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The Mifflin-St. Jeor Equation: A Powerful Tool for Nutrition Professionals

Mifflin-St. Jeor Equation

Welcome to our comprehensive guide on Mifflin-St. Jeor is a widely used equation in the field of nutrition. As nutrition professionals, it is crucial to have a deep understanding of various methodologies and tools that assist in calculating energy expenditure and determining caloric needs accurately. In this article, we will delve into the Mifflin-St. Jeor equation, its history, application, and why it is an invaluable tool for nutrition professionals. So, let's dive in!

Understanding the Mifflin-St. Jeor Equation

The Origins

The Mifflin-St. Jeor equation, developed by Mifflin and St. Jeor in 1990, is a widely recognized and validated method for estimating resting metabolic rate (RMR). RMR refers to the number of calories an individual requires at rest to maintain basic bodily functions such as breathing, circulation, and cellular processes.

The Equation

The Mifflin-St. Jeor equation, expressed in calories per day, takes into account the individual's age, weight, height, and gender. Here is the equation:

For men: RMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) + 5

For women: RMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) - 161

Advantages and Validity

The Mifflin-St. Jeor equation has gained popularity due to its accuracy and applicability to a wide range of individuals, including those who are overweight or obese. Research studies have shown that it outperforms other commonly used equations, such as the Harris-Benedict equation, in estimating RMR.

Application in Clinical Practice

Determining Total Energy Expenditure (TEE)

While the Mifflin-St. Jeor equation estimates RMR, it is important to consider an individual's activity level to determine their total energy expenditure (TEE). TEE includes the calories burned through physical activity and exercise. To calculate TEE, we multiply the estimated RMR by an activity factor, which varies based on the individual's lifestyle:

  • Sedentary (little to no exercise): RMR * 1.2

  • Lightly active (light exercise/sports 1-3 days/week): RMR * 1.375

  • Moderately active (moderate exercise/sports 3-5 days/week): RMR * 1.55

  • Very active (hard exercise/sports 6-7 days/week): RMR * 1.725

  • Super active (very hard exercise/sports & physical job or 2x training): RMR * 1.9

Tailoring Caloric Needs

The Mifflin-St. Jeor equation, along with consideration of an individual's activity level, plays a vital role in tailoring their caloric needs. By adding the calories required for physical activity to the estimated RMR, nutrition professionals can determine the appropriate caloric intake for weight maintenance, weight loss, or weight gain.

Customizing for Specific Populations

One of the strengths of the Mifflin-St. Jeor equation is its applicability to diverse populations. For instance, when working with athletes, adjustments can be made to meet their higher energy demands. Additionally, for older adults, adjustments can be made to account for age-related changes in body composition and metabolism.

Critiques and Limitations

While the Mifflin-St. Jeor equation is highly regarded, it is essential to acknowledge its limitations and potential critiques.

Individual Variability

Like any equation-based estimation, individual variability exists. Factors such as genetics, hormone levels, and underlying medical conditions can influence an individual's metabolism. Thus, the Mifflin-St. Jeor equation provides an estimate that may need to be further personalized based on the individual's response to caloric intake.

Body Composition and Muscle Mass

The equation assumes that weight is a reasonable proxy for body composition. However, individuals with higher muscle mass tend to have a higher metabolic rate. Therefore, it is important to consider body composition measurements and adjust caloric needs accordingly.

Dynamic Nature of Energy Expenditure

Energy expenditure is not a static parameter. It can fluctuate based on various factors, including changes in body weight, exercise routine, and hormonal fluctuations. Regular reassessment and adjustments are necessary to ensure an accurate estimation of energy needs.

Other equations to calculate the basal metabolic rate:


In conclusion, the Mifflin-St. Jeor equation serves as a valuable tool for nutrition professionals in estimating resting metabolic rate (RMR) and determining caloric needs. Its accuracy, wide applicability, and validation make it a popular choice in clinical practice. By considering an individual's activity level and making appropriate adjustments, nutrition professionals can customize caloric recommendations to support weight management goals. However, it is crucial to recognize the equation's limitations and consider individual variability and factors such as body composition and dynamic energy expenditure. As nutrition professionals, understanding and utilizing the Mifflin-St. Jeor equation empowers us to provide evidence-based guidance for our clients' nutritional needs.


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