Chapter 22: Nutrition System & USDA Integration

This chapter covers Pierre’s nutrition system including daily calorie/macro calculations, USDA food database integration, meal analysis, and nutrient timing for athletes. You’ll learn about energy expenditure estimation, protein requirements, and post-workout nutrition windows.

Daily Nutrition Calculation

Pierre calculates personalized daily nutrition needs based on training load.

Total Daily Energy Expenditure (TDEE):

TDEE = BMR + Activity Calories + Exercise Calories + TEF

Where:
- BMR (Basal Metabolic Rate): Resting energy expenditure
- Activity Calories: Daily lifestyle activity
- Exercise Calories: Planned training
- TEF (Thermic Effect of Food): Digestion cost (~10% of intake)

BMR calculation (Mifflin-St Jeor equation):

Men:   BMR = 10 × weight_kg + 6.25 × height_cm - 5 × age + 5
Women: BMR = 10 × weight_kg + 6.25 × height_cm - 5 × age - 161

Activity multipliers:

• Sedentary: 1.2 (desk job, minimal activity)
• Lightly active: 1.375 (light exercise 1-3 days/week)
• Moderately active: 1.55 (moderate exercise 3-5 days/week)
• Very active: 1.725 (hard exercise 6-7 days/week)
• Extremely active: 1.9 (athlete, 2x/day training)

Exercise calories (from activity data):

Calories = TSS × 1.0 (approximation: 1 TSS ≈ 1 kcal for cycling)

Or use heart rate-based:
Calories = duration_min × (0.6309 × HR + 0.1988 × weight_kg + 0.2017 × age - 55.0969) / 4.184

Macronutrient Targets

Pierre recommends macros based on sport and training phase.

Protein requirements (g/kg body weight/day):

• Endurance athletes: 1.2-1.6 g/kg
• Strength athletes: 1.6-2.2 g/kg
• Ultra-endurance: 1.6-2.0 g/kg
• Recovery day: 1.2-1.4 g/kg

Carbohydrate requirements (g/kg/day):

• Low intensity: 3-5 g/kg
• Moderate training (1hr/day): 5-7 g/kg
• High volume (1-3hr/day): 6-10 g/kg
• Extreme volume (4-5hr/day): 8-12 g/kg

Fat requirements:

• Minimum: 0.8-1.0 g/kg (hormone production, vitamin absorption)
• Typical: 20-35% of total calories
• Low-carb athletes: Up to 60-70% of calories (fat-adapted)

Example calculation (70kg cyclist, moderate training):

TDEE: 2800 kcal
Protein: 70kg × 1.4 g/kg = 98g (392 kcal)
Carbs: 70kg × 6 g/kg = 420g (1680 kcal)
Fat: Remaining = (2800 - 392 - 1680) / 9 = 81g (728 kcal)

Macros: 14% protein / 60% carbs / 26% fat

USDA FoodData Central Integration

Pierre integrates with USDA’s food database for nutrition data.

USDA API endpoints:

• /foods/search: Search food database
• /food/{fdcId}: Get detailed nutrition data
• /foods/list: Browse food categories

Food search (conceptual):

#![allow(unused)]
fn main() {
async fn search_food(query: &str) -> Result<Vec<FoodSearchResult>> {
    let url = format!(
        "https://api.nal.usda.gov/fdc/v1/foods/search?query={}&api_key={}",
        query, api_key
    );

    let response: UsdaSearchResponse = client.get(url).send().await?.json().await?;

    Ok(response.foods.into_iter().map(|food| FoodSearchResult {
        fdc_id: food.fdc_id,
        description: food.description,
        brand_name: food.brand_name,
        serving_size: food.serving_size,
        serving_unit: food.serving_unit,
    }).collect())
}
}

Food nutrition details:

{
  "fdcId": 171705,
  "description": "Banana, raw",
  "foodNutrients": [
    {
      "nutrientName": "Protein",
      "value": 1.09,
      "unitName": "G"
    },
    {
      "nutrientName": "Total lipid (fat)",
      "value": 0.33,
      "unitName": "G"
    },
    {
      "nutrientName": "Carbohydrate, by difference",
      "value": 22.84,
      "unitName": "G"
    },
    {
      "nutrientName": "Energy",
      "value": 89,
      "unitName": "KCAL"
    }
  ]
}

Meal Nutrition Analysis

Pierre analyzes complete meals from multiple foods.

