Nutrition Fundamentals
The basic science of nutrition: calories, macros, and how food fuels your body.
Energy Balance
Calories Explained
A calorie is a unit of energy. Your body needs energy to:
- Keep organs functioning (60-75% of daily burn)
- Digest food (5-10%)
- Move and exercise (15-30%)
- Everything else
Total Daily Energy Expenditure (TDEE) = BMR + TEF + Activity
| Component | What It Is | % of Total |
|---|---|---|
| BMR (Basal Metabolic Rate) | Energy for basic life functions | 60-75% |
| TEF (Thermic Effect of Food) | Energy to digest food | 5-10% |
| Activity | Exercise and daily movement | 15-30% |
Calculating Your Needs
Step 1: Estimate BMR
Mifflin-St Jeor equation:
- Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
Step 2: Apply Activity Multiplier
| Activity Level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | 1.2 |
| Lightly active (light exercise 1-3 days/week) | 1.375 |
| Moderately active (moderate exercise 3-5 days/week) | 1.55 |
| Very active (hard exercise 6-7 days/week) | 1.725 |
| Extremely active (physical job + hard exercise) | 1.9 |
Example:
- 180 lb (82 kg), 5'10" (178 cm), 40-year-old man
- BMR: (10 × 82) + (6.25 × 178) - (5 × 40) + 5 = 1,738 calories
- Moderately active: 1,738 × 1.55 = 2,694 calories/day
Weight Management
| Goal | Calorie Strategy |
|---|---|
| Lose weight | TDEE - 300 to 500 calories |
| Maintain weight | Eat at TDEE |
| Gain muscle | TDEE + 200 to 300 calories |
Rates:
- Fat loss: 0.5-1% bodyweight per week
- Muscle gain: 0.5-1 lb per month (natural)
Macronutrients
The three macros provide calories:
| Macro | Calories/gram | Primary Function |
|---|---|---|
| Protein | 4 | Build and repair tissue |
| Carbohydrates | 4 | Primary energy source |
| Fat | 9 | Hormones, cell function, energy |
Protein
What it does:
- Builds and repairs muscle
- Makes enzymes and hormones
- Supports immune function
- Provides satiety
How much:
- Sedentary: 0.36g/lb (RDA minimum)
- Active/building muscle: 0.7-1g/lb
- Dieting: 1g/lb (preserves muscle)
Best sources:
- Meat, poultry, fish
- Eggs
- Greek yogurt
- Cottage cheese
- Legumes (incomplete but valuable)
Carbohydrates
What they do:
- Primary energy for brain and muscles
- Fuel for exercise
- Fiber for gut health
- Spare protein from being used as energy
Types:
| Type | Examples | Speed | When to Use |
|---|---|---|---|
| Simple/fast | Sugar, juice, white bread | Fast absorption | During/after exercise |
| Complex/slow | Oats, rice, sweet potatoes | Slow absorption | Most meals |
| Fiber | Vegetables, whole grains | Indigestible | Every meal |
How much:
- Varies by activity level and preference
- Minimum: ~100g/day for brain function
- Athletes: May need 2-3g/lb bodyweight
Fat
What it does:
- Makes hormones (including testosterone)
- Absorbs fat-soluble vitamins (A, D, E, K)
- Provides essential fatty acids
- Cell membrane structure
- Energy storage
Types:
| Type | Sources | Effect |
|---|---|---|
| Saturated | Meat, dairy, coconut | Neutral to moderate (debated) |
| Monounsaturated | Olive oil, avocado, nuts | Generally healthy |
| Polyunsaturated | Fish, flax, walnuts | Essential, important |
| Trans | Hydrogenated oils | Harmful, avoid |
How much:
- Minimum: 0.3g/lb bodyweight
- Typical: 25-35% of calories
- Don't go too low (hormonal issues)
Micronutrients
Vitamins and minerals needed in smaller amounts.
Key Vitamins
| Vitamin | Key Function | Sources |
|---|---|---|
| A | Vision, immune | Liver, carrots, sweet potato |
| B-complex | Energy metabolism | Meat, eggs, whole grains |
| C | Immune, antioxidant | Citrus, peppers, broccoli |
| D | Bone health, immune | Sunlight, fatty fish, fortified foods |
| E | Antioxidant | Nuts, seeds, olive oil |
| K | Blood clotting, bones | Leafy greens |
Key Minerals
| Mineral | Key Function | Sources |
|---|---|---|
| Calcium | Bones, muscle function | Dairy, leafy greens |
| Iron | Oxygen transport | Red meat, spinach |
| Magnesium | Muscle, nerve, sleep | Nuts, seeds, dark chocolate |
| Zinc | Immune, testosterone | Meat, shellfish, legumes |
| Potassium | Blood pressure, muscle | Potatoes, bananas, meat |
| Sodium | Fluid balance | Salt, processed foods |
The "Eat Real Food" Principle
If you eat a variety of whole foods, you likely get most micronutrients. Supplementation fills gaps.
Water
Often overlooked but critical.
Functions:
- Temperature regulation
- Nutrient transport
- Joint lubrication
- Waste removal
- Cognitive function
How much:
- Baseline: Half your bodyweight in ounces
- Add 16-24 oz for each hour of exercise
- More in heat
Signs of dehydration:
- Dark urine
- Thirst
- Fatigue
- Headache
- Poor performance
Fiber
The underrated nutrient.
Types:
- Soluble: Dissolves in water, feeds gut bacteria (oats, beans)
- Insoluble: Doesn't dissolve, adds bulk (vegetables, whole grains)
Benefits:
- Gut health
- Satiety
- Blood sugar control
- Cholesterol reduction
- Reduced disease risk
Target: 25-35g per day (most people get 15g)
Thermic Effect of Food
Different macros require different energy to digest:
| Macro | Thermic Effect |
|---|---|
| Protein | 20-35% |
| Carbs | 5-10% |
| Fat | 0-3% |
Implication: High-protein diets have a metabolic advantage.
Reading Nutrition Labels
Key lines to check:
- Serving size (often misleading)
- Calories
- Protein
- Fiber
- Added sugars
- Sodium
- Ingredient list (shorter is usually better)
Ingredient list rules:
- Ingredients listed by weight (most to least)
- If you can't pronounce it, be cautious
- Multiple types of sugar = sugar is major component
Practical Guidelines
Build Your Plate
┌─────────────────────────────┐
│ Vegetables │ 1/2 plate
├──────────────┬──────────────┤
│ Protein │ Carbs │ 1/4 plate each
│ │ │
└──────────────┴──────────────┘
+ Healthy fat (cook with or add to meal)
Meal Template
- Protein source (palm-sized portion)
- Vegetables (fist-sized or more)
- Carbohydrate (fist-sized)
- Fat (thumb-sized)
Simple Rules
- Protein at every meal
- Vegetables at every meal
- Drink water before eating
- Eat slowly
- Stop at 80% full
- Minimize liquid calories
- Eat mostly single-ingredient foods
Tracking Food
Why Track (At Least Temporarily)
- Awareness of actual intake
- Identify problem areas
- Ensure adequate protein
- Calibrate portions
- Accountability
How to Track
Apps:
- MyFitnessPal
- Cronometer
- MacroFactor
Tips:
- Weigh food for accuracy (at first)
- Log before or as you eat
- Track consistently (even bad days)
- Be honest
When to Stop Tracking
Once you can intuitively:
- Estimate portions
- Hit protein targets
- Maintain desired weight
Track periodically to recalibrate.