Nutrition Diet: What is the formula for calculating energy consumed?

October 31, 2025 •

4 min read

A person's Total Daily Energy Expenditure (TDEE) can range significantly based on activity level, sometimes accounting for up to 50% of their daily calorie burn. Understanding what is the formula for calculating energy consumed? is crucial for anyone looking to manage their body weight effectively and personalize their nutrition diet plan.

Quick Summary

This guide explains the primary equations used to estimate daily energy consumption, detailing how to calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor formula and then using an activity multiplier to determine Total Daily Energy Expenditure (TDEE).

Key Points

Start with BMR: Before calculating total energy consumed (TDEE), determine your Basal Metabolic Rate (BMR), the energy needed for vital functions at rest.
Mifflin-St Jeor is a Reliable Formula: Use the Mifflin-St Jeor formula for a generally accurate BMR estimate, especially for the average person.
Factor in Activity: Multiply your BMR by an activity multiplier (from 1.2 for sedentary to 1.9 for extra active) to calculate your TDEE.
Recognize Limiting Factors: Understand that BMR formulas are estimates and don't account for all variables, such as body composition, age-related metabolic decline, and individual genetics.
Monitor and Adjust: Use the calculated figures as a guide, but track your actual progress through consistent self-monitoring and adjust your intake based on your body's unique response.
Energy Balance is Key: Whether aiming for weight loss, maintenance, or gain, the fundamental principle is balancing the calories you consume against the calories your body expends.

The Basics of Energy Balance

To achieve any weight-related goal, whether it's maintenance, loss, or gain, understanding the concept of energy balance is fundamental. This balance is a simple equation: 'calories in' versus 'calories out.' The energy you consume through food and drink (calories in) is balanced against the energy your body uses for all its functions (calories out). If 'calories in' equals 'calories out', your weight is maintained. If there is a deficit, you lose weight. If there is a surplus, you gain weight.

Understanding the Components of Energy Expenditure

Your total daily energy expenditure (TDEE) is comprised of three main components:

Basal Metabolic Rate (BMR): This is the energy your body needs to maintain basic, vital functions at complete rest, including breathing, circulation, and cell production. It accounts for the largest portion of your daily energy burn, typically 60-70%.
Thermic Effect of Food (TEF): This is the energy used to digest, absorb, and metabolize the food you eat. TEF accounts for approximately 10% of TDEE and varies slightly based on the macronutrient composition of the meal, with protein requiring more energy to process than carbohydrates or fats.
Activity Energy Expenditure (AEE): This is the energy you burn during any form of physical activity, from structured exercise to daily movements like walking, fidgeting, and even typing. AEE is the most variable component and offers the greatest opportunity for influencing your total energy expenditure.

What is the formula for calculating energy consumed?

To find your Total Daily Energy Expenditure (TDEE), you first need to calculate your Basal Metabolic Rate (BMR). The Mifflin-St Jeor equation is considered one of the most reliable formulas for estimating BMR in the general population.

Mifflin-St Jeor Formulas:

For Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
For Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161

Putting the Mifflin-St Jeor Formula into Practice: Let's calculate the BMR for a 35-year-old female who is 165 cm tall and weighs 70 kg: BMR = (10 x 70) + (6.25 x 165) - (5 x 35) - 161 BMR = 700 + 1031.25 - 175 - 161 BMR = 1395.25 kcal/day

Comparing Different BMR Formulas

While Mifflin-St Jeor is a common choice, other formulas exist, each with its own strengths and limitations.


Formula	Factors Included	Best Suited For	Key Difference
Mifflin-St Jeor	Weight, Height, Age, Gender	General Population	Widely regarded as the most accurate for the average person.
Revised Harris-Benedict	Weight, Height, Age, Gender	General Population	One of the oldest formulas; can sometimes be less accurate than Mifflin-St Jeor.
Katch-McArdle	Lean Body Mass (Weight and Body Fat Percentage)	Athletes, Bodybuilders	Requires an accurate body fat percentage, making it potentially more precise for those with low body fat.

Calculating Total Daily Energy Expenditure (TDEE)

Once your BMR is calculated, you can estimate your TDEE by multiplying your BMR by an activity factor. This factor accounts for your daily physical activity level.