Meal analysis input:

{
  "foods": [
    {"fdc_id": 171705, "servings": 1, "description": "Banana"},
    {"fdc_id": 174608, "servings": 2, "description": "Peanut butter, 2 tbsp"},
    {"fdc_id": 173757, "servings": 2, "description": "Whole wheat bread, 2 slices"}
  ]
}

Meal analysis output:

{
  "total_calories": 450,
  "total_protein_g": 16,
  "total_carbs_g": 58,
  "total_fat_g": 18,
  "macro_percentages": {
    "protein": 14,
    "carbs": 52,
    "fat": 34
  },
  "micronutrients": {
    "vitamin_b6_mg": 0.8,
    "potassium_mg": 850,
    "fiber_g": 10
  }
}

Nutrient Timing

Pierre provides timing recommendations for optimal performance and recovery.

Pre-workout nutrition (1-3 hours before):

• Carbs: 1-4 g/kg body weight (fuel glycogen stores)
• Protein: 0.15-0.25 g/kg (reduce muscle breakdown)
• Fat: Minimal (slows digestion)
• Example: Oatmeal (60g) + banana + protein shake

During workout (>90 minutes):

• Carbs: 30-60 g/hour (maintain blood glucose)
• Electrolytes: Sodium 500-700 mg/L (prevent hyponatremia)
• Fluid: 400-800 ml/hour (depends on sweat rate)

Post-workout nutrition (within 30-60 min):

• Carbs: 1.0-1.2 g/kg (replenish glycogen)
• Protein: 0.25-0.3 g/kg (muscle protein synthesis)
• Ratio: 3:1 to 4:1 carb:protein optimal
• Example (70kg athlete): 70-84g carbs + 18-21g protein

Anabolic window:

• 0-2 hours post-exercise: Glycogen synthesis rate 2-3× higher
• Protein synthesis: Elevated 24-48 hours (not just 30min window)
• Practical: Eat within 2 hours, total daily intake matters most

Cross-Provider Intensity Inference

The get_nutrient_timing tool supports cross-provider activity data to auto-infer workout intensity:

{
  "tool": "get_nutrient_timing",
  "parameters": {
    "weight_kg": 70,
    "daily_protein_g": 140,
    "activity_provider": "strava",
    "days_back": 7
  }
}

How intensity is inferred:

• Fetches recent activities from the specified provider
• Analyzes training volume (hours/day) and heart rate patterns
• Returns intensity_source: "inferred" in the response

Inference thresholds:

Fallback behavior: If activity fetch fails and workout_intensity is also provided, falls back to the explicit value. If neither succeeds, returns an error.

Carbohydrate Periodization

Pierre adjusts carb intake based on training intensity.

Daily carb adjustment:

Rest day:       3-4 g/kg (maintenance)
Easy day:       4-5 g/kg (light recovery)
Moderate day:   5-7 g/kg (typical training)
Hard day:       7-9 g/kg (high intensity)
Race day:       8-12 g/kg (maximum fueling)

Benefits of periodization:

1. Metabolic flexibility: Trains fat oxidation on low-carb days
2. Glycogen supercompensation: Maximizes storage for key workouts
3. Body composition: Reduces excess carbs on easy days
4. Performance: Fuels hard sessions adequately

Example week (70kg cyclist):

Monday (rest):      70kg × 3g = 210g carbs
Tuesday (easy):     70kg × 5g = 350g carbs
Wednesday (hard):   70kg × 8g = 560g carbs
Thursday (moderate): 70kg × 6g = 420g carbs
Friday (easy):      70kg × 5g = 350g carbs
Saturday (long):    70kg × 9g = 630g carbs
Sunday (race):      70kg × 10g = 700g carbs

Hydration Recommendations

Pierre calculates sweat rate and hydration needs.

