Dr. Mala Dharmalingam *
MD. DM. (AIIMS) Associate Professor and Head Unit 1 MS Ramaiah Medical College and Memorial Hospital *
The prevalence of obesity in the adolescent age group has been gradually increasing over the past decades. In a study by NHANES the prevalence of obesity had doubled in children aged 6-11 years and tripled in the age group 12-17 years. In a study done in Australia 15% of the boys and 15.8% of girls were overweight 4.5% and 5.3% of boys and girls were obese.

What are the causes of obesity?
Man has evolved so that he can store fat. Sedentary life style and consumption of energy dense food are the most important causes. Hormonal, syndromic causes although rare among children and adolescents with obesity, GH deficiency, thyroid hormone deficiency, and cortisol excess are characterized by a combination of decreased energy expenditure and decreased growth resulting in prominent central adiposity in a short, slowly growing child. Ic or molecular genetic causes account for less than 5%. The genes identified with obesity are Lepton receptor proopiomelanocortin (POMC), prohormone convertase 1, melanocortin receptors 3 and 4, and the transcription factor single - minded 1; The hormonal problems associated with obesity are, GH deficiency, thyroid hormone deficiency, and cortisol excess.

How do we evaluate obesity?
History and anthropometrics: In the initial assessment, nutrition history, assessing caloric intake, quality in terms of balance of nutrients is done. The levels of activity and any limitations because of overweight, somnolence and sleep apnea should be assessed.

Physical examination should first be directed to overall body proportions and the presence or absence of any distinctive or dysmorphic features that could guide the diagnosis to a rare obesity syndromes. Recording and graphical plotting of height, weight, BMI, and circumference should be done at each visit.

Diagnosis to rare obesity syndromes. Recording and graphical plotting of height, weight, BMI, and waist circumference should be done at each visit.

Overweight and obesity occur with excessive accumulation of body fat. Because increasing body fat is associated with increasing morbidity, the definition of overweight and obesity should be linked to health risks. Due to difficulties in direct measurement of body fat, obesity can be simply and inexpensively estimated using the BMI. BMI correlates with the amount of body fat in both children and adults. The World Health Organization (WHO) classification and U.S. dietary guidelines for obesity in adults define overweight based on health risk as a BMI of 25-30 kg/m2 or greater. However the Asia Pacific has put the cut off as 23 kg/m2. Country specific charts are important. However there is no such in India. Overweight is define in adolescents as the 85th percentile or greater of BMI for age. A recent review conducted that the evidence for use of national BMI reference data is sufficiently strong for its adoption in clinical practice and screening. An advantage of these charts is that a child can be followed up over time with graphical plotting of serial BMI measures. A disadvantage is that the charts are based on arbitrary.

Laboratory tests for body fat: BMI does not distinguish between subcutaneous and visceral fat. It is therefore useful to employ adjunctive measures of total and regional body fat.

Skinfold Thickness: This is a quick, simple, inexpensive method, and gives information on fat distribution because it is done at several body sites. It does not require a high degree of technical skill, Triceps skinfold is correlated with fat mass and, combined with BMI, increases the sensitivity for the determination of percent body fat.

Bioelectric Impedance Assay (BIA): BIA is a method of body composition assessment that is simple, quick, relatively inexpensive, and noninvasive. However, BIA measurements are highly variable because they are affected by meals; physical activity; and other variables that change the subject's hydration state, such as menstrual phase, acute illness, kidney disease, and water and electrolyte disturbances.

Hydrodensitometry: Underwater weighing requires special equipment and is used primarily for research purposes; it is not available for routine clinical care. It is useful for validation of other methods of measuring body fat.

Dual-energy x-ray absorptiometry (DEXA): This is a relatively expensive but safe method for assessing total body fat that has high precision and simplicity for the subject. X-ray exposure is minimal. DEXA also is limited by the inability to distinguish between sc and visceral fat. The method is most useful for research.

Imaging: Computed tomography and magnetic resonance imaging of the abdomen are accurate methods that can be used to measure visceral fat. However, the disadvantages are high cost radiation exposure with computed tomography.

Anthropometrics: Waist circumference or waist to hip ratios are used as indirect markers of intra-abdominal adipose tissue. As with BMI, there is some controversy as to appropriate cutoffs for adults. Waist circumference about 95 cm indicates elevated mortality rates. This parameter is also a predictor of cardiovascular and metabolic risk factors in obese children. Visceral or intra-abdominal adiposity is also associated with the metabolic syndrome in adults and children. Methodologies such as DEXA, skinfolds, and BIA do not assess visceral fat. Thus, waist circumference should be included in clinical practice as the least invasive and least invasive and least costly tool to help identify obese children at higher metabolic risk. Currently there are limited pediatric reference values for waist circumference (24, 25), and these should be developed.

