How Foodzilla Calculates Your Client’s Daily Calorie and Macronutrient Needs
Foodzilla can automatically calculate a client’s daily energy and macronutrient targets using their body measurements, activity level, selected BMR formula, and health goals.
These calculations can be reviewed and adjusted at any time, giving you full control over the nutrition targets used for each client.
1. Add the Client’s Body Measurements
Foodzilla uses the client’s body information to calculate their nutrition goals. Enter:
• Gender
• Age
• Height
• Weight
• Body fat percentage, when available
• Physical Activity Level
Body fat percentage is particularly useful when using formulas based on lean body mass.
2. Select a Physical Activity Level
Physical Activity Level, or PAL, represents the client’s overall daily activity, not just their workouts.
Foodzilla includes the following activity levels:
| Activity Level | PAL Factor | Description |
|---|---|---|
| Sedentary | 1.2 | Seated nearly all day |
| Light | 1.53 | Mostly seated, with some walking |
| Moderate | 1.76 | On their feet much of the day, or a desk job plus regular training |
| Very active | 2.25 | Physically demanding days or hard daily training |
| Extra active | 2.5 | Heavy physical work and training together |
The estimated total daily energy requirement is calculated as:
Total Energy = BMR × PAL
*Custom PAL
You can also enter a Custom PAL between 1.0 and 3.0.
This overrides the selected activity band and is useful when a client falls between two categories. For example, someone with a desk job who trains heavily may require a PAL between Moderate and Very Active.
Leave this field blank to use the standard activity level selected above.
3. Choose a BMR Formula
Under Nutrition Goals, you can select the formula Foodzilla uses to calculate Basal Metabolic Rate.
Available options include:
• Automatic (recommended)
• Mifflin St Jeor
• Original Harris Benedict (1919)
• Revised Harris Benedict (1984)
• Katch McArdle
• Cunningham
• Custom
Automatic Formula
Automatic is the recommended option.
Foodzilla uses a lean body mass based calculation when the client’s body fat percentage is available. If body fat is not available, it automatically falls back to the Mifflin St Jeor formula.
Mifflin St Jeor
Mifflin St Jeor calculates BMR using the client’s:
• Weight
• Height
• Age
• Gender
It can therefore be used without body fat information.
Harris Benedict
Foodzilla also supports both the Original Harris Benedict (1919) and Revised Harris Benedict (1984) formulas if you prefer to use one of these methods.
Katch McArdle and Cunningham
These formulas use lean body mass and therefore require the client’s body fat percentage.
If body fat information is missing, Foodzilla will display a warning and use Mifflin St Jeor instead until body fat is entered.
Custom BMR
If you have calculated your client’s BMR separately, select Custom and enter your own BMR value.
This gives you complete control over the starting energy calculation.
Reviewing the Calculation
Within the client’s Nutrition Goals section, you can expand Understanding Your Client’s Nutrition Calculations to see how Foodzilla arrived at the recommendation.
This includes the selected BMR calculation, PAL factor, health goal adjustment, and macronutrient ratios, making it easier to review and modify your client’s targets when needed.
What is the Harris-Benedict Equation?
The Harris-Benedict equation is a widely used formula that estimates an individual's Basal Metabolic Rate (BMR) and then adjusts it for physical activity levels to calculate daily calorie needs.
✅ Step 1: Calculate Basal Metabolic Rate (BMR)
We use the Harris-Benedict Equation to estimate the calories the body needs at rest.
- For Men:
- BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- For Women:
- BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
The BMR is then multiplied by an activity factor to determine the total daily calorie requirement.
✅ Step 2: Apply Physical Activity Level (PAL)
We multiply the BMR by the client’s activity level to estimate how much energy they burn daily.
| Activity Level | PAL Factor | Description |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise |
| Light | 1.53 | Light exercise 1–3 days/week |
| Moderate | 1.76 | Moderate exercise 3–5 days/week |
| Very active | 2.25 | Hard exercise 6–7 days/week |
| Extra active | 2.5 | Very hard training or physically demanding job |
✅ Step 3: Adjust for Health Goal
Then we adjust calories based on the goal selected:
| Goal | Adjustment |
|---|---|
| Weight loss | −500 kcal/day |
| Weight gain | +500 kcal/day |
| Maintenance | No adjustment |
These adjustments help clients reach their targets effectively and safely.
✅ Step 4: Assign Macronutrient Ratios
Macros are set based on the selected goal:
| Goal | Fat | Protein | Carbs |
|---|---|---|---|
| Weight loss | 30% | 30% | 40% |
| Strength gain | 20% | 35% | 45% |
| Maintenance | 25% | 35% | 40% |
Macro gram conversions
Fat (g) = (calories × fat%) ÷ 9
Protein (g) = (calories × protein%) ÷ 4
Carbs (g) = (calories × carbs%) ÷ 4
🔁 kcal vs kJ Conversion
Foodzilla supports both calorie units.
1 kcal = 4.184 kJ
We automatically convert based on your preference in settings.
If you would like us to use a different formula for your clients, please contact us. For any further assistance or questions, feel free to reach out through the green chat bubble. 🦄