Sweat rate calculation:

Sweat Rate (L/hr) = (Pre-Weight - Post-Weight + Fluid Consumed - Urine Output) / Duration

Example:
Pre: 70.0 kg
Post: 69.2 kg
Fluid: 0.5 L
Duration: 1 hour
Sweat Rate = (70.0 - 69.2 + 0.5 - 0) / 1 = 1.3 L/hr

Hydration guidelines:

• Daily baseline: 30-35 ml/kg body weight
• Pre-exercise: 5-7 ml/kg 2-4 hours before
• During exercise: Replace 60-80% of sweat losses
• Post-exercise: 150% of fluid deficit (1.5L for each kg lost)

Electrolyte needs (sodium):

• Low sweaters: 300-500 mg/L
• Average: 500-800 mg/L
• Heavy/salty sweaters: 800-1200 mg/L

Recipe Management (Combat des Chefs)

Pierre provides training-aware recipe management using the “Combat des Chefs” architecture:

• LLM clients generate recipes (cost-efficient, creative)
• Pierre validates nutrition via USDA (accurate, authoritative)
• Per-user storage (private recipe collections)

Meal Timing & Macro Targets

Recipes are categorized by training timing with specific macro distributions:

Recipe Workflow

Step 1: Get Constraints

{
  "tool": "get_recipe_constraints",
  "parameters": {
    "meal_timing": "post_training",
    "target_calories": 600
  }
}

Returns macro targets, guidelines, and example ingredients for the LLM to use.

Step 2: LLM Generates Recipe

The AI assistant creates a recipe based on constraints and user preferences.

Step 3: Validate with Pierre

{
  "tool": "validate_recipe",
  "parameters": {
    "name": "Recovery Protein Bowl",
    "meal_timing": "post_training",
    "target_calories": 600,
    "ingredients": [
      {"name": "chicken breast", "quantity": 200, "unit": "grams"},
      {"name": "brown rice", "quantity": 1, "unit": "cup"},
      {"name": "broccoli", "quantity": 150, "unit": "grams"}
    ]
  }
}

Pierre validates nutrition via USDA and returns:

• Actual calories and macros
• Compliance score vs targets
• Suggestions for improvements

Step 4: Save if Valid

{
  "tool": "save_recipe",
  "parameters": {
    "name": "Recovery Protein Bowl",
    "meal_timing": "post_training",
    "ingredients": [...],
    "instructions": ["Cook rice", "Grill chicken", "Steam broccoli", "Combine and serve"],
    "tags": ["high-protein", "post-workout", "quick"]
  }
}

Unit Conversion

Pierre automatically converts common units to grams for accurate nutrition lookup:

Recipe Tools Summary

Key Takeaways

1. TDEE calculation: BMR + activity + exercise + TEF determines daily calorie needs.

2. Protein: 1.2-2.2 g/kg depending on sport and training phase.

3. Carbs: 3-12 g/kg based on training volume and intensity.

4. USDA integration: 800,000+ foods with detailed nutrition data via FoodData Central API.

5. Meal analysis: Sum nutrition from multiple foods for complete meal breakdown.

6. Nutrient timing: Pre (1-3hr), during (>90min), post (30-60min) windows optimize performance.

7. Carb periodization: Match carb intake to training intensity for metabolic flexibility.

8. Sweat rate: Measure weight before/after to calculate individual fluid needs.

9. Post-workout ratio: 3:1 to 4:1 carb:protein ratio optimizes recovery.

10. Total daily intake: 24-hour totals matter more than strict timing windows.

11. Combat des Chefs: LLM generates recipes, Pierre validates via USDA for accuracy.

12. Meal timing macros: Pre-training (high carb), post-training (high protein), rest day (balanced).

Detailed Methodology Reference

For comprehensive technical documentation of all nutrition algorithms and USDA integration, see the Nutrition Methodology Document in the Pierre source repository:

docs/nutrition-methodology.md

This detailed reference document covers:

For implementers: The methodology document includes complete formulas, USDA API examples, and validation rules for every nutrition tool in Pierre.

End of Part VI: Tools & Intelligence

You’ve completed the tools and intelligence section. You now understand:

• All 47 MCP tools and their usage (Chapter 19)
• Sports science algorithms (Chapter 20)
• Recovery and sleep analysis (Chapter 21)
• Nutrition system, USDA integration, and recipe management (Chapter 22)

Next Chapter: Chapter 23: Testing Framework - Begin Part VII by learning about Pierre’s testing infrastructure including synthetic data generation, E2E tests, tools-to-types validation, and test organization.