Childhood and Adolescent Obesity

What is Obesity?

Obesity has been defined as "an increase in body weight resulting from an excessive increase in body fat"(Joseph et al, 1996, p2). The problem with obesity is not weight or mass but excess adipose tissue.  Adipose tissue  is a "major energy store in the body and its size can only increase if food (energy) intake is greater than the body’s energy demands" (Caterson, 1997, p15).

Some researchers agree that Body Mass Index (BMI) is the best tool available to determine childhood obesity. BMI is the ratio of weight (kg)/ height(m)2 which gives a reasonable estimate of adiposity. A person is seen to be obese if his/her BMI exceeds the cut-off point for his/her age (Joseph et al, 1996, p2).  The World Health Organisation recommend the following guidelines for determining obesity; (Tienboon et al, 1992, p21).

Age (years)	BMI(kg/m)
<14	19-20
15	25
>16	28

Growth charts, such as weight-for-age and weight-for-height, are more frequently used to determine if children are overweight/obese rather than using BMI.  The use of BMI is usually inappropriate for infants, children and adolescents because of different rates of gain in weight and height during development.

Prevalence in Australia

In Australia approximately 50% of men and 33% of women are overweight or obese, and about 16% of adolescents are obese. It has been found that approximately 80% of obese adolescents become obese adults (Joseph et al, 1996, p2), however, the risk of obese children becoming obese adults is less clear.

It is difficult to measure overweight and obesity in children as they are continuously growing (Caterson, 1997, p12). The prevalence of obesity in Australian children is not well known with figures between 12.5% and 30% suggested (Caterson, 1997, p13). A study by Dugdale (1982) found by using a standard weight for height measurement, that 10% of Australian boys and 13% of Australian girls were classed obese. Using the same measure, an additional 22% boys and 20% of girls were classed as overweight (Dugdale, 1982, p132).

A study by Hitchcock et al (1986) investigated a selected sample of Perth primary and secondary school children. The study found children of lower social rank and those with a southern European background were over-represented among the overweight children (greater than the 90th percentile for BMI), particularly in adolescence. Children with an Asian background who were 11 years of age and younger were over-represented among the underweight children (less than or equal to the 10th percentile for BMI).

A study by Harvey et al (1993) investigated the distribution of body mass index of more than 800 randomly selected Australian school children aged 7-15 years. The distributions of BMI in Australian children were then compared to those from a representative sample from the United States. It was found that the prevalence of overweight in Australian children aged 12-14 years was lower than that in children of the same age in the United States.

Causes of Obesity

Many theories suggest causes for obesity. It does, however, appear to be a multifactorial condition which can not be easily explained.  Genetic, endocrinal and nutritional factors as well as low activity levels have  been linked with the development and onset of obesity.

Genetics

There appears to be no consensus surrounding what percentage makes up the genetic contribution towards obesity. Some studies suggest that genetic factors account for 25-40% of the aetiology of obesity (Caterson, 1997, p15). Other studies advise the genetic contribution being from 5-25% (Kimm, 1995, p1010).

Some studies have suggested that families with a low Resting Metabolic Rate (RMR) are more likely to gain weight (Caterson, 1997, p15). It has also been found that when an individual reduces their weight their RMR lowers, this is may be why many individuals find it difficult to maintain their new weight.

Some 23 genes have been linked to obesity. The specific action of each gene is not known. Some genes have a connection with the tendency to put on abnormal fat and others have been linked with the actions of lipoprotein lipase (LPL) and/or apoB100 (Caterson, 1997, p115).

An abnormal endocrine gland is often blamed for producing obesity. However this is not a common cause of obesity (Caterson, 1997, p18).

The Environment

"While genetic factors may underlie obesity, they are not sufficient. The gene pool has been stable for many generations and therefore there needs to be an environment or lifestyle change for these genetic factors to be expressed and overweight and obesity to occur. The two obvious and important factors are eating and activity"(Caterson, 1997, p17).

Eating

Food consumption quality and quantity are important factors influencing obesity. Most adult people with obesity will admit that they are excessive eaters. It is also noted that the quality of the food eaten by some obese people includes high levels of dietary fat, which are only partly used for energy and mostly used for body stores (Caterson, 1997, p17).

Not all obese individuals overeat all the time, often they eat reasonably normally and healthily but now and then binge. This is common in women in response to emotional stress, but also found in some men (Caterson, 1997, p17).

Activity

The majority of the literature available has reported that children and adolescents are more active than adults.  In spite of this, concerns have been raised as to whether they are exercising enough to confer current as well as future health benefits. 

Modern lifestyle has seen a reduction in both voluntary and incidental activities. This is an important influence on weight gain and the increase in obesity in the last decade (Caterson, 1997, p18).  

