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.

Measured BMR

If a smart scale or a connected health app reports a BMR, SparkyFitness can use that measured value for that day instead of the formula above, and the calculation breakdown on the Diary labels it Measured.

This is off by default. Turn on Use measured BMR from check-ins and synced devices in Calculation Settings to enable it; until you do, your chosen formula is always used.

• It counts only on the day it was recorded. A measured BMR is never carried forward. Days without a reading fall back to your chosen formula, so turning the sync off restores the formula the next day — you do not have to delete anything.
• Implausible readings are ignored. A value must fall between 600 and 6,000 kcal. When your profile is complete enough to produce a formula estimate, it must also land within 60–160% of that estimate; if it is not — for example when height or date of birth is missing — the absolute bounds decide on their own. A partial-day figure or a mis-mapped metric is discarded and the formula is used instead. The second check matters because a value can look reasonable on its own and still be impossible for your body.
• Readings for a day that has not finished are refused. Some providers report BMR as a running daily total rather than a rate, so a sync partway through the day hands back part of the day's figure. Only completed days are accepted.
• It also sets your safety floor. The Standard Adaptive Safety Floor uses the higher of your RMR and the clinical minimum, and your measured BMR is that RMR when one is available. So a measured value that differs from the formula moves the floor under your calorie goal, not just the estimate above it.

To stop using measured values, turn the setting off in Calculation Settings. That covers every source at once. You can also disable BMR sync at the provider — on Apple Health and Health Connect that is a per-metric setting, so you can keep syncing weight and body fat while dropping BMR. Garmin has no per-metric control, which is why the Calculation Settings toggle exists.

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 × log10(waist - neck) - 70.041 × log10(height) + 36.76
• Females: 163.205 × log10(waist + hips - neck) - 97.684 × log10(height) - 78.387

BMI Method

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

• Males: 1.2 × BMI + 0.23 × Age - 16.2
• Females: 1.2 × BMI + 0.23 × Age - 5.4
• (where BMI = Weight (kg) / 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 28 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 ≥ 200 kcal), the system will use a fallback estimate based on the standard BMR × Activity Multiplier formula until enough data is collected.
  • The formula: TDEE = Average Daily Calories - (Daily Weight Change in kg × 6,000 kcal/kg). The average covers only days with at least 200 kcal logged — unlogged days are skipped, not counted as zero — while the weight change spans the whole 28-day window.
  • Plausibility cap: the result is capped to within ±500 kcal of BMR × Activity Multiplier. Your Activity Level therefore keeps mattering after Adaptive goes live: it does not feed the estimate, but it sets the window the estimate is allowed to land in. A level set well below your real activity can hold a genuinely higher measured expenditure down, and the Diary's calculation breakdown says so when the cap binds.
    The 6,000 kcal/kg term is an energy density — how many calories a kilogram of body weight represents — which is what lets a weight trend be converted into calories. If you ate 2,000 kcal/day and lost 0.5 kg over 14 days, that lost weight represents about 3,000 kcal your body burned beyond what you ate, or ~214 kcal/day, so your true expenditure was ~2,214 kcal/day.
    Weight lost or gained is never pure fat. Fat carries ~9,441 kcal/kg and lean tissue and water only ~1,816 kcal/kg; 6,000 reflects a typical blend of roughly 55% fat to 45% lean and water. This is a modelling constant and is not user-configurable — it is not something you can observe about yourself without a body composition scan, and a wrong value would skew every calorie target with no visible symptom.
• 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: Uses the cumulative Total Calories value synced from Health Connect (resting plus active energy). For the current day, it projects that value from its dedicated source capture time to midnight and treats the result as your live TDEE; completed days use the recorded total without extrapolation. Goal Mode is then applied directly: for example, a projected TDEE of 2,400 kcal becomes 2,400 kcal at Maintain, 2,160 kcal at Body Recomposition (-10%), or 2,640 kcal at Lean Bulk (+10%). Enable Total Calories in the Android Health Connect sync settings. When that value is unavailable, too early, or implausible for a complete daily total, SparkyFitness falls back to BMR plus projected active calories.

