Malnutrition

Definition

Classification

1. Primary vs Secondary

2. WHO Categories of Malnutrition

• Wasting — low weight-for-height (acute undernutrition)
• Stunting — low height-for-age (chronic undernutrition)
• Underweight — low weight-for-age
• Micronutrient deficiency — inadequate vitamins/minerals
• Overweight/obesity — excess caloric intake
• Diet-related NCDs — cardiovascular disease, diabetes, cancers

Severe Acute Malnutrition (SAM)

~50 million children worldwide are affected; 45% of deaths in children under 5 in low-resource countries are attributable to undernutrition.

Marasmus (Calorie Deficiency)

• Severe deficiency of both calories and protein
• The somatic protein compartment (skeletal muscle) is depleted; the visceral compartment is relatively spared
• Serum albumin is normal or near-normal
• Body adapts by catabolizing muscle → amino acids used as fuel
• Subcutaneous fat is also mobilized
• Clinical features: severe emaciation, "skin and bones" appearance, "old man face," large head relative to body, "baggy pants" skin on limbs, concurrent vitamin deficiencies, immune deficiency (especially T-cell), anemia

Kwashiorkor (Protein Deficiency)

• Protein deprivation is relatively greater than caloric deficit
• Classically seen in children weaned early onto a carbohydrate-only diet
• The visceral protein compartment is severely depleted → hypoalbuminemia → edema
• Clinical features:
  • Bilateral peripheral edema (starts in dependent areas, ascends)
  • "Flaky paint" skin depigmentation with areas of breakdown
  • Pale, reddish-yellow ("flag sign") hair
  • Enlarged, fatty liver (impaired lipoprotein synthesis)
  • Apathy, listlessness, anorexia
  • Distended abdomen
  • NO ascites typically (unlike hepatic disease)

Marasmic-Kwashiorkor

Clinical Images

Pathophysiology of Starvation

• Fat replaces glucose as the primary fuel; ketosis develops rapidly
• BMR declines → hypothermia and fatigue
• Cortisol ↑, insulin ↓, thyroid hormone ↓
• Prolonged starvation → near-complete fat depletion, muscle mass cut by ~half
• Hypokalemia → rapid muscle fatigue, cardiac arrhythmia (major cause of death in anorexia nervosa)
• Cardiac: bradycardia, ↓ stroke volume, hypotension
• Pulmonary: decreased respiratory muscle mass, electrolyte disturbances
• GI: villous atrophy, blunted microvilli, disaccharidase deficiency (esp. lactase), impaired pancreatic/biliary secretion → complicates refeeding
• Immune: lymphoid atrophy, impaired cell-mediated immunity → opportunistic infections
• Bone marrow: hypoplasia → anemia (microcytic if Fe-deficient; mixed if folate co-deficient)
• Brain: cerebral atrophy in infants; delayed cognitive development with lifelong consequences

Common Causes

Diagnosis

Anthropometric Measurements

• Mid-upper arm circumference (MUAC): most practical field tool for children 6–59 months and pregnant women
• Weight-for-height Z-score (WHZ): wasting if ≥2 SD below median; SAM if ≥3 SD
• Height-for-age Z-score (HAZ): stunting if ≥2 SD below median
• BMI: <18.5 kg/m² = moderate secondary malnutrition; <15 kg/m² = severe

Laboratory

• Serum albumin and prealbumin — useful for visceral protein compartment assessment but are acute-phase reactants and non-specific
• Transferrin levels
• Skinfold thickness (subcutaneous fat stores)
• Mid-arm circumference (somatic muscle mass)
• Note: No single reliable lab test; grip strength is the best single clinical measure in secondary malnutrition

Differential Diagnosis of Edema in Kwashiorkor

Treatment

Uncomplicated SAM (Outpatient)

• Ready-to-use therapeutic food (RUTF): fortified peanut paste (~30 g under directly observed therapy)
• Empiric oral antibiotics (1 week) — shown to decrease mortality, improve nutritional recovery, reduce hospitalization
• Community-based programs have superior outcomes to inpatient care; this is now the international standard of care

Complicated SAM (Inpatient)

1. Treat/prevent hypoglycemia
2. Treat/prevent hypothermia
3. Treat/prevent dehydration
4. Correct electrolyte imbalances
5. Treat/prevent infection
6. Correct micronutrient deficiencies
7. Cautious initial feeding (F-75 formula — 75 kcal/100 mL)
8. Transition to catch-up growth (F-100 formula — 100 kcal/100 mL)
9. Sensory stimulation and emotional support
10. Prepare for follow-up

Caution — Refeeding syndrome: Rapid reintroduction of carbohydrates can precipitate severe hypophosphatemia, hypokalemia, and hypomagnesemia → cardiac arrhythmia and death. Start feeds slowly.

Lactose intolerance in kwashiorkor: Intestinal mucosal atrophy causes disaccharidase (lactase) deficiency; avoid full-strength milk-based formulas initially — these changes are reversible with treatment.

Stunting

• Limited reversibility once established (first 1000 days are critical)
• Improved dietary quality/diversity (complete protein), immunizations, vitamin A supplementation, deworming, HIV testing, improved sanitation

Secondary Malnutrition

• Treat underlying disease
• Nutritional rehabilitation in parallel with treatment of primary illness
• Wound healing is impaired with albumin <2.0 g/dL; protein supplements can reverse this

Consequences

• Increased susceptibility to infection (immunodeficiency)
• Impaired wound healing and surgical risk
• Cardiac arrhythmia and sudden death (hypokalemia)
• Cerebral atrophy, cognitive impairment
• Growth failure — physical and mental
• Metabolic syndrome and obesity paradox in adult survivors of childhood malnutrition
• Increased healthcare costs and readmission rates

Key Numbers (WHO, 2022)

• 149 million children under 5 are stunted
• 45 million are wasted
• 37 million are overweight/obese
• 2.5 billion adults are overweight; 890 million are obese
• 390 million adults are underweight