Macronutrients and Energy Requirements

Overview & Carbs - Sweet Energy Source

• Macronutrients: Carbs, Proteins, Fats - fuel body, support growth & metabolism.
• Atwater Factors (Energy):
  • Carbs: 4 kcal/g
  • Proteins: 4 kcal/g
  • Fats: 9 kcal/g
  • Alcohol: 7 kcal/g
• Carbohydrates (CHO): Primary energy source.
  • Classification:
    • Monosaccharides: Glucose (main), Fructose, Galactose.
    • Disaccharides: Sucrose (Glu+Fru), Lactose (Glu+Gal), Maltose (Glu+Glu).
    • Polysaccharides: Starch (plant storage), Glycogen (animal storage), Cellulose (fiber).
  • RDA: 45-65% of total daily calories; minimum 130 g/day.
• Glycemic Index (GI): Ranks CHO based on blood glucose response (vs. glucose/white bread).
• Glycemic Load (GL): $GL = (GI \times \text{grams of CHO per serving}) / 100$. Assesses total glycemic effect.
• Dietary Fiber: Non-digestible polysaccharides.
  • Types:
    • Soluble (e.g., oats, apples): Forms gel; ↓cholesterol, slows glucose absorption.
    • Insoluble (e.g., wheat bran, vegetables): Adds bulk; aids motility.
  • Benefits: Gut health, satiety, ↓risk of chronic diseases.
  • RDA: 25-38 g/day.

⭐ Lactose, a disaccharide (Glucose + Galactose), requires lactase for digestion; its deficiency causes lactose intolerance.

Proteins - Body's Building Blocks

• Essential AAs: 📌 PVT TIM HALL (Phe, Val, Thr, Trp, Ile, Met, His, Arg*, Leu, Lys). *Arg: semi-essential.
• RDA (Adult): 0.8-1 g/kg body weight/day (ICMR: 1 g/kg).
• Protein Quality:
  • BV (Biological Value): $BV = \frac{\text{N retained}}{\text{N absorbed}} \times 100$. Egg BV: 100.
  • NPU (Net Protein Utilization): $NPU = \frac{\text{N retained}}{\text{N intake}} \times 100$.
  • PER (Protein Efficiency Ratio): $PER = \frac{\text{Weight gain (g)}}{\text{Protein consumed (g)}}$.
  • Chemical Score: Vs. reference protein; finds limiting AA.
• Nitrogen Balance:
  • Positive: N intake > N output (Growth, pregnancy, recovery).
  • Negative: N intake < N output (Starvation, burns, illness).
  • Equilibrium: N intake = N output (Healthy adult).
• PEM (Protein-Energy Malnutrition):
  • Kwashiorkor: Edema, ↓ serum albumin, fatty liver.
  • Marasmus: Severe wasting, no edema, alert & irritable.

⭐ Kwashiorkor is characterized by edema and hypoalbuminemia, while Marasmus presents with severe muscle wasting but typically normal or slightly decreased albumin and no edema.

Fats & Energy - Dense Fuel & Dynamics

• Lipids: TGs (storage), Phospholipids (membranes), Sterols (cholesterol).
• RDA (Fats): 20-35% total energy. SFA <10%; PUFA 6-11% (ω-6: 5-8%, ω-3: 1-2%); MUFA fills gap.
• Essential Fatty Acids (EFAs):
  • LA (ω-6): Safflower oil. Def: Scaly skin.
  • ALA (ω-3): Flaxseed. Def: Neuro/visual.
• Fatty Acid Types:
  • SFA (butter): ↑LDL.
  • MUFA (olive oil): ↓LDL, ↑HDL.
  • PUFA (fish oil): ↓LDL.
• Trans Fats (vanaspati): ↑LDL, ↓HDL, CVD risk. <1% TEE.
• Energy Metabolism (TEE Components):
  • BMR: 60-75% TEE. Factors: Age, sex, BSA, thyroid.
  • TEF: ~10% TEE. Protein highest (20-30%).
  • Physical Activity: 15-30% TEE.
• Respiratory Quotient (RQ): $RQ = \frac{\text{CO}_2 \text{ produced}}{\text{O}_2 \text{ consumed}}$
  • Values: Carbs 1.0; Protein ~0.8; Fats ~0.7; Mixed ~0.85.

  ⭐ RQ for fat is 0.7. RQ > 1.0 suggests lipogenesis/overfeeding.

High‑Yield Points - ⚡ Biggest Takeaways

• Respiratory Quotient (RQ): Carbohydrates 1.0, Fats ~0.7, Proteins ~0.8; Mixed diet ~0.85.
• Basal Metabolic Rate (BMR) influenced by age, sex, lean body mass, body surface area, thyroid status.
• Specific Dynamic Action (SDA) highest for Proteins (30%), lowest for Fats (4%).
• PEM: Kwashiorkor (edema, ↓albumin, fatty liver) vs. Marasmus (wasting, alert).
• Essential fatty acids: Linoleic (ω-6) & α-linolenic (ω-3) are vital.
• Nitrogen balance: 1 g N = 6.25 g protein. Positive in growth, pregnancy.
• Energy values: Carbs/Proteins 4 kcal/g, Fats 9 kcal/g, Alcohol 7 kcal/g.