Protein Intake Calculator

def protein_needs(weight_kg, activity_level, goal):
    """
    Calculate daily protein needs (g/day).

    activity_level: "sedentary" | "light" | "moderate" | "heavy" | "athlete"
    goal: "maintain" | "lose_fat" | "build_muscle"
    """
    # Base multiplier per kg of body weight
    base = {
        "sedentary":  0.8,
        "light":      1.2,
        "moderate":   1.4,
        "heavy":      1.6,
        "athlete":    1.8,
    }
    multiplier = base.get(activity_level, 1.2)

    # Adjust for goal
    if goal == "build_muscle":
        multiplier = max(multiplier, 1.6)
        multiplier = min(multiplier + 0.4, 2.2)
    elif goal == "lose_fat":
        multiplier = max(multiplier + 0.4, 1.8)  # preserve lean mass

    return weight_kg * multiplier


def lean_body_mass_based(weight_kg, body_fat_pct, goal):
    """Calculate protein from lean body mass for high body-fat individuals."""
    lbm = weight_kg * (1 - body_fat_pct / 100)
    multiplier = 1.8 if goal == "build_muscle" else (2.0 if goal == "lose_fat" else 1.6)
    return lbm * multiplier


# Example usage
print("=== Total body weight method ===")
for activity in ["sedentary", "light", "moderate", "heavy", "athlete"]:
    g = protein_needs(75, activity, "build_muscle")
    print(f"  {activity:10}: {g:.0f} g/day")

print("\n=== LBM method (75 kg, 20% body fat) ===")
for goal in ["maintain", "build_muscle", "lose_fat"]:
    g = lean_body_mass_based(75, 20, goal)
    print(f"  {goal:15}: {g:.0f} g/day")