The Foundational Step: Calculating Your Basal Metabolic Rate (BMR)
MyFitnessPal's process begins by establishing your Basal Metabolic Rate (BMR), which represents the number of calories your body needs to perform its most basic functions at rest. The app uses the Mifflin-St Jeor equation, a widely accepted method for estimating BMR, using your age, gender, height, and weight.
How the BMR calculation works
The Mifflin-St Jeor equation takes your personal data and applies a gender-specific formula. This initial BMR is the baseline energy expenditure before considering activity or goals.
Adjusting for Activity Level: From BMR to TDEE
To account for your daily energy expenditure beyond rest, MyFitnessPal asks you to select an activity level that describes your typical routine outside of exercise. This selection multiplies your BMR to determine your Total Daily Energy Expenditure (TDEE). Activity level options typically range from Sedentary (mostly sitting) to Very Active (heavy physical activity). Selecting the appropriate level is crucial for an accurate starting calorie goal.
Modifying Goals for Weight Loss, Gain, or Maintenance
MyFitnessPal adjusts your TDEE based on your weight goal. You specify how much weight you aim to lose or gain per week, usually between 0.5 to 2 pounds.
The weekly weight change formula
Based on the principle that 3,500 calories roughly equals one pound of body fat, MyFitnessPal creates a calorie deficit or surplus. To lose one pound per week, it subtracts about 500 calories daily from your TDEE. To gain one pound, it adds about 500 calories. For maintenance, the goal matches your TDEE. The app promotes healthy changes by limiting weekly loss to two pounds and recommending minimum daily calorie intakes (e.g., 1,500 for men, 1,200 for women).
The Role of Exercise in Your Daily Calorie Budget
MyFitnessPal's initial goal already incorporates the calorie adjustment for your weight target before considering exercise. Logging a workout adds burned calories back to your daily allowance.
Example:
- Daily goal for weight loss: 1,800 calories.
- Logged workout: 300 calories burned.
- New daily budget: 2,100 calories (1,800 + 300).
This is known as 'Net Calories'. While helpful, be aware that fitness trackers can overestimate calorie burn. Some users prefer not to consume all exercise calories back.
The Calculation Process in a Nutshell
| Step | Description | MyFitnessPal Action | User Input | Key Concept |
|---|---|---|---|---|
| 1. Initial Setup | Collects basic user data. | Asks for height, weight, age, and sex. | Height, weight, age, sex. | Establish BMR base. |
| 2. BMR Calculation | Estimates calories burned at rest. | Uses the Mifflin-St Jeor formula. | Internal calculation. | Basal Metabolic Rate. |
| 3. TDEE Adjustment | Accounts for non-exercise activity. | Multiplies BMR by an activity level factor. | Sedentary, Lightly Active, Active, Very Active. | Total Daily Energy Expenditure. |
| 4. Goal Modification | Creates calorie surplus or deficit. | Adds or subtracts calories based on weekly goal. | Weekly weight loss/gain rate. | Caloric deficit/surplus. |
| 5. Exercise Inclusion | Adjusts daily budget for logged workouts. | Adds back calories burned from exercise. | Manual or auto-synced exercise log. | Net Calories. |
How Your Calorie Goal Changes Over Time
MyFitnessPal continuously recalibrates your calorie goals as you log your weight, typically weekly. This accounts for changes in your body composition, ensuring your goals remain accurate and support ongoing progress.
How MyFitnessPal compares to other methods
MyFitnessPal combines established science, like the Mifflin-St Jeor equation, with user data for a personalized approach. While other methods exist, including more precise metabolic testing or apps focusing heavily on macronutrients, MyFitnessPal's strength lies in its accessibility and dynamic adjustments based on user input. Premium offers more detailed tracking options.
Conclusion
MyFitnessPal sets your calorie goal by using a science-based BMR estimate, adjusting for your activity level, and then modifying the total based on your weight goals. The Net Calories system, which adds back exercise calories, provides flexibility, though users should be mindful of potential overestimation by trackers. The app's dynamic adjustments based on your weight changes make it an effective tool for long-term health management. Understanding this process helps you utilize the app more effectively to achieve your fitness targets.