Laboratory Investigations: Laboratory investigations directed at identifying comorbidities of obesity may include thyroid functions, lipid profile, complete chemistries and hepatic profile, and fasting glucose and insulin. An oral glucose tolerance test (OGTT) should be considered to exclude impaired glucose tolerance or T2DM in individuals at high risk, e.g., family history of T2DM and/or metabolic syndrome, after 10 yrs of age. Determination of serum or urinary cortisol levels should be reserved to exclude the presence of Cushing's syndrome in obese individuals who have appropriate historical information and / or physical findings.

Prevention: What is the role of life-style and diet? Studies using motion sensors have shown that children who spend less times in moderately vigorous activity are at higher risk to become obese during childhood and adolescence, as increased snacking and inappropriate food choices due to television viewing and overweight, especially in older children and adolescents. Aside from these life-style issues, eating patterns of children and adolescents have changed dramatically in the past few decades. Dietary factors that place children at risk for obesity include high fat and excess calorie intake. Obese children tend to skip breakfast but consume a large amount of food at dinner. In terms of dietary content, there is an inverse relationship between calcium intake and adiposity. The consumption of high carbohydrate soft drinks is a major contributing factor to high calorie counts, especially because these fluids tend to replace milk and calcium intake for adolescents Additionally, fast food consumption now accounts for 10% of food intake in children in U.S. Schools, Children who frequently eat fast food consume more total energy, more energy per gram of food, more total fat, more total carbohydrate, more added sugars, less fiber, less milk (calcium), and fewer fruits and vegetables than children who eat fast food infrequently. Those who are overweight are particularly vulnerable to the adverse health effects of consuming fast foods. Twenty to 40% of severely obese adults and adolescents suffer from binge eating. Binge eaters show weight symptoms of depression and anxiety with lower self-esteem when compared with nonbingeing obese individuals.

Concern of Obesity in Adolescence: Childhood obesity is now recognized as major medical and public health problem. Obesity in adults is strongly associated with many serious medical complications that impair quality of life and lead to increased morbidity. Obese children are at high risk for adult obesity, but there are as yet insufficient data to assign specific risk levels in childhood. However, obesity in childhood provides an independent contribution to the development of adult morbidity. Without proper intervention, adult morbidities will likely begin to appear in the young. There are strong epidemiologic and causal links between obesity in the young and earlier-onset T2DM.

Diabetes: Over the past decade, there has been an increase in the appearance of T2DM in children, a disease that formerly occurred almost exclusively in adults. Polycystic ovarian syndrome are also associated with insulin resistance (hypertension dyslipidemia, acanthosis nigricans, or polycystic ovarian syndrome) Fasting plasma glucose concentration after a standard OGTT is more sensitive than plasma glucose in assessing impaired glucose tolerance in youngsters, but it is also more invasive, inconvenient, and expensive. Insulin resistance is considered the greatest risk factor for the development of T2DM, A study in US showed the prevalence of metabolic syndrome at 4.2%.

Heart Disease: Obesity produces a variety of cardiac structural changes and hemodynamic alterations. Excessive adipose accumulation induces increased blood volume and cardiac output. This leads to hypertension. Sleep apnea and obesity - related hypoventilation may contribute to pulmonary arterial hypertension. In morbid obesity these abnormalities may lead to a cardiomyopathy. Studies involving obese children and cardiovascular risk are limited. The Bogalusa Heart Study indicated that increased insulin and glucose levels in heavier children and adolescents might be risk factors for increased left ventricular mass corrected for growth. Childhood obesity does predispose to endothelial dysfunction, carotid intimal medial thickening, and the development of early aortic and coronary arterial fatty streaks and fibrous plaques. Whether childhood obesity, like adult obesity, increases the risks of myocardial infarction, stroke, and certain malignancies is currently unproved.

Sleep Disorders: There is a strong association between obesity and obstructive sleep apnea (OSA) according to several cohort studies. Obese children are 4-6 times more likely to have OSA, compared with lean children.

Visceral Factors: Non-alcoholic fatty disease: Obesity is associated with a spectrum of liver abnormalities, referred to as nonalcoholic fatty liver disease. Characteristics biochemical findings include 4 to 5 fold elevations in hepatic transaminases, and 2 to 3 fold elevations in alkaline phosphatase and Gamma glutamyl transpeptidase. Bilirubin, albumin, and prothrombin may rise in later stages. The natural history varies according to histology; hepatic steatosis is frequently characterized by a benign clinical course without histological progression; however, nonalcoholic steatohepatitis may become associated with increasing fibrosis and eventual rare cirrhosis.

Orthopedic factors: Overweight children are susceptible to developing bony deformities that can predispose them to other orthopedic problems later in life. Excess weight may cause injury to the growth plate and result in slipped capital femoral epiphysis, genu valga tibia vara (Blount's disease), flat kneecap pressure/pain, flat foot, spondylolisthesis (low back pain), scoliosis, and osteoarthritis.

Dermatologic Factors: Acanthosis nigricans, frequently found in young obese individuals, is characterized by hyperpigmented, hyperkeratotic, velvety plaques on the dorsal surface of the neck, in the axillae, in body folds, and over joints. Severe skin changes correlate with elevated serum insulin levels and can be ameliorated by weight loss and consequent reduction in insulin resistance. Other skin problems commonly encountered include skin tags and keratosis pilaris.

