Macronutrients and Energy Requirements

Macronutrients and Energy Requirements

Macronutrients and Energy Requirements

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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: Carbohydrate Classification Concept Map
      • 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). Nitrogen balance states
  • 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. Essential Fatty Acids and Dietary Sources
  • 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.

Practice Questions: Macronutrients and Energy Requirements

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What does the glycemic index of a starchy food measure?

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Flashcards: Macronutrients and Energy Requirements

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Correct sequence of specific dynamic values (SDA) of proteins _____ lipids > carbohydrates.

TAP TO REVEAL ANSWER

Correct sequence of specific dynamic values (SDA) of proteins _____ lipids > carbohydrates.

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