Childhood obesity can be categorized into simple obesity and pathological obesity. Simple obesity is generally considered a result of energy imbalance, where energy intake exceeds energy expenditure, leading to excessive fat accumulation in the body. It is often influenced by multiple genes interacting with environmental factors such as dietary habits and physical activity. Most cases of childhood obesity are classified as simple obesity. Currently, obesity is a global epidemic, posing threats to children’s health and often continuing into adulthood, increasing the risk of diseases such as diabetes and cardiovascular conditions. Therefore, obesity is a major concern for pediatric healthcare professionals, requiring immediate solutions.
Etiology
Excessive Energy Intake
Excessive energy consumption is the primary cause of obesity. High-energy foods and sugary drinks contribute additional energy intake, making them significant contributors to childhood obesity. Family environment and parental behavior also play a key role; poor dietary habits and lifestyle choices by parents directly influence their children’s behavior. Additionally, maternal overnutrition during pregnancy has been linked to increased risk of obesity during childhood and later in life.
Insufficient Physical Activity
Sedentary behaviors such as playing computer or video games, avoiding recess activities, or prolonged television viewing, combined with insufficient physical exercise, are important factors contributing to obesity. Even minimal food intake can lead to obesity under these conditions. Many obese children tend to dislike exercise, creating a vicious cycle.
Genetic Factors
Compared to environmental factors, genetic predisposition plays a larger role in obesity development. Current research suggests that human obesity involves over 600 genes, markers, and chromosomal regions. Familial obesity exhibits a polygenic inheritance pattern. The likelihood of children becoming obese reaches 70%-80% when both parents are obese, approximately 40%-50% when one parent is obese, and only 10%-14% when neither parent is obese.
Other Factors
Eating too quickly, imbalance in satiety and hunger regulation leading to overeating, psychological stressors (e.g., the loss of a loved one or poor academic performance), and mental health abnormalities may also contribute to excessive food consumption in children.
Pathophysiology
Thermoregulation and Energy Metabolism
Obese children demonstrate reduced sensitivity to changes in external temperature. Energy expenditure for heat production is lower compared to non-obese children, leading to a tendency for lower body temperature in obese individuals.
Lipid Metabolism
Obese children often exhibit elevated levels of plasma triglycerides, cholesterol, very low-density lipoprotein (VLDL), and free fatty acids, combined with reduced high-density lipoprotein (HDL). These abnormalities increase risks of future conditions such as arteriosclerosis, coronary heart disease, hypertension, and gallstone disease.
Protein Metabolism
Abnormal purine metabolism is common among obese individuals, with elevated blood uric acid levels, increasing the likelihood of gout.
Endocrine Changes
Endocrine changes are frequently observed in obese children.
Thyroid Function
Levels of total T4, free T4, total T3, free T3, reverse T3, protein-bound iodine, and iodine-131 uptake are typically normal. The hypothalamus-pituitary-thyroid axis also remains unaffected, but reduced T3 receptor levels are believed to contribute to decreased heat production.
Parathyroid Hormone (PTH) and Vitamin D Metabolism
Serum PTH levels are elevated in obese children, with increased levels of 25-(OH)D3 and 1,25-(OH)2D3. These changes may be linked to bone-related complications in obese individuals.
Growth Hormone Levels
Plasma growth hormone levels are reduced in obese children, with a disappearance of peak secretion during sleep and a delayed response to hypoglycemia or arginine stimulation. However, insulin-like growth factor-1 secretion remains normal, and increased insulin levels provide compensatory action for reduced growth hormone, preventing significant growth and development abnormalities.
Sex Hormones
Female individuals with obesity often show elevated estrogen levels, which may result in menstrual irregularities and infertility. In male individuals, aromatization of androgens into estrogens within adipose tissue leads to higher estrogen levels, causing mild sexual dysfunction or impotence, although testicular development and sperm formation remain unaffected.
Glucocorticoids
Urinary levels of 17-hydroxy steroids, 17-ketosteroids, and cortisol tend to be elevated in obese individuals, while plasma cortisol is either normal or slightly increased, with a preserved diurnal rhythm.
Insulin and Glucose Metabolism
Obese individuals often exhibit hyperinsulinemia alongside insulin resistance. These changes result in abnormal glucose metabolism, potentially leading to impaired glucose tolerance or diabetes.
Clinical Manifestations
Obesity can occur at any age but is most common during infancy, ages 5-6, and adolescence, with boys being affected more frequently than girls. Affected children often exhibit a strong appetite and a preference for sugary and high-fat foods. Children with marked obesity may experience fatigue, shortness of breath following physical activity, or leg pain. Severe obesity can result in obesity hypoventilation syndrome, where excessive fat accumulation restricts chest and diaphragmatic movements, leading to inadequate pulmonary ventilation, shallow and rapid breathing, respiratory failure, or even sudden death.