Prevention: Public health strategies to prevent obesity should begin with schools and extend to the entire community. Schools must promote healthy eating. This should include review of vending machine offerings, food available in school cafeterias, and types of food allowed for classroom events. A curriculum for nutrition education to promote healthy eating habits, healthy body image, and weight management is essential from preschool through high school. Healthy eating opportunities include affordable, palatable fresh fruits and vegetables and lower fat food choices in school cafeterias and vending machines. Regulatory agencies should ban advertising of fast foods directed at preschool children and restrict advertising to school age children.

Lack of physical activity is not limited to inner-city populations but cuts across socioeconomic, gender, and racial lines. A first step toward increasing activity is to restrict sedentary activities. Another crucial element for children is to make exercise readily accessible at all ages in schools and residential areas. Age appropriate exercises should be fun, not punitive. Schools should mandate minimum standard for physical education, including 30-45 min of strenuous exercise two to three times weekly.

Dietary Approaches: Mild caloric restriction is safe and can be effective when obese children and their families are motivated and encouraged to change longstanding feeding behaviors. An example of such a program aimed at families with children is the traffic light diet. Significant reductions in weight are unusual and often transient unless caloric restriction is accompanied by increased energy expenditure. Diets severely restricted in calories, including high-protein, very low-caloric diets, can facilitate more dramatic short-term weight loss. However, such diets cannot be sustained under free-living conditions and are potentially dangerous. Severe caloric restriction may cause deficiencies of vitamins, minerals, and critical micronutrients; limit bone accretion and mineralization', reduce rates of linear growth; and disrupt menstrual cycles.

Exercise: A sedentary lifestyle increases the risks of childhood and adolescent obesity and predisposes to diabetes and cardiovascular disease, whereas exercise, in combination with caloric and fat restriction, reduces the rate of progression to diabetes in adults with impaired glucose tolerance and limits cardiovascular morbidity and mortality. The benefits of exercise are mediated, at least in part, by reductions in total and visceral fat stores and increases in lean body mass, which augment resting energy expenditure. Exercise enhances adipose tissue sensitivity' to insulin; reduces fasting and postprandial free fatty acid, LDL, and triglyceride concentrations; and increases plasma HDL levels. The heightened sensitivity' to insulin and induction of fatty acid oxidation enhance vascular endothelial function. Available evidence, albeit limited. Suggests that exercise can benefit obese children and reduce the risks of metabolic and cardiovascular complications.

Pharmacotherapy: If supervised lifestyle intervention fails, the patient should be referred to a subspecialist for evaluation. The extent and magnitude of comorbidities and may consider more intensive therapeutic approaches including Pharmacotherapy.

Anorectic agents: The only anorectic agent currently approved for use in obese adolescents (older than 16 yr) is sibutramine, a non-selective inhibitor of neuronal reuptake of serotonin, norepinephrine, and dopamine.

Insulin sensitizers and suppressors: The synthesis and storage of triglyceride in adipose tissue are stimulated by insulin. Thus, increases in nutrient-dependent insulin production and/or fasting hyperinsulinemia may contribute to fat storage and limit fat mobilization. By reducing fasting or postprandial insulin concentrations, certain pharmacologic agents may prove beneficial in the treatment of obese children and adults. In this drug class, only metformin treatment results in weight loss.

Bariatric Surgery: The long-term success of lifestyle intervention and pharmacotherapy in subjects with severe obesity has in general been disappointing. Marked weight loss is highly unusual and rarely sustained, and metabolic and vascular complications are common, albeit not universal. More aggressive approaches such as bariatric surgery may be indicated in selected subjects with extreme obesity and serious comorbidities. The surgical approaches now used most commonly are the gastroscopic gastric banding procedure and the Rouen-Y gastric bypass (RYGB).

Care co-ordination: How should the clinician balance lifestyle intervention, pharmacotherapy, and surgery in the treatment of obesity? Lifestyle intervention is indicated for all overweight and obese children and should be mainlined, even if more aggressive/intensive measures are adopted. Pharmacotherapy may be considered for complicated obesity in peripubertal children or adolescents who fail to respond to at least a 6-month trial of supervised lifestyle intervention despite good faith effort. The term complicated obesity implies the presence of major comorbidities including glucose intolerances, hypertension, dyslipidemia, sleep apneas or other comorbidities discussed above. Failure to respond means that the comorbidities persist or worsen despite lifestyle intervention. Good faith effort means the patient has attempted to follow dietary recommendations and has increased energy expenditure through regular exercise.

Conclusion: Obesity is a major contributing factor in increasing rates of disability among adults. The increasing prevalence of type 2 diabetes and cardiovascular problems are a cause of concern. Probably the answer lies in prevention rather in treatment. It should be aimed to mobilize all efforts to decrease weight in children in adolescents. The WHO has formulated a plan to tackle obesity, and the International Obesity task force has created a credentialing system for obesity) specialists and treatment centers. These measures along with measures from local professional bodies should help in establishing tools for weight reduction in adolescents in society.
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