A number of studies of children and adolescents have discovered significant correlates of inactivity associated with factors such as age (younger more active), gender (males more active), ethnicity (Caucasian more active), socioeconomic status (affluent more active), school type and location, season, peer activity participation, perceived future health problems and perceived health status. What seems to be emerging, from both anecdotal and scientific reports is that children's activity levels decline throughout the teenage years. 

Some studies have found that the prevalence of obesity in children is directly related to the hours of television viewed.  Other studies, however, have failed to establish a direct correlation. Critics of television have suggested that television watching induces laziness, passivity, hyperactivity and/or many other undesirable conditions.  There are two main reason why television watching may contribute to obesity.  Firstly, it results in less activity as television watching replaces more active pursuits and secondly, television viewing  decreases the metabolic rate. (Caterson, 1997, p18) (Klesges et al, 1993, p281)(Kimm, 1995, p1010).

A study of children and television viewing in the United States by Gortmaker et al (1996), estimated that more than 60% of overweight incidences in the population can be linked to excessive television viewing time. However, a study by Robinson et al (1993) found that the hours of after school television viewing had no significant association with baseline or longitudinal change in BMI or tricep skinfold thickness.

Health Implications

Obesity in adults has been associated with an increase risk of ;

Cardiovascular disease & Hypertension
Non-insulin dependent diabetes mellitus
Gallbladder disease
Cancers of the breast, colon, endometrium and prostate.
Sleep apnoea
Increase risk of morbidity and mortality
Osteoarthritis- this is induced by the excess weight of obesity and can be a major problem. If inadequately managed it can be a barrier to adequate weight loss. The obese also have an increase of arthritis in non-weight bearing joints, for example the hands (Caterson, 1997, p21).

Serious physical complications associated with high weights in children are rare.  These do include, however, cardiomyopathy, pancreatitis, orthopaedic disorders, respiratory disorders such as upper airway obstruction and chest wall restriction.  These are largely restricted to the severely obese and are of low prevalence (Joseph et al, 1996, p2) (Caterson, 1997, p20) (Dietz, 1998, p518)

In adolescents, obesity confers significant cardiovascular risks, abnormal glucose tolerance, hypertension, and lipid profile abnormalities.

Social Implications of Obesity

The most immediate consequences of overweight during childhood and adolescence are psychosocial.

The social implications of obesity are a major problem area that is often neglected. "The obese, do less well academically, have poorer job prospects and lower self esteem. This latter often caused by repeated failures at weight loss. Children see obesity as a disability worse than losing a limb" (Caterson, 1997, p21). Obese individuals generally lead socially isolated lifestyles (Joseph et al, 1996, p2).

Obese children are often taller than their non-overweight peers, they are apt to be viewed more mature. This is an inappropriate expectation that may result in adverse effects on their socialisation (Dietz, 1998, p518).

Treatment for Obesity

The goal of managing a child with obesity is to regulate body weight while ensuring adequate nutrition for growth and development. Ideally alleviation of obesity would also cause positive physiological and psychological change (Epstein, 1998, p554).

Restricting food, in particular fat, intake is not recommended for young children as there is a risk of compromising growth. Energy dense snacks should be replaced with more nutritionally sound choices as much as possible. 

Care should be taken not to be too overzealous in restricting foods that may be considered nutritionally undesirable. Being overly restrictive in a child's food choice may be a counter productive strategy as it may lead to can increased desire for a food items to which access has been restricted (Birch, 1999, pg 1268). Children should be directed to more healthy alternatives as much as possible.

Most importantly, attention should be placed on increasing physical activity levels, which is central to tackling obesity in children.Exercise by itself does not cause major weight loss, but rather promotes changes in body composition by reducing adiposity and increasing muscle mass (Caterson, 1997, p23).

The best form of exercise is prolonged low intensity exercise, for example walking. Vigorous exercise, which is physical activity that makes an individual puff and pant, should be promoted especially for younger age groups for more immediate health benefits.

Parents play an important role in preventing and managing childhood obesity as they are important food providers and role models. They should attempt to provide healthy meals and snacks and encourage regular exercise.

The treatment of paediatric and adolescent obesity is optimistic compared to adult obesity. This may be due to the following reasons;

Support through the family
Generally, children and adolescents have not had eating and activity problems as long as obese adults.
Treatment at an early age prevents the development of excess adipose cells where adult treatment involves shrinking adipose cells. (Epstein, 1998, p554) (Caterson, 1997, p24).

Treatment of obesity using a common intervention contributes to mixed results. As stated by Epstein et al, 1998, p565 "research has identified many aetiologic  factors of obesity, including genetics, metabolic, biochemical, environmental, psychological and physiological variables. However, at an individual level it is probably rare for all of these factors to be involved in development and maintenance of obesity". Through the development of better assessment techniques interventions more appropriate to each individual can be implemented.

At present it is felt that the treatment of obesity may be most effectively achieved using a multi-component program, based on behavioural management principles (Zakus, 1982, p11).

With increasing rates of children and adolescents experiencing eating disorders, undue emphasis on specific weight targets should be avoided.  A weight loss regime may be avoided when overweight is not extreme.