!NOTE If you use Nutrient Goal Direction's Target range for calories, note that Adaptive, Dynamic, Percentage Earn-Back, and Device Projection all recalculate your calorie goal value regularly — a manually entered target band won't move with it. Target range for calories works best paired with Fixed Goal.

4. Goal Mode & Caloric Deficits

Goal Mode applies a body composition percentage-based adjustment to your baseline maintenance. The sign works the way you would expect: positive adds calories, negative cuts them.

Rate of Change Guidance

The app rates your projected rate of change, and the safe range is not symmetric:

• Weight loss: up to ~1.0% of body weight per week is comfortable; above 1.5% is flagged as excessive.
• Weight gain: up to ~0.25% per week is comfortable; above 0.5% is flagged, because past that point the extra weight is predominantly fat rather than muscle.

Gain is deliberately much slower than loss. Muscle growth is limited by training and recovery, not by how large the surplus is.

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.

Device Projection always uses the projected device TDEE as the live baseline for the selected Goal Mode; the calculation-method selector controls the saved non-device baseline and previews used by the other modes.

5. Metabolic Safety Floors

SparkyFitness shows two recommended safety limits for calorie goals:

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.

!IMPORTANTAdaptive Safety Floor:

• Standard (default): The higher of your estimated RMR and the sex-specific clinical minimum is enforced. If an Adaptive target falls below it, SparkyFitness raises the target and explains which limit bound.
• Custom minimum: Replaces the Standard floor with a calorie value you choose. This can be below or above the recommended limits; those recommendations and health warnings remain visible.
• Disabled: Does not automatically raise Adaptive targets. The calculated target is used as-is, while recommended limits and health warnings remain visible.
• 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.

Under the Adaptive method the floor applies whenever the calculated target falls below it. That is almost always a deficit, but a surplus can trip it too: if your entire maintenance sits below the clinical minimum, even a gain goal is raised to that minimum.

!TIP If a goal mode appears to have no effect, the Standard floor is binding. That is usually about your activity level, not your body size. With the fallback estimate (TDEE = RMR × activity multiplier) and RMR as the binding half, the floor bites once your deficit exceeds roughly 1 - 1/activityMultiplier — about 17% at Sedentary (×1.2), and 0% at None (×1.0), where every deficit mode returns the same target. Once Adaptive has enough history it uses your measured TDEE, so the real limit is how far your expenditure sits above your RMR. A sedentary man and a sedentary woman of very different sizes hit the same ceiling.

If you are still on the fallback estimate, check your Activity Level and profile data first, since they set the ceiling there and are the most common things to have understated. Once Adaptive is using measured TDEE the setting no longer feeds the estimate itself, and the ceiling reflects your real expenditure — but it still sets the ±500 kcal plausibility cap around BMR × Activity Multiplier, so an understated level can still hold your measured TDEE down. If your target has been agreed with a qualified clinician and still falls below the Standard floor, choose a Custom minimum or Disabled. Very small adults may find the clinical minimum sits above their own maintenance, in which case those two options are the only way to set a deficit at all. Very low calorie targets can carry health risks and may require medical supervision.

6. Nutrient Calculation Algorithms

These pickers choose a formula for suggesting gram targets for certain nutrient goals, based on your calorie goal, age, and sex:

• Fat Breakdown Algorithm (AHA Guidelines / Keto-Adapted / Mediterranean): suggests how to split total fat into saturated, polyunsaturated, monounsaturated, and trans fat.
• Mineral Calculation Algorithm (RDA Standard / Athletic Performance / Heart Health): suggests sodium, potassium, calcium, and iron targets.
• Vitamin Calculation Algorithm (RDA Standard / Immune Support / Antioxidant Focus): suggests Vitamin A and C targets.
• Sugar Calculation Algorithm (WHO Guidelines 10% max / Low-Carb-Keto 5% max / Balanced 15% max): suggests a target for the built-in Total Sugar goal, as a percentage of your daily calories.

This is different from the Added Sugars auto-calculate control described in Goals → Tracking Added Sugars — that one computes a limit for a separate, user-created "Added Sugars" custom nutrient using WHO/AHA guidelines, not this Total Sugar percentage.