Activity Level Multipliers:

Sedentary: Little to no exercise. BMR x 1.2
Lightly Active: Light exercise or sports 1-3 days/week. BMR x 1.375
Moderately Active: Moderate exercise or sports 3-5 days/week. BMR x 1.55
Very Active: Hard exercise or sports 6-7 days/week. BMR x 1.725
Extra Active: Very hard exercise, physical job, or training twice a day. BMR x 1.9

Continuing the Example: If our 35-year-old female (BMR = 1395.25 kcal/day) is moderately active, her TDEE would be: TDEE = 1395.25 x 1.55 = 2162.64 kcal/day

Beyond the Formulas: Other Factors Influencing Energy Needs

While these formulas provide a reliable estimate, they don't capture the full picture. Several other factors play a significant role in determining your true energy needs:

Body Composition: Muscle mass is more metabolically active than fat mass, meaning it burns more calories at rest. This is why the Katch-McArdle formula, which accounts for body fat, can be more accurate for athletes with high lean mass.
Age: As you age, your metabolism naturally slows down. This is partly due to a decrease in lean body mass, and it means your BMR will gradually decrease over time.
Genetics and Hormones: Individual genetic makeup and hormonal balance can influence metabolic rate. For example, some studies suggest hormonal changes during menopause may impact energy expenditure.
Adaptive Thermogenesis: When you significantly reduce calorie intake, your body may adapt by lowering its metabolic rate more than predicted. This adaptive response is a survival mechanism to conserve energy and can make weight loss more challenging.

Optimizing Your Diet with Calculated Energy Needs

Using the formulas to calculate your estimated energy needs is a powerful first step in building a healthy nutrition diet. It provides a data-driven baseline from which to plan your meals, track your intake, and make informed decisions. For example, if your TDEE for maintenance is 2160 kcal, you know to aim for a lower intake, like 1800 kcal, to create a deficit for weight loss. Conversely, if you want to gain weight, you would aim for a surplus.

While the formulas offer a solid starting point, they should be used as a guide, not a rigid rule. The key to sustainable success is regular self-assessment and adjusting your intake based on your body's actual response. Keeping a food journal, weighing yourself weekly, and observing changes in energy levels and body composition will help you fine-tune your calorie intake to meet your specific goals. The formulas empower you with the initial knowledge, but your body provides the ultimate feedback.

Visit the NIH website for comprehensive information on energy expenditure and nutrition.

Conclusion

Calculating your energy consumption provides a vital framework for any nutrition diet plan. By determining your BMR and using an activity multiplier to estimate your TDEE, you gain the quantitative data needed to pursue weight loss, gain, or maintenance effectively. While formulas like the Mifflin-St Jeor are highly reliable, it is important to remember that they provide estimates. Accounting for individual factors and regularly tracking your progress is key to achieving optimal and sustainable results for your health and fitness goals.

Frequently Asked Questions

To calculate BMR, use the Mifflin-St Jeor formula with your weight (kg), height (cm), and age. For TDEE, multiply your BMR by an activity factor that corresponds to your weekly exercise level (e.g., 1.2 for sedentary, 1.55 for moderately active).

Basal Metabolic Rate (BMR) measures the energy needed for basic bodily functions in a fasting, completely rested state. Resting Metabolic Rate (RMR) includes a slight increase in calories for low-effort daily activities and is typically about 10% higher than BMR.

For the general population, the Mifflin-St Jeor formula is widely considered the most reliable. However, for individuals with a high degree of lean body mass, such as bodybuilders, the Katch-McArdle formula, which accounts for body fat percentage, may be more precise.

Knowing your TDEE is crucial for effective weight management. It provides the daily calorie target needed to maintain your current weight, allowing you to create a calorie deficit for weight loss or a surplus for weight gain.

Diet affects energy expenditure through the Thermic Effect of Food (TEF), which is the energy required for digestion. The macronutrient composition matters, as protein requires more energy to metabolize than carbohydrates or fats.

Wearable devices and activity trackers can provide estimates of your energy expenditure. While they can be useful tools for accountability, they are not always perfectly accurate, so it's important to use them as a guide and not solely rely on their data for precise calculations.

Adaptive thermogenesis is a metabolic slowdown that occurs during calorie restriction. It is a compensatory mechanism where the body lowers its metabolic rate more than expected, which can make weight loss more difficult over time.