Calculation Settings

This page explains how BMR formulas, body fat algorithms, daily energy adjustments, and calorie deficit targets are calculated in SparkyFitness.

1. Basal Metabolic Rate (BMR) Algorithms

Your Basal Metabolic Rate (BMR) represents the energy your body requires to perform basic life-sustaining functions at rest. SparkyFitness supports multiple clinical formulas to estimate BMR:

Note: Weight ($W$) is in kg, Height ($H$) is in cm, and Age ($A$) is in years.

2. Body Fat Algorithms

Body Fat Percentage is used directly in lean-mass BMR formulas (Katch-McArdle/Cunningham). SparkyFitness can estimate body fat percentage from your measurements using two algorithms:

U.S. Navy Method

Uses circumferences to estimate body fat. Measurements are converted to inches for the standard formula:

• Males: $86.01 \times \log_{10}(\text{waist} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76$
• Females: $163.205 \times \log_{10}(\text{waist} + \text{hips} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387$

BMI Method

Uses height, weight, and age to estimate body fat:

• Males: $1.2 \times \text{BMI} + 0.23 \times \text{Age} - 16.2$
• Females: $1.2 \times \text{BMI} + 0.23 \times \text{Age} - 5.4$
• (where $\text{BMI} = \text{Weight (kg)} / \text{Height (m)}^2$)

3. Daily Calorie Goal Adjustment

This setting determines how physical activity changes your calorie budget throughout the day:

• Adaptive TDEE: Dynamically computes your metabolic expenditure by correlating your actual weight changes with your historical calorie intake over the last 35 days. (Best for high-precision tracking).
  • Expenditure (Adaptive TDEE): On the Diary page, "Expenditure" represents your calculated Total Daily Energy Expenditure (TDEE). This is the baseline number from which your deficit/surplus is subtracted.
  • Fallback Behavior: If you have insufficient history (less than 14 days of weight and calorie data, or fewer than 7 days of calorie entries $\ge 200\text{ kcal}$), the system will use a fallback estimate based on the standard BMR × Activity Multiplier formula until enough data is collected.
• Dynamic Goal: Increases your budget as you burn active calories or take steps (adds exercise directly back to your budget).
• Fixed Goal: Your calorie target remains completely static, ignoring daily exercise.
• Percentage Earn-Back: Adds back a custom percentage (e.g., $50%$) of active calories burned to create a buffer against device calorie over-estimations.
• Device Projection: Projects your total full-day burn by extrapolating active steps and device data to midnight (MyFitnessPal style).

4. Goal Mode & Caloric Deficits

Goal Mode applies a body composition percentage-based deficit or maintenance target to your baseline maintenance:

Calculation Methods

• Adaptive Method: Applies the deficit to your Calculated Adaptive TDEE (falling back to BMR × activity multiplier if history is insufficient).
• Manual Method: Applies the deficit to your manually entered calorie target.

5. Metabolic Safety Floors

To protect long-term metabolic health and avoid muscle wasting, SparkyFitness checks all calorie goals against safety limits:

1. Resting Metabolism (RMR) Floor: Your target should not fall below your resting metabolic rate.
2. Absolute Clinical Floor: $1,200$ kcal for biological females; $1,500$ kcal for biological males.

!IMPORTANTEnforcement Behavior:

• Under the Adaptive method, if your calculated target falls below the safety floor, the system automatically raises your target to the effective floor.
• Under the Manual method, the target is not automatically raised, but a prominent warning banner is displayed warning you that your budget is in an unsafe range.