Parameters to detect overnutrition

Introduction

Overnutrition, encompassing overweight and obesity, is defined as a condition of abnormal or excess fat deposition in the body leading to impaired health. It results from an energy imbalance where intake exceeds expenditure over time. With the rising prevalence of the "Triple Burden of Malnutrition" (undernutrition, micronutrient deficiency, and overnutrition), accurate detection of overnutrition in the pediatric age group is critical to prevent adult onset of non-communicable diseases like diabetes and hypertension.

Detection relies on a combination of anthropometric measurements, clinical assessment, and evaluation of comorbidities.

1. Anthropometric Parameters

Anthropometry is the gold standard for assessing nutritional status. The specific parameters and cut-offs vary by age group.

A. Body Mass Index (BMI)

BMI is the most commonly used measure for overweight and obesity in children and adolescents. It is an excellent proxy for direct measurement of body fat.

• Formula: $Weight(kg)/Height(m{)}^2$.
• Physiological Trajectory: BMI changes with age. It is low at birth ($\approx$13 kg/m²), increases to $\approx$17kg/m²atoneyear,decreasestoanadir($\approx$15 kg/m²) at 6 years, and increases again toward adulthood.
• Adiposity Rebound: The point where body fat is at its lowest (usually around 5.5 years) before increasing is called adiposity rebound. Early adiposity rebound is a risk factor for adult obesity.

Cut-offs and Classification:

• Children < 5 Years (WHO Growth Standards):

  • BMI is generally not the primary indicator for infants < 2 years, but Weight-for-Height is preferred. However, for children older than 2 years:
  • Overweight: BMI > 85th percentile.
  • Obesity: BMI > 95th percentile.

• Children 5–19 Years (WHO/IOTF Reference):

  • Overweight: BMI > +1 SD (equivalent to BMI 25 kg/m² at 18 years).
  • Obesity: BMI > +2 SD (equivalent to BMI 30 kg/m² at 18 years).
  • Severe Obesity: BMI $\ge$ 120% of the 95th percentile or $\ge$ 35 kg/m².

• CDC 2000 Guidelines (2–20 years):

  • Normal: 5th to 85th percentile.
  • Overweight: 85th to 95th percentile.
  • Obese: $\ge$ 95th percentile.

• ELIZ Health Path for Adolescents:

  • A simplified chart designed for Indian adolescents that incorporates weight, height, and BMI.
  • Overweight: BMI > 22.
  • Obesity: BMI > 25 (This lower cut-off reflects the higher risk of metabolic complications in Indian phenotypes at lower BMIs).

B. Weight-for-Height/Length

This is the primary parameter for children under 5 years of age.

• Definition: Compares the child's weight to the median weight of a child of the same length/height in the reference population.
• Interpretation (WHO Standards):
  • Overweight: > +2 SD (Z-score).
  • Obesity: > +3 SD (Z-score).
  • Broca’s Index (Older Children/Adults): Ideal weight (kg) = Height (cm) - 100. Weight-for-height > 120% of ideal is considered obesity.

C. Skin Fold Thickness (SFT)

SFT measures subcutaneous fat and correlates well with total body fat.

• Sites: Triceps, subscapular, biceps, and supra-iliac regions.
• Interpretation: Values > 85th percentile for age and sex indicate risk for obesity or overweight.
• Utility: Useful to distinguish between heavy weight due to muscularity versus adiposity.

D. Waist Circumference and Waist-to-Hip Ratio (WHR)

These parameters assess body fat distribution (central vs. peripheral obesity).

• Significance: Central or "Apple-shaped" obesity (android) carries a higher risk for cardiovascular disease and diabetes compared to "Pear-shaped" obesity (gynoid).
• Cut-offs: A Waist-to-Hip Ratio (WHR) > 0.9 in males and > 0.8 in females indicates significant health risk.

E. Mid-Upper Arm Circumference (MUAC)

• While primarily used for undernutrition screening, MUAC is also listed as a measure applicable to overnutrition. High values indicate excess fat and muscle mass.

2. Clinical Assessment

Clinical evaluation helps distinguish between simple (constitutional) obesity and pathological causes (endocrine/syndromic), and identifies comorbidities.

A. Growth Pattern and History

• Constitutional Obesity: Most common type. Associated with tall stature and advanced bone age (growing fast). The child looks "big" for age.
• Pathological/Endocrine Obesity: Associated with short stature and delayed bone age (e.g., Cushing syndrome, Hypothyroidism).
• Drug History: Use of medications like atypical antipsychotics which increase appetite.
• Developmental History: History of intrauterine growth retardation (IUGR) followed by rapid catch-up growth is a risk factor for central obesity and insulin resistance (Barker hypothesis).

B. Physical Signs of Comorbidities

• Skin:
  • Acanthosis Nigricans: Dark, velvety pigmentation on the neck and axilla, indicating insulin resistance and Type 2 Diabetes.
  • Striae: Purple striae suggest Cushing syndrome.
  • Intertrigo: Fungal infections in skin folds due to hygiene issues.
• Respiratory:
  • Pickwickian Syndrome: Severe obesity causing alveolar hypoventilation, somnolence, and cyanosis.
  • Obstructive Sleep Apnea: Snoring and daytime sleepiness.
• Orthopedic:
  • Slipped Capital Femoral Epiphysis (SCFE): Hip or knee pain.
  • Blount Disease: Bowing of legs (tibia vara).
• Endocrine/Reproductive:
  • Polycystic Ovarian Syndrome (PCOS): Hirsutism, acne, and menstrual irregularities in adolescent girls.
  • Genitalia: In constitutional obesity, genitalia may appear disproportionately small because they are embedded in suprapubic fat.

3. Dietary and Lifestyle Assessment

Assessment of "Energy Balance" is crucial to determine the etiology.

• Dietary Intake:
  • 24-Hour Recall: Assessment of caloric intake, frequency of meals, and portion sizes.
  • Obesogenic Foods: Identification of high-fat, high-sugar consumption (junk foods, sugar-sweetened beverages/colas).
  • Feeding Habits: History of "mindless snacking," grazing, or eating while watching TV.
• Physical Activity:
  • Assessment of sedentary behavior, specifically screen time (TV, mobile, computer) and lack of outdoor play.
  • Imbalance: Even a small excess of 25 kcal/day over expenditure can lead to obesity over time.

4. Laboratory Parameters (Screening for Metabolic Syndrome)

Children with BMI $\ge$ 85th percentile (Overweight) with risk factors, or $\ge$ 95th percentile (Obese) require screening for metabolic complications.

• Lipid Profile: To detect dyslipidemia.
  • Elevated Triglycerides (> 150 mg/dl).
  • Low HDL Cholesterol (< 40 mg/dl).
  • Elevated LDL Cholesterol.
• Glucose Homeostasis:
  • Fasting Blood Glucose: To screen for pre-diabetes (Impaired Fasting Glucose) or Diabetes.
  • Fasting Insulin: High levels indicate hyperinsulinism and insulin resistance.
• Liver Function Tests:
  • ALT/AST: Elevated transaminases suggest Non-Alcoholic Fatty Liver Disease (NAFLD).
• Blood Pressure: To detect hypertension, which correlates with BMI.

Summary of Diagnostic Criteria