increased  cardiac  mass,  increased  stroke  volume and  cardiac  output  at  rest  and  during  exercise, lower resting heart rate and blood pressure, and a decreased tendency for blood clotting are pertinent to  eating  disorder  research  because  cardiac  damage  can  occur  early  during  eating  disorder  development.  Exercise  also  has  the  ability  to  reduce adiposity,  thus  contributing  to  a  leaner,  more  fit, and  culturally  ideal  body  type.  Moreover,  sociocultural pressures to be thin and social comparison are risk factors for the development of eating disorders. Furthermore, the metabolic benefits of exercise  include  decreased  triglycerides  and  increased high-density  cholesterol,  increased  insulin  mediated  glucose  uptake,  and  a  possible  increase  in resting  metabolism.  Finally,  exercise  increases skeletal  muscle  mass  and  bone  density  in  youth and  it  is  related  to  the  retention  of  bone  mineral density  in  older  adults.  This  has  implications  in the development of osteoporosis, a common consequence  of  prolonged  eating  disorder  behaviors. Thus, exercise is an effective intervention for many physical  and  psychological  health  issues,  and  yet recent recommendations for research to reexamine the  role  of  exercise  in  eating  disorders  have  been largely overlooked.

Heather  Hausenblas,  Brian  Cook,  and  Nickles Chittester presented a conceptual model examining such  aforementioned  relationships  (see  Figure  1). Their Exercise and Eating Disorders Model states that  regular  exercise  is  associated  with  improvements  in  several  physical  (cardiovascular,  metabolic benefits, decreased adiposity, and increases in bone density), psychological (body image, depression, anxiety, stress reactivity, and self-esteem), and social  benefits  that  are  also  risk  factors,  maintenance factors, outcomes, or diagnostic criteria for eating  disorders.  Hence,  this  exercise  and  eating disorders  model  has  consolidated  and  supported several  narrative  and  meta-analytic  reviews  that have  shown  exercise’s  ability  to  impart  positive improvements  on  eating  disorder  risk,  development,  and  maintenance  factors.  The  model  also extends our current understanding of the relationship  of  exercise  and  health  status  by  including exercise dependence. That is, exercise dependence may  explain  why  the  development  of  eating  disorders  may  supersede  the  expected  benefits  of exercise.  Simply  stated,  this  model  posits  that  in the  absence  of  pathological  psychological  factors such as exercise dependence, the benefits conveyed by regular exercise—improvements in depression, anxiety,  stress  reactivity,  self-esteem,  and  body composition—may counteract the risk factors for eating  disorders  like  body  dissatisfaction,  depression, anxiety, and increased body mass.

Recent   research   by   Cook   and   colleagues, Hausenblas, Daniel Tuccitto, and Peter Giacobbi, has  provided  initial  support  for  this  exercise  and eating  disorder  model,  revealing  that  the  psychological  health  benefits,  conveyed  by  exercise  can reduce the risk of eating disorders.

First,  university  students  completed  self-report measures of physical and psychological quality of life,  exercise  behavior,  eating  disorder  risk,  and exercise  dependence  symptoms.  Structural  equation  modeling  analysis  found  support  for  the mediation  effect  of  exercise  dependence  on  eating disorders as well as the effect of psychological well-being  on  eating  disorders.  Together,  exercise behavior,  psychological  well-being,  and  exercise dependence  symptoms  predicted  22.9%  of  the variation  in  eating  disorders.  Thus,  these  results indicated  that  the  psychological  health  benefits conveyed  by  exercise  reduced  eating  disorders. These  results  were  replicated  in  a  more  diverse sample  of  college  students  in  another  study  by Cook and various colleagues in 2011.

Exercise Interventions and Eating Disorders

The   initial   tests   of   the   Exercise   and   Eating Disorders  Model  suggest  that  the  model  may synthesize  two  divergent  lines  of  research.  That is,  exercise  may  play  a  role  in  the  development of  eating  disorders  when  exercise  dependence  is simultaneously  present.  Similarly,  the  psychological health benefits of exercise may also reduce eating  disorder  risk  for  individuals  without  exercise dependence.


Preliminary research has found that mild to moderate exercise appears to attenuate eating disorder symptoms  in  patients  suffering  with  anorexia  or bulimia  nervosa.  However,  before  exercise  interventions  are  considered  mainstream,  future  randomized controlled trials are needed to establish a dose–response  relationship  for  exercise  and  identify the conditions (e.g., type or severity of eating disorder, minimum weight level, and exercise environment)  under  which  an  exercise  intervention may  be  undertaken.  Interest  in  exercise  dependence  and  eating  disorders  is  recent  but  provides a context as to why the relationship between exercise  and  other  pathologies,  such  as  body-image disturbance and eating disorders, exists.


Figure 1    The Exercise and Eating Disorder Model



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