Topic 13 — Human Nutrition: Nutrients, Deficiency Disorders, Malnutrition and Obesity

Connect the major nutrition concepts into one rapid-revision framework: adequate intake → normal function, deficiency → undernutrition, and chronic excess → obesity.

1. THE TOPIC IN ONE CONNECTED FLOW

Nutrition is a balance between what the body receives and what it requires. Macronutrients mainly provide energy and structural material, while vitamins and minerals support specific metabolic functions. When intake and requirements are appropriately matched, growth and health are maintained; inadequate intake produces deficiency and undernutrition, whereas prolonged excess energy intake promotes obesity.

Dietary Intake

Carbohydrate, protein, fat, vitamins, minerals, fibre and water

→

Nutrient Quality

Adequacy, variety, bioavailability and appropriate proportions

→

Normal Function

Energy, growth, tissue repair, metabolism and physiological regulation

→

Intake–Need Imbalance

Deficiency or sustained excess compared with body requirements

→

Nutritional Disorder

Micronutrient deficiency, PEM or excess adiposity

→

Control & Outcome

Assessment, balanced intake, prevention, rehabilitation and long-term risk reduction

Deficiency pathway

Low intake or poor utilization → deficient energy/protein or micronutrients → impaired growth and function → wasting, stunting, PEM or specific deficiency disease.

Excess pathway

Energy intake persistently exceeds expenditure → triglyceride storage increases → adipose tissue expands → obesity and metabolic or mechanical complications.

2. KEY CLINICAL CONNECTIONS

Micronutrient Clues

Vitamin A deficiency → impaired retinal/epithelial function → night blindness and xerophthalmia

→
Vitamin D deficiency → impaired bone mineralization → rickets or osteomalacia

→
Iron deficiency → reduced hemoglobin synthesis → microcytic hypochromic anemia

PEM Pattern Recognition

Prolonged total energy deficit → loss of fat and muscle → severe wasting without edema = marasmus

→
Severe edematous malnutrition → edema with wasting and possible fatty liver = kwashiorkor

Assessment & Control

Low weight-for-height → wasting → recent/acute nutritional depletion

→
Low height-for-age → stunting → chronic growth failure

→
Early detection + feeding improvement + infection control → reduced malnutrition burden

Obesity Risk Chain

Positive energy balance → adipose accumulation

→
visceral adiposity → insulin resistance and dyslipidemia

→
diabetes, hypertension, fatty liver and cardiovascular risk

3. AIM HIGH-YIELD INTEGRATION REVIEW

⭐ Balanced diet → adequate energy plus appropriate macro- and micronutrients → normal growth and physiological function.

Carbohydrate and protein provide about 4 kcal/g, while fat provides about 9 kcal/g → fat is the most energy-dense macronutrient.

⭐ Fat malabsorption → reduced absorption of vitamins A, D, E and K → characteristic fat-soluble vitamin deficiencies.

Vitamin B12 and folate deficiency both cause megaloblastic anemia → neurological dysfunction particularly favors vitamin B12 deficiency.

⭐ Wasting = low weight-for-height → acute/recent undernutrition; stunting = low height-for-age → chronic undernutrition.

Malnutrition → impaired immunity → infection → reduced intake and increased losses → worsening malnutrition.

BMI estimates weight relative to height but not body-fat distribution → central adiposity provides additional metabolic-risk information.

⭐ Sustained positive energy balance → obesity → metabolic and mechanical complications → prevention requires sustainable diet, activity and supportive environments.

AIM Exam Trap: Adequate calorie intake does not necessarily mean adequate nutrition. A calorie-sufficient diet can still be deficient in protein, vitamins, minerals or fibre.

Topic 13 — Human Nutrition: Nutrients, Deficiency Disorders, Malnutrition and Obesity

1. THE TOPIC IN ONE CONNECTED FLOW

2. KEY CLINICAL CONNECTIONS

3. AIM HIGH-YIELD INTEGRATION REVIEW

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