Childhood obesity
Synonyms and keywords: obesity in kids, obesity in children, pediatric obesity

# Overview
Childhood obesity is a Body Mass Index (BMI) at or above the 95th percentile for children of the same gender and age. It is a serious health problem that can result in health complications. Childhood obesity can be caused by dietary factors, lifestyle factors, underlying medical conditions, genetic causes or certain medications.  Obesity may present with high blood pressure, shortness of breath, sleep apnea, gastroesophageal reflux, constipation, insulin resistance, constipation, or irregular menstruation. The presence of polyuria and polydipsia suggests possible diabetes, excess facial hair, insulin resistance and irregular menstruation in adolescent girls may be due to polycystic ovary syndrome (PCOS) and dry skin, constipation and intolerance to cold suggest hypothyroidism. laboratory tests indicated depend on the clinical presentation. Management of obesity includes the treatment of any underlying medical conditions and lifestyle modification.

# Historical Perspective
- Obesity was first recognized as a medical disorder by Hippocrates, an ancient Greek physician, in  
- In circa 11th century, the complications of obesity including narrowed blood vessels, stroke, and difficulty breathing were described by Avicenna in his book Cannon of Medicine.

# Classification
- Childhood obesity may be classified according to age- and gender- adjusted BMI into two groups:
- Obesity: BMI is 95th percentile
- Severe obesity: BMI 120% of the 95th percentile or BMI 35 kg/m2.

# Pathophysiology
- The pathogenesis of childhood obesity is characterized by fat accumulation due to an energy imbalance.
- This energy imbalance is the result of excess calories intake and/ or decreased calories expenditure.
- It has been suggested that a dysfunction in the ghrelin/leptin hormonal pathway may contribute to abnormal appetite control and energy balance.
- Gene mutations in single genes including Leptin (LEP), Leptin Receptor (LEPR), Pro-opio melanocortin (POMC) has been associated with the development of some cases of childhood obesity. 

# Causes
Childhood obesity may be caused by unhealthy dietary intake, unhealthy lifestyle , environmental factors, psychological stress , genetic causes , medication-induced  or cerebral injury.

## Dietary factors
Children and adolescents are consuming low nutrient high-calorie foods and beverages at home, school and other places. They are consuming more fast food which is low in nutrients and high in calories, fat and sodium. CDC reports that children and adolescents in the U.S. consumed an average of 13.8% of their daily calories from fast food during 2015-2018. In addition, they are consuming large amounts of sugar-sweetened beverages which has been directly associated with obesity in multiple reviews. 

## Lifestyle factors
Physical inactivity, excess use of screen time and inadequate sleep also contribute to the obesity epidemic. 

## Environmental factors
Eating habits of the child are affected by demographics, lunch policies at schools and work demands on parents.

## Psychological stress
Chronic stress increases the risk of obesity, diabetes, heart disease, metabolic syndrome and mental health problems.

## Endocrine causes
There are hormonal disorders that may be associated with weight gain and obesity in children including: hypothyroidism, cushing's syndrome, polycystic ovary syndrome (PCOS), precocious puberty, and pseudohypoparthyroidism.

## Genetic causes
Often, a child whose parents are overweight or obese will also be overweight or obese. Although this is often caused by shared unhealthy eating habits in the household, several genetic causes have been identified as a cause of obesity. These can be divides into monogenic causes, syndromic obesity and polygenic obesity. Monogenic obesity is caused of a mutation to a single gene including Leptin (LEP) mutations, Leptin Receptor (LEPR) mutations, Pro-opio melanocortin (POMC) mutations, MC4R deficiency, Proconvertase (PC1/2) deficiency, SIM1 deficiency, NTRK2/BDNF mutations and SH2B1 mutations. Syndromic obesity include Prader Willi Syndrome (PWS), Cohen syndrome, Turner syndrome, down syndrome, and Laurence-Moon-Bardet-Biedl syndrome.

## Medication-induced
Medications that may cause weight gain in children include second-generation antipsychotics, glucocorticoids, risperidone, clozapine, and tricyclic antidepressants.

## Cerebral injury
Obesity can occur after acquired hypothalamic lesions following surgery, meningitis or ischemic injury.

