Obesity and Sports

Obesity is commonly defined as a body mass index of 30 kg/m2or higher. Increasing rates of obesity in  many  countries  represent  a  great  challenge  for public  health.  In  the  United  States,  for  example, the rate of adult obesity exceeds 35%. Obesity is associated  with  increased  risk  of  premature  mortality  resulting  from  chronic  diseases  (e.g.,  diabetes,  cardiovascular  and  cerebrovascular  disease, certain  cancers),  increased  disability  (e.g.,  knee osteoarthritis,  chronic  back  pain,  fatigue),  and increased health care costs.

The  etiology  of  obesity  is  multifactorial,  comprising both genetic and epigenetic factors. While an increasing number of putative risk factors continually emerge (including such novel contributors as  sleep  deprivation  and  stress),  the  “big  two” causal factors are diet and physical inactivity.

Obesity is of special interest to exercise professionals  because  obese  individuals  exhibit  lower rates  of  physical  activity  (PA)  participation  and higher  rates  of  nonadherence  and  drop-out  than their  normal-weight  counterparts.  However,  the reasons  behind  this  phenomenon  remain  unexplored,  severely  limiting  the  intervention  options that are available to practitioners.

The Challenge

While  most  scientific  organizations  and  public health agencies currently recommend a minimum of 30 minutes of moderate-intensity PA on 5 days per week for health maintenance in the general population, the recommended dose for weight management is more demanding. Specifically, most organizations recommend at least 60 minutes of activity per day to prevent weight gain and at least 60 to 90 minutes per day for the avoidance of weight regain in individuals who were previously overweight or obese.

Nearly  all  obese  individuals  report  that  they would  like  to  weigh  less  (90%  of  men,  96%  of women).  Approximately  two  thirds  report  doing something in an effort to lose weight. Even of those obese  individuals  who  say  that  they  are  doing something to lose weight, however, the percentage of them who report engaging in PA (approximately 61% of men, 56% of women) is lower than that in the general population.

The  magnitude  of  the  problem  becomes  more clearly evident when one examines how much PA obese individuals do. The percentage of those who do not meet the minimum recommended amount of PA for health approaches 80%. In 2000, according to Behavioral Risk Factor Surveillance System data,  21.3%  of  obese  men  and  15.9%  of  obese women  trying  to  lose  weight  reported  combining eating fewer calories with at least 150 minutes of PA per week. Only 6% of men and 3% of women reported  combining  eating  fewer  calories  with  at least 420 minutes of PA per week (i.e., 60 minutes per  day  on  average).  When  activity  is  measured objectively  via  accelerometers,  the  percentage  is even  lower.  In  a  2009  study  of  1,297  obese  participants, which was conducted by Deborah Rohm Young  and  collaborators,  only  1.7%  were  found to  be  active  at  least  at  a  moderate  intensity  for at least 60 minutes per day. On average, the participants  in  this  sample  did  only  12.8  minutes  of moderate and 2.0 minutes of vigorous PA per day.

Reverse Causation

When considering the relationship between physical  inactivity  and  obesity,  most  researchers  and practitioners  assume  that  causation  is  unidirectional: People who do less activity become obese. However,  longitudinal  studies  from  several  countries  have  shown  that,  whereas  the  inactivity– obesity  link  is  usually  weak  or  nonexistent,  the obesity–inactivity link is always robust.

This  finding  has  several  implications.  First,  it underscores the importance of efforts to address the growing  problem  of  childhood  obesity  because  it suggests that, once obesity develops, it becomes an important barrier to PA participation. Second, this finding  shows  that  obese  individuals  face  unique challenges  in  their  efforts  to  become  and  remain physically  active,  beyond  those  faced  by  their normal-weight and even overweight counterparts.

Psychosocial Impact

Extensive  evidence  indicates  that  obesity  is  associated  with  significant  declines  in  quality  of  life (QOL)  and  a  range  of  mental  health  problems. Among obese youth, self-reported QOL has been found  to  be  comparable  to  that  of  children  and adolescents  diagnosed  with  cancer.  Shame  and social  isolation  are  presumed  to  be  significant mediators for this effect. Among adults, epidemiological data indicate that obesity is associated with a 25% increase in the risk for mood and anxiety disorders. Longitudinal studies, such as the British Whitehall  II  study,  have  also  shown  that,  while obesity predicts mental health problems, the case is at least as strong for the reverse order: Individuals with  a  higher  number  of  mental  health  problems have a higher risk of becoming obese over time.

Possible Reasons for Physical Activity Avoidance

The reasons for the extremely low rates of PA participation  among  obese  individuals  are  not  fully understood.  Based  on  preliminary  evidence,  the hypotheses that have emerged include the following.  First,  possibly  due  to  media  messages,  many obese  individuals  begin  activity  regimens  with unrealistically high weight loss expectations. When these expectations are violated, frustration ensues.

Second, a high number of obese individuals experience  self-presentational  concerns  in  the  context of  PA,  resulting  in  social  physique  anxiety  (SPA). Under  the  influence  of  this  anxiety,  several  environmental cues, such as the presence of others or wall-to-wall  mirrors,  are  interpreted  as  threatening.  Third,  perhaps  as  a  result  of  prior  negative experiences, a high percentage of obese individuals report  negative  or  dysfunctional  attitudes  toward PA. Approximately 25% report feeling “too fat to exercise.” In turn, this perceived barrier is associated with feeling too shy or embarrassed and having a poor exercise identity. Fourth, several studies have found evidence of both explicit and implicit antifat  bias  among  exercise,  nutrition,  and  medical  professionals,  as  well  as  obesity  specialists. For  example,  exercise  science  students,  on  average,  endorse  statements  such  as  “Fat  people  are physically  unattractive”  and  “There  is  no  excuse for being fat.” Fifth, a growing number of studies show that physiological and biomechanical problems associated with obesity contribute to making the  exercise  experience  less  pleasant.  It  has  been found, for instance, that obese individuals experience more pain (possibly due to heavier impacts on knees and lower back), higher perceived exertion, more  dyspnea,  and  more  uncomfortable  thermal sensations during exercise.

References:

  1. Ball, K., Crawford, D., & Owen, N. (2000). Too fat to exercise? Obesity as a barrier to physical activity. Australian and New Zealand Journal of Public Health, 24(3), 331–333.
  2. Chambliss, H. O., Finley, C. E., & Blair, S. N. (2004). Attitudes toward obese individuals among exercise science students. Medicine and Science in Sports and Exercise, 36(3), 468–474.
  3. Ekkekakis, P., Lind, E., & Vazou, S. (2010). Affective responses to increasing levels of exercise intensity in normal-weight, overweight, and obese middle-aged women. Obesity, 18(1), 79–85.
  4. Kivimäki, M., Lawlor, D. A., Singh-Manoux, A., Batty, G. D., Ferrie, J. E., Shipley, M. J., et al. (2009). Common mental disorder and obesity: Insight from four repeat measures over 19 years: Prospective Whitehall II cohort study. British Medical Journal, 339,
  5. Young, D. R., Jerome, G. J., Chen, C., Laferriere, D., & Vollmer, W. M. (2009). Patterns of physical activity among overweight and obese adults. Preventing Chronic Disease, 6(3), A90.

See also: