Nutrition

******We were not really tested in detail on this lecture except what was highlighted in purple

Nutrition

• Our diet provides essential nutrients that are fundamental for health and energy. These include sources we have previously discussed such as carbohydrates, fats, and proteins.

• Essential Fatty Acids: The body cannot synthesize certain fatty acids and must acquire them from the diet. Notable examples include:

  • Linolenate and Linoleate: These serve as precursors to prostaglandins. The human body lacks the enzymes required to create the specific carbon-carbon double bonds found in these molecules.

• Essential Amino Acids: There are specific amino acids that must be obtained through dietary intake because the body cannot synthesize them PVT TIM HALL (typically representing Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, and Lysine).

• Vitamins and Minerals: These are micronutrients required for various metabolic processes.

Recommended Daily Allowances (RDA)

• The RDA is defined not merely as the minimum amount required to prevent deficiency, but includes a safety margin above the minimum needs to ensure the health of the general population.

• RDAs are not static; they vary based on several factors:

  • Age: Nutritional needs change with growth and development. For instance, an adult requires approximately $0.8\,g$ of protein per kilogram of body weight ($0.8\,g\,\text{protein}/kg$), whereas infants require approximately $2.0\,g\,\text{protein}/kg$ to support rapid growth and building of protein tissue.

  • Sex: Male RDAs are generally about $20\%$ greater than those for women, with the exception of Iron, for which women often require more.

  • Other Physiological States:

    • Pregnancy: Increases RDAs by approximately $20\text{--}30\%$ to support the developing fetus and the stress on the mother's body.

    • Illness: Increases certain RDAs to help the body fight off infection and repair tissues.

Intake

• Caloric intake averages vary by body size and sex:

  • Average Adult Male ($70\,kg$): $2900\,kcal\,day^{-1}$.

  • Average Adult Female ($50\,kg$): $2100\,kcal\,day^{-1}$.

• These values represent target values for good health.

• Distribution of Energy Usage:

  • Basal Metabolic Rate (BMR): Accounts for approximately $60\%$ of total calories ($1800\,kcal$ for males, $1300\,kcal$ for females). This energy supports basic body functions.

  • Thermic Effect (Body Heat): Accounts for approximately $10\%$ of total calories ($290\,kcal$ for males, $210\,kcal$ for females).

  • Physical Activity: Accounts for approximately $30\%$ of total calories ($870\,kcal$ for males, $630\,kcal$ for females). This category is the most variable and can increase significantly with activities like walking.

Energy source

• The energy in our diet is supplied by specific macronutrients, each with different energy densities:

  • Carbohydrates: Yields $4\,kcal\,g^{-1}$. Current US intake is $46\%$; recommended is $58\%$.

  • Protein: Yields $4\,kcal\,g^{-1}$. Both current and recommended intake is $12\%$.

  • Fat: Yields $9\,kcal\,g^{-1}$. Current US intake is $42\%$; recommended is $30\%$.

  • Alcohol: Mentioned as providing $7\,kcal\,g^{-1}$.

Fats, Carbohydrates, and Fiber

• Dietary Fat:

  • $90\%$ of dietary fat consists of triglycerides.

  • Fat serves as a source of energy, essential fatty acids, and fat-soluble vitamins.

  • Animal fatty acids are generally more saturated than plant fats and contain more energy.

  • Recommended fat distribution: $10\%$ polyunsaturated, $10\%$ monounsaturated, and $10\%$ saturated fat.

• Carbohydrates:

  • Monosaccharides: Found in fruits, corn, and honey.

  • Disaccharides: Found in molasses, milk, and beer.

  • Polysaccharides: Found in grains, potatoes, beans, and vegetables.

  • The average person consumes approximately $80\,lbs$ of sugar per year, which accounts for ~$11\%$ of daily calories.

• Fiber:

  • Includes Cellulose, Lignin, and Pectin.

  • Fiber does not provide energy but is essential because it:

    1. Softens stool.

    2. Promotes intestinal motility.

    3. Decreases absorption of toxic compounds.

    4. Decreases the risk of colon cancer.

Protein

• Proteins are needed primarily to supply essential amino acids for protein synthesis, though they can also supply calories.

• Dietary sources are evaluated on their ability to supply all ten essential amino acids ("PVT TIM HALL"):

  • Gold Standard: Egg albumin (egg whites) has a biological value of $100$.

  • High Quality: Meat, poultry, fish, and milk range from $85$ to $100$.

  • Plant Proteins: generally lower, around $50$ to $70$ (e.g., Potato = $67$, Whole wheat bread = $67$, Beans = $30\text{--}40$).

• Vegetarians must use appropriate combinations of plant sources to ensure they receive all essential amino acids.

Body Composition

• Water: $55\%$ of total body mass.

  • Intracellular fluid: $65\%$ of total water.

  • Extracellular fluid: $35\%$ of total water (composed of $75\%$ interstitial fluid and $25\%$ plasma).

• Protein: $19\%$.

• Fat: $19\%$.

• Minerals and Inorganics: $7\%$ (including bone).

• Carbohydrate: < 1\% (stored as glycogen in liver and muscle).

• Vitamins: < 0.01\%.

Weight Loss Planning for "Biff"

Subject Profile

• Age: $30$ years old.

• Height: $188\,cm$.

• Current Weight: $132\,kg$.

• Goal Weight: $86\,kg$ (Ideal weight).

• Timeline: $8$ months ($244\,days$).

• Lifestyle: Sedentary.

• Current Intake: $140\,g$ Protein, $120\,g$ Fat, $590\,g$ Carbohydrate.

Calculation Formulas

• BMR: $Weight\,(kg) \times 24\,kcal\,kg^{-1}$.

• Activity Multipliers:

  • Sedentary: add $30\%$ of BMR.

  • Moderately Active: add $40\%$ of BMR.

  • Active: add $50\%$ of BMR.

• Recommended Energy Distribution:

  • Protein: $15\%$

  • Carbohydrate: $55\%$

  • Fat: $30\%$

Step-by-Step Weight Loss Plan

1. Identify Total Weight Loss Needed:

   • $132\,kg - 86\,kg = 46\,kg$ of fat total.

2. Identify Energy Deficit Required:

   • Total energy to lose: $46000\,g \times 9\,kcal\,g^{-1} = 414000\,kcal$.

   • Daily deficit: $\frac{414000\,kcal}{244\,days} \approx 1700\,kcal\,day^{-1}$.

3. Calculate Current Maintenance Calories:

   • BMR: $132\,kg \times 24\,kcal\,kg^{-1} = 3168\,kcal$.

   • Activity (Sedentary): $3168 \times 0.30 = 950\,kcal$.

   • Total Maintenance: $3168 + 950 = 4118\,kcal\,day^{-1}$.

4. Determine New Caloric Intake:

   • $4118\,kcal\,day^{-1} - 1700\,kcal\,day^{-1} \approx 2418\,kcal\,day^{-1}$ (rounded to $2400\,kcal$).

5. Calculate Target Macronutrient Grams for New Diet:

   • Protein ($15\%$): $\frac{2400 \times 0.15}{4\,kcal\,g^{-1}} = 90\,g$.

   • Carbohydrates ($55\%$): $\frac{2400 \times 0.55}{4\,kcal\,g^{-1}} = 330\,g$.

   • Fat ($30\%$): $\frac{2400 \times 0.30}{9\,kcal\,g^{-1}} = 80\,g$.

Dietary Strategy

• Biff must cut current intake of all three macronutrients (Protein from $140\,g$ to $90\,g$, Carbohydrates from $590\,g$ to $330\,g$, and Fat from $120\,g$ to $80\,g$).

• Note: Weight loss should come from fat. This approach may cause rapid initial weight loss as the body adjusts to maintenance calories and utilizes stored glycogen (which carries water weight). It is recommended to recalculate needs every two weeks as weight changes.