# Differentiating childhood obesity due to lifestyle factors from other Diseases
- Childhood obesity due to lifestyle factors must be differentiated from other diseases that cause obesity, high blood pressure, and insulin resistance such as:
- Hypothyroidism
- Cushing's syndrome
- Polycystic ovary syndrome (PCOS)

# Epidemiology and demographics
- The prevalence of children who are overweight or obese worldwide is approximately 38 million in children under the age of 5 in 2019 and more than 340 million between 5 and 19 years old in 2016.
- In 2015-2016, the prevalence of Childhood Obesity in USA was estimated to be 13.9% among children aged 2 to 5 years, 18.4% among children aged 6 to 11 and 20.6% among adolescents aged 12 to 19 years.

## Age
- Children of all age groups may develop Childhood Obesity.
- Childhood Obesity is more commonly observed among children aged 12 to 19 years old in the USA. This is followed by children aged 6 to 11 years old and then children aged 2 to 5 years of age.

## Gender
- Childhood Obesity prevalence by gender is different depending on the region.
- Males are more commonly affected than females 5 to 19 years of age in most high and upper middle-income countries.

## Race
- There are racial differences for obesity in children.
- Obesity prevalence was higher among Hispanics and non-Hispanic blacks than non-Hispanic whites and non-Hispanic Asians.

# Risk Factors
- Common risk factors in the development of Childhood obesity are high calorie diet, lack of physical activity, children who have obese family members, stress and low-income households.

# Natural History, Complications and Prognosis
- If left untreated, patients with childhood obesity may progress to develop glucose intolerance, type 2 diabetes, high blood pressure, high cholesterol, asthma, obstructive sleep apnea, non-alcoholic fatty liver, gall stones,joint pain and depression.
- Common complications of childhood obesity include the progression to adult obesity and increased risk of heart disease, diabetes and cancer risk.
- Obese children often suffer from weight stigma, teasing and bullying amongst their peers. They experience descrimination in the society. They are more likely to suffer from low self esteem, anxiety and depression.

# Diagnosis

## Diagnostic Criteria
- The diagnosis of childhood obesity for children age 2 and older is made when the Body Mass Index (BMI) is at or above the 95th percentile on the BMI-for-age growth chart.

## History and Symptoms
- Symptoms of childhood obesity may include the following:
- Shortness of breath
- Sleep apnea
- Constipation
- Gastroesophageal reflux
- Irregular menstruation

## Physical Examination
- Physical examination may be remarkable for:
- Stretch marks on hips and abdomen
- Acanthosis nigricans
- Dry skin, constipation, and fatigability may be signs of hypothyroidism.
- Accumulation of fat in the neck and trunk, moon facies, facial plethora, acanthosis nigricans, acne, and hirsutism may suggest cushing syndrome.
- Signs of early sexual development may be a sign of precocious puberty.
- Acne, hirsutism, and acanthosis nigricans in an adolescent girl may suggest polycystic ovary syndrome.

## Laboratory Findins
- Overweight and obese Children require screening tests:hemoglobin A1C, fasting plasma glucose, 2-hour plasma glucose, and fasting lipids.
- The following tests may be indicated for children with obesity depending on the clinical presentation:
- TSH, T4, T3, and free T4
- Adrenal function tests
- Liver function tests
- Serum leptin
- Serum calcium, phosphorus and parathyroid hormone
- Gonadotropin-releasing hormone agonist stimulation test 
- Free testosterone, total Testosterone, LH, FSH, and dehydroepiandrosterone sulfate.

# Treatment

## Medical therapy
- Management of obesity in children focuses on safely reducing the BMI of the child, preventing and managing complications.
- The mainstay of therapy for obesity in children is lifestyle modification through diet, exercise and behavioral modification.
- Setmelanotide, a melanocortin-4-receptor agonist was approved by the U.S. Food and Drug Administration (FDA) for children age 6 and older with obesity caused by three rare genetic disorders.

## Surgery
- Bariatric surgery are performed in some adolescents with severe obesity.

## Prevention
- There are multiple preventive measures available for childhood obesity
- Effective measures for the primary prevention of childhood obesity include exclusive breast feeding for the first 6 months of life, consumption of fruits and vegetables, drinking water, restriction of sweetened drinks and sugary snacks, regular physical activity, limiting screen time, reducing stress, and providing a healthy sleep routine.