Obesity, Malnutrition & Micronutrient Disorders

Forfar & Arneil 7th Edition · Obesity: prevalence, diagnosis, consequences, causes, treatment, secondary obesity · Malnutrition: classification, clinical features, lab investigations, management, prevention · Micronutrients: iron, copper, iodine, zinc, vitamin A, vitamin D, folate – deficiency & excess
📌 Key principles: Obesity is diagnosed by BMI >95th centile; primary (exogenous) most common. Malnutrition: marasmus (energy deficiency, no oedema), kwashiorkor (protein deficiency, oedema). Iron deficiency most common micronutrient deficiency worldwide. Vitamin A deficiency causes xerophthalmia; excess causes toxicity. Vitamin D deficiency causes rickets; excess causes hypercalcaemia.

📖 Obesity, Malnutrition & Micronutrient Disorders

🍔 Obesity – diagnosis & consequences
BMI >95th centile (≥2y). Comorbidities: insulin resistance, T2DM, hypertension, dyslipidaemia, NAFLD, sleep apnoea, psychosocial issues. Primary (exogenous) most common; secondary (endocrine, genetic).
🥀 Malnutrition – classification
Marasmus (energy deficiency): severe wasting, no oedema, low weight-for-height. Kwashiorkor (protein deficiency): oedema, fatty liver, skin lesions, apathy. Marasmic-kwashiorkor (both).
🩸 Iron – deficiency & excess
Deficiency: microcytic anaemia, pica, koilonychia, cognitive impairment. Excess: iron overload (haemochromatosis, multiple transfusions) → organ damage.
🧂 Iodine & Zinc
Iodine deficiency: goitre, hypothyroidism, cretinism. Excess: iodism. Zinc deficiency: growth failure, periorificial rash, alopecia, diarrhoea, immune dysfunction.
🌿 Vitamins A, D, Folate
Vitamin A deficiency: xerophthalmia, night blindness, Bitot spots, immune impairment. Excess: hypervitaminosis A (hepatotoxicity, pseudotumour cerebri). Vitamin D deficiency: rickets, hypocalcaemia. Excess: hypercalcaemia, nephrocalcinosis. Folate deficiency: macrocytic anaemia, neural tube defects (pregnancy).
📊 Key investigations: BMI, waist circumference (obesity). Plasma ferritin, TIBC, Hb (iron). 25-OHD (vitamin D). Zinc, copper, iodine (urinary iodine). Serum folate, RBC folate. Thyroid function (iodine).

🔍 Clinical approach to obesity & malnutrition

1
Obesity assessment – BMI >95th centile (≥2y). Waist circumference (metabolic risk). Assess comorbidities: acanthosis nigricans (insulin resistance), hypertension, dyslipidaemia, NAFLD (ALT), sleep apnoea, psychosocial.
2
Secondary obesity causes – Endocrine: Cushing syndrome (hypertension, striae, growth failure), hypothyroidism (short stature, fatigue), pseudohypoparathyroidism. Genetic syndromes: Prader-Willi (hyperphagia, hypotonia), Bardet-Biedl (retinitis pigmentosa, polydactyly), leptin deficiency.
3
Malnutrition – classification by WHO – Severe acute malnutrition (SAM): weight-for-height <-3 SD or MUAC <11.5 cm or bilateral oedema. Moderate acute malnutrition (MAM): weight-for-height -2 to -3 SD or MUAC 11.5-12.4 cm. Stunting: height-for-age <-2 SD.
4
Clinical features of marasmus vs kwashiorkor – Marasmus: severe wasting, old man face, no oedema. Kwashiorkor: oedema (feet, hands, face), fatty liver, skin desquamation, flag sign (hair discolouration), apathy.
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Micronutrient deficiency clinical clues – Pallor, koilonychia (iron). Angular stomatitis, glossitis (iron/B vitamins). Periorificial rash, alopecia (zinc). Bitot spots, night blindness (vitamin A). Rickets (vitamin D). Goitre (iodine).
📌 Clinical pearl: In a child with obesity and short stature, consider endocrine causes (Cushing syndrome, hypothyroidism). In a child with obesity and learning difficulties, consider Prader-Willi syndrome (hyperphagia, hypotonia, small hands/feet).

