Calculating Energy Needs & Macros for Patients
Registered Dietitians at Nourish are empowered to calculate and personalize energy and macronutrient needs for patients using validated methods. This guide provides a quick reference to help you estimate calorie needs and protein targets based on clinical best practices.
Inputs You'll Need
Before starting your calculation, gather the following:
Age
Sex
Height (inches or cm)
Weight (lbs or kg)
BMI (auto-calculate if not provided)
Activity level
Step 1: Estimate Energy Needs (Calories)
Use the Mifflin-St Jeor equation with actual body weight (ABW):
Men:
10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) + 5Women:
10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) – 161
You can use these resources to get accurate numbers quickly. The first is recommended, but others offer alternative calculation methods.
Multiply by Activity Factor:
Activity Level | Multiplier |
|---|---|
Sedentary | 1.2 |
Lightly active | 1.375 |
Moderately active | 1.55 |
Very active | 1.725 |
Extra active | 1.9 |
Adjust Estimated Caloric Needs (if relevant):
Consider modifying estimated energy needs based on the individual’s clinical context, health goals, and preferences. This may include adjusting for changes in weight, metabolic conditions, or other relevant factors. Use clinical judgment to determine whether an increase or decrease in caloric intake is appropriate.
Finalize Calculation:
Once you’ve calculated Total Daily Energy Expenditure (TDEE), determine the appropriate calorie goal based on the patient’s health status and goals:
TDEE ± Adjustment = Calorie Goal
Round the final calorie goal to the nearest 50 or 100 kcal to support practical implementation and meal planning.
Step 2: Select the Right Weight for Protein Calculations
Protein needs are based on metabolically active tissue, which is primarily lean body mass -not total body weight. For patients with overweight or obesity, using actual body weight can overestimate protein requirements because excess adipose tissue does not increase protein needs proportionally.
To account for this, use the following guidelines based on BMI:
BMI Range | Weight to Use for Protein Needs | Why This Matters |
|---|---|---|
< 30 | Actual Body Weight (ABW) | Most weight is likely to be lean or moderately proportioned fat mass |
30-40 | Ideal Body Weight (IBW) | Avoids inflating protein targets due to excess adiposity |
> 40 | Adjusted Body Weight (AdjBW) | Balances ABW and IBW to reflect higher lean mass without overestimating needs |
IBW Formula:
Men:
50 kg + 2.3 × (height in inches - 60)Women:
45.5 kg + 2.3 × (height in inches – 60)
AdjBW Formula (BMI > 40 only):
AdjBW = IBW + 0.4 × (ABW – IBW)
This approach is standard in clinical nutrition to ensure adequate but not excessive protein intake, particularly for patients who may be at risk for renal strain, GI side effects, or poor adherence with unnecessarily high protein goals.
You can use this resource to get accurate IBW/AdjBW values: MDCalc IBW/AdjBW calculator
Step 3: Calculate Protein Needs
Multiply the selected weight (ABW, IBW, or AdjBW) by a range of 1.2-1.6 g/kg/day:
Use the lower end (1.2 g/kg) for less active or older patients
Use the higher end (1.6 g/kg) for active individuals or those with higher needs
Clinical Notes
Always pair estimates with clinical judgment - adjust for patient preferences, condition-specific needs, and specific health and nutrition goals discussed in session.
For disordered eating or eating disorder populations, avoid rigid calorie and macro goals and use a more flexible, weight-neutral approach.