Diet Plan Calculator

Data Source & Methodology

This calculator estimates your daily calorie needs using the **Mifflin-St Jeor equation**. This equation, published in 1990, is widely considered by organizations like the Academy of Nutrition and Dietetics to be the most reliable formula for calculating Basal Metabolic Rate (BMR) in healthy adults, superseding the older Harris-Benedict formula.

• Authoritative Source: Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. *The American journal of clinical nutrition*, 51(2), 241-247.
• Reference Link: https://doi.org/10.1093/ajcn/51.2.241

All calculations are based strictly on the formulas from this source, combined with standard physical activity level (PAL) multipliers to estimate Total Daily Energy Expenditure (TDEE).

The Formulas Explained

The calculation is a two-step process. First, we determine your Basal Metabolic Rate (BMR). Second, we multiply your BMR by an activity factor to find your Total Daily Energy Expenditure (TDEE).

1. Basal Metabolic Rate (BMR)

BMR is the energy your body uses at rest just to stay alive (e.g., breathing, circulation).

2. Total Daily Energy Expenditure (TDEE)

TDEE is your BMR multiplied by your activity level. This is the total number of calories you burn in a day, and it's the amount you should eat to maintain your current weight.

3. Goal Calories

To determine your target calories for weight loss or gain, we create a calorie deficit or surplus. A deficit of 500 calories per day typically results in a loss of 0.5 kg (1 lb) per week.

Glossary of Variables

Age

Your age in years. BMR tends to decrease as you get older.

Gender

Used to select the correct BMR formula. Men typically have higher muscle mass and thus a higher BMR.

Height & Weight

Your physical size. Larger bodies require more energy to maintain.

Activity Multiplier

A factor that accounts for all your daily movement:

• Sedentary (1.2): Office job, little to no formal exercise.
• Lightly Active (1.375): Light exercise (e.g., walking) 1-3 days/week.
• Moderately Active (1.55): Moderate exercise (e.g., gym) 3-5 days/week.
• Very Active (1.725): Hard exercise 6-7 days/week.
• Extra Active (1.9): Hard daily exercise and/or a physical job.

Basal Metabolic Rate (BMR)

The calories your body burns at complete rest (e.g., if you stayed in bed all day).

Total Daily Energy Expenditure (TDEE)

Your BMR plus the calories burned from all activity. This is your "maintenance" calorie level.

How It Works: A Step-by-Step Example

Let's calculate the needs for a **35-year-old female** who is **165 cm** tall, weighs **70 kg**, is **moderately active**, and wants to achieve **mild weight loss** (-250 calories).

1. Calculate BMR (Female formula):
   $$BMR = (10 \times 70) + (6.25 \times 165) - (5 \times 35) - 161$$ $$BMR = 700 + 1031.25 - 175 - 161$$ $$BMR = 1395 \text{ calories/day}$$
2. Calculate TDEE (Maintenance Calories):
   $$TDEE = BMR \times \text{Activity Multiplier}$$ $$TDEE = 1395 \times 1.55 \text{ (Moderately Active)}$$ $$TDEE = 2162 \text{ calories/day}$$
3. Calculate Goal Calories (Mild Weight Loss):
   $$\text{Goal Calories} = TDEE + \text{Goal Modifier}$$ $$\text{Goal Calories} = 2162 + (-250)$$ $$\text{Goal Calories} = 1912 \text{ calories/day}$$

To achieve mild weight loss, this individual should aim for approximately **1,912 calories per day**.

Frequently Asked Questions (FAQ)