Nutrition

It has been recognised that nutrition intervention is ineffective as the only treatment for paediatric obesity (Epstein, 1998, p555). The long term efficacy of weight loss programs is not good, the most important component is behaviour modification and follow up (Caterson, 1997, p20).

It has been suggested that people at risk of obesity should be offered nutrition advice in combination with increasing their activity levels (Caterson, 1997, p21).

Behaviour

When given a choice, obese children often pick sedentary activity instead of engaging in physical activity as they find physical activity less reinforcing than sedentary activity compared to their non-obese peers (Epstein, 1998, p564).

One method to increase physical activity is to reduce their access to sedentary behaviours that leads to a modification in their environment. However, Epstein et al, 1998 stated that it is important to let the child have control of activity choice. Children should be supported/ reinforced for decreasing sedentary activities and choose to replace them with physical activity (Epstein, 1998, p565).

Prevention Techniques

Joseph et al (1996) found that it is possible to improve knowledge about obesity and its prevention, either directly among teachers or indirectly among children, through the use of simple techniques such as seminars and educational activities.

Prevention is the best long term therapy for obesity.  However as Caterson, 1997, p25 stated "Many approaches have been trialed to date and they have been uniformly unsuccessful in whole population terms".

References

Barlow, S., Dietz, W. (1998) Obesity Evaluation and Treatment: Expert Committee Recommendations. American Academy of Pediatrics, 102;3. pp626.

Baur,L.(1996) Body composition and body fat in children and adolescents, Asia Pacific Journal of Clinical Nutrition, 5;2. pp100.

Caterson,I.(1997) Obesity Part of the Metabolic Syndrome, The Clinical Biochemist Reviews, 18;1. pp11-21.

Dietz,W. (1998) Health Consequences of Obesity in Youth: Childhood, Pediatrics, 101;3S. pp518-525.

Birch, O.J. (1999) Restricting access to palatable food affects children's behavioural response, food selection, and intake Am J Clin Nutr, 69, pp1264 1272.

Dugdale,A. (1982) How obese are Australian children? J Food Nutr. 39;3. pp132-133.

Epstein,L., Myers,M., Raynor,H., Saelens,B.(1998) Treatment Of Pediatric Obesity, Pediatrics, 101;3S. pp554-570.

Goran,M. (1998) Measurement Issues Related to Studies of Childhood Obesity: Assessment of Body Composition, Body Fat Distribution, Physical Activity, and Food Intake.Pediatrics, 101;3S. pp505-518.

Gortmaker,S. Must, A. Sobol, A. Peterson, K. Colditz,G. Dietz,W. (1996) Television Viewing as a Cause of Increasing Obesity Among Children in the United States 1986-1990, American Medical Association, 150;4, pp356-362.

Harvey,P., Althaus,M. (1994) The distribution of body mass index in Australian children aged 7-15 years, Aust J Nutr Diet, 51. pp151-153.

Hitchcock,N., Maller,R., Gilmour,A. (1986) Body size of young Australians aged five to 16 years, Med.J.Aust. 145. pp368-372.

Joseph,K., Ang,K., Ngo,K., Yim,G. (1997) Obesity in Children, Internet Journal of Health Promotion, URL; http://www.monash.edu.au/health/IJHP/1996/2.

Kimm,S.(1993) The role of dietary Fiber in the Development and Treatment of Childhood. Pediatrics, 96;5. pp1010-1014.

Klesges, R. Shelton, M. Klesges, L.(1993) Effects of Television on Metabolic Rate: Potential Implications for Childhood Obesity. Pediatrics, 91;2. pp281-286.

Robinson.T, Hammer. N, Killen. L, Kraemer, J. Wilson. H, Hayward. D, Taylor, C. Barr, C.(1993). Does Television Viewing Increase Obesity and Reduce Physical Activity? Cross-sectional and Longitudinal Analyses Among Adolescent Girls. Pediatrics, 91;2. pp273-280.

Rosenbaum,M. Leibel, R. (1998) The Physiology of Body Weight Regulation: Relevance to the Etiology of Obesity in Children, Pediatrics,101;3S. pp525-539.

Ross,K., Daniels,L., Douglas,H.(1980) The obese child: observations in the gymnasium of the Adelaide Children's Hospital, Med.J.Aust.2. pp80-84.

Tienboon P., Wahlqvist M., Rutishauser I. (1992) Early Life Factors Affecting Body Mass Index and Waist-Hip Ratio In Adolescence, Asia Pacific J Clinc Nutr, 1. pp21-22.

Wilcken, D., Lynch,J., Marshall, M. (1996) Aussie Kids Are Getting Fatter, Choice. 164. pp22-25.

Zakus,G. (1982) Obesity in Children and Adolescents: Understanding and Treating the Problem, Social Work in Health Care, 8;2. pp11-29.

Last Updated: March 27, 2001.