📋 Stepwise management of obesity, malnutrition & micronutrient disorders

1
Childhood obesity – lifestyle intervention – Dietary: reduce sugar-sweetened beverages, portion control, increase vegetables/fruit, limit screen time. Physical activity: ≥60 minutes/day moderate-vigorous. Behavioural therapy: goal setting, self-monitoring. Pharmacotherapy (orlistat) for adolescents with severe obesity. Bariatric surgery for BMI >40 with comorbidities.
2
Severe acute malnutrition (SAM) – WHO 10 steps – Stabilisation phase (F-75): treat hypoglycaemia, hypothermia, dehydration, infection, electrolytes. Rehabilitation phase (F-100 or RUTF). Monitor for refeeding syndrome.
3
Iron deficiency anaemia – Oral ferrous sulphate 3-6 mg/kg/day elemental iron. Continue for 3 months after Hb normalisation. Dietary advice: red meat, fortified cereals, vitamin C. Treat underlying cause (excessive cow's milk, blood loss).
4
Vitamin D deficiency rickets – Stoss therapy: 150,000-300,000 IU vitamin D orally once (or 2000-4000 IU/day for 3 months). Calcium supplementation. Maintenance 400 IU/day. Monitor serum calcium, ALP.
5
Vitamin A deficiency (xerophthalmia) – High-dose vitamin A: 200,000 IU (12-59 months) orally immediately, next day, then at least 2 weeks later. Prevent with 6-monthly supplementation in endemic areas.
6
Zinc deficiency – Oral zinc sulphate 1-2 mg/kg/day elemental zinc. Acrodermatitis enteropathica requires lifelong zinc supplementation (ZIP4 mutation).
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Iodine deficiency – Iodised salt, seafood, dairy. Severe deficiency: oral iodine (potassium iodide) or thyroxine if hypothyroid. Prevent cretinism.
⚠️ WHO 10 steps for SAM: 1) Hypoglycaemia, 2) Hypothermia, 3) Dehydration, 4) Electrolytes, 5) Infection, 6) Micronutrients, 7) Initiate feeding (F-75), 8) Catch-up growth (F-100/RUTF), 9) Sensory stimulation, 10) Follow-up.

🧠 Reflex prompts: obesity, malnutrition & micronutrients

📏 A 10-year-old boy with BMI 30 kg/m² (98th centile), acanthosis nigricans. Most appropriate first step?
Lifestyle intervention (diet, exercise). Screen for prediabetes (HbA1c, fasting glucose), dyslipidaemia, NAFLD (ALT).
⚠️ A child with obesity, short stature, hypertension, and purple striae. Most likely cause?
Cushing syndrome (endogenous or exogenous steroids). Screen with overnight dexamethasone suppression test.
🍼 A 2-year-old with severe wasting, no oedema, "old man" facies. Diagnosis?
Marasmus (energy deficiency). Treat with high-energy feeds (F-75 then F-100/RUTF).
🦶 A 3-year-old with bilateral pitting oedema, skin desquamation, flag sign (discoloured hair). Diagnosis?
Kwashiorkor (protein deficiency oedema). Treat with F-75 (low protein initially) then high-protein rehabilitation.
🩸 A 9-month-old with pallor, pica, koilonychia, Hb 6.5 g/dL, MCV 55 fL. Most likely deficiency?
Iron deficiency. Oral ferrous sulphate 3-6 mg/kg/day. Limit cow's milk (<500 ml/day).
👁️ A 4-year-old with night blindness and Bitot spots. Which vitamin deficiency?
Vitamin A deficiency. High-dose vitamin A (200,000 IU stat). Prevent with 6-monthly supplementation.
🦴 A 15-month-old with bowed legs, rachitic rosary, hypocalcaemia, low 25-OHD. Diagnosis?
Vitamin D deficiency rickets. Stoss vitamin D + calcium. Daily maintenance 400 IU.
🧴 A child with periorificial dermatitis (around mouth, anus), alopecia, diarrhoea, and poor growth. Which mineral deficiency?
Zinc deficiency. Acrodermatitis enteropathica (inherited) or acquired. Zinc sulphate supplementation.
🧂 A child with goitre, hypothyroidism, and low urinary iodine. Most likely?
Iodine deficiency. Iodised salt, seafood, potassium iodide. Prevent cretinism in pregnancy.
🩸 A macrocytic anaemia (MCV 105 fL) with hypersegmented neutrophils, normal B12, low folate. Diagnosis?
Folate deficiency. Causes: poor intake (goat's milk), malabsorption, increased demand. Folic acid 1-5 mg/day.