Obese girls may experience earlier sexual maturation, while in boys, puberty may be delayed. Psychologically, obese children often face challenges, such as avoiding interactions with peers due to fear of ridicule, which may lead to self-esteem issues, shyness, and feelings of loneliness.
Physical examination often reveals abundant subcutaneous fat with even distribution. The abdomen may appear distended and sagging. In severe cases, excessive subcutaneous fat may cause skin folds on the chest, abdomen, hips, and thighs. Due to excessive weight, walking can place a heavy load on the lower limbs, potentially resulting in genu valgum (knock-knees) and flat feet. In girls, fat deposits in the chest area must be differentiated from breast development, where breast tissue nodules can be palpated. In males, fat in the inner thighs and perineum may obscure the penis within the fat pad of the pubic region, potentially being misdiagnosed as underdeveloped genitalia. Some children may also present with hypertension.
Laboratory Examinations
Routine laboratory assessments for obese children often include testing glucose tolerance, blood glucose levels, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides, and cholesterol. Abnormalities in these indicators may occur depending on the severity of obesity. Liver ultrasound frequently reveals fatty liver in severely obese children.
Diagnosis
Two diagnostic criteria are commonly used for determining childhood obesity:
Body Mass Index (BMI)
BMI is calculated as weight (kg) divided by height (m2). It is recommended for use in children aged 2 years and above. A BMI between the 85th and 95th percentile for the same sex and age group is classified as overweight, while a BMI above the 95th percentile is classified as obesity.
Weight-for-Length
For children under two years old, weight-for-length is used as the evaluation standard. A weight-for-length between the 85th and 97th percentile for the same sex and age group is classified as overweight, while values above the 97th percentile are classified as obesity.
Differential Diagnosis
Obesity should be differentiated from pathological causes:
Prader-Willi Syndrome
This is characterized by peripheral obesity, short stature, intellectual disability, small hands and feet, low muscle tone, and underdeveloped external genitalia. This condition is caused by functional defects of imprinted genes in the 15q11.2-q13 chromosomal region.
Laurence-Moon-Biedl Syndrome
This presents with peripheral obesity, mild intellectual disability, retinitis pigmentosa, polydactyly, and hypogonadism.
Fröhlich Syndrome
Secondary to hypothalamic and pituitary lesions, this condition features fat distribution concentrated in the neck, submandibular region, breasts, lower extremities, perineum, and hips. Affected individuals have slender fingers and toes, short stature, and delayed or absent secondary sexual characteristics.
Other Endocrine Disorders
Disorders such as adrenocortical hyperplasia, hypothyroidism, and growth hormone deficiency may also present with increased fat deposits, but each has distinct features facilitating differentiation.
Treatment
The main therapeutic goal for obesity is to reduce energy intake and increase energy expenditure to decrease body fat levels and approach an ideal state without compromising children’s overall health and growth. Dietary therapy and exercise therapy are the primary interventions. Children with organ damage caused by obesity may require medication or surgical intervention under professional medical supervision.
Dietary Therapy
High-protein, low-fat, low-sugar, and moderate-fiber diets are recommended, considering children’s growth and the long-term nature of obesity treatment. Healthy dietary habits, such as avoiding skipping breakfast or overeating at dinner, not consuming late-night snacks or excessive snacks, and eating slowly with thorough chewing, are beneficial for weight loss. Using food as a reward should be avoided. Parents, siblings, and peers can adopt balanced dietary and healthy eating habits to create a supportive environment.
Exercise Therapy
Appropriate physical activity promotes fat breakdown, reduces insulin secretion, decreases fat synthesis, and increases protein synthesis, thereby aiding muscle development. Activities that children enjoy and can sustain, such as morning runs or exercises, can be encouraged, with a minimum of 30 minutes of daily physical activity. Physical exertion should be enjoyable and not cause fatigue, and activity levels should increase gradually.
Psychological Therapy
Support can be provided to help children adhere to dietary control and enhance physical activity, boosting confidence in weight management. Psychological and behavioral issues may limit social opportunities for obese children, establishing a vicious cycle that decreases social adaptability. Regular encouragement to participate in group activities can help address loneliness and low self-esteem, fostering the development of a healthy lifestyle and self-management skills.
Pharmacological Therapy
Medication is generally not recommended for children.
Prevention
Promoting health education, maintaining balanced diets, and increasing physical activity play key roles in obesity prevention.
Preventive measures should begin during pregnancy. The World Health Organization recommends addressing childhood obesity from the fetal stage, considering its prevention a collective social responsibility.