Comparing Mifflin-St. Jeor and Harris-Benedict
When it comes to calculating your daily caloric needs, two formulas are consistently mentioned: the Mifflin-St. Jeor equation and the Harris-Benedict equation. Both are used to estimate basal metabolic rate (BMR) or resting metabolic rate (RMR), the number of calories your body burns at rest to perform basic functions. While the Harris-Benedict equation has a longer history, the Mifflin-St. Jeor formula is widely regarded by nutrition professionals as more accurate for today's population.
The Origins: A Timeline of BMR Formulas
- The Harris-Benedict Equation (1919): Developed by scientists James Harris and Francis Benedict over a century ago, this was the first widely used formula for estimating BMR. It was based on data from a sample of 239 subjects, but modern research has shown it tends to overestimate energy expenditure, especially in women and less-active individuals. A revision was made in 1984 by Roza and Shizgal to improve accuracy, but limitations remain.
- The Mifflin-St. Jeor Equation (1990): This equation was developed more recently, using data from a more contemporary and diverse population sample. It is particularly noted for its enhanced accuracy in both non-obese and obese individuals. Its simpler formula structure also contributes to its ease of use.
Factors Influencing Formula Accuracy
Several factors contribute to the differing accuracy of these two formulas:
- Population Data: The Mifflin-St. Jeor equation was developed using modern population data, reflecting changes in body composition and lifestyles over the decades since the Harris-Benedict formula was first established.
- Obesity: The Harris-Benedict equation is known to overestimate calorie needs in individuals with obesity. The Mifflin-St. Jeor formula was validated on a population that included obese individuals and has been shown to be more reliable for this group.
- Metabolic Changes: As with any predictive equation, individual metabolic variability, genetics, and body composition can impact the accuracy of the final number. While Mifflin-St. Jeor is more accurate for most people, indirect calorimetry is the gold standard for a true measurement of RMR.
Calculating with Both Formulas
Here are the formulas using metric measurements:
Mifflin-St. Jeor Equations
- For Men: $$(10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) + 5$$
- For Women: $$(10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) - 161$$
Harris-Benedict (1984 Revision) Equations
- For Men: $$66.5 + (13.75 \times \text{weight in kg}) + (5.003 \times \text{height in cm}) - (6.75 \times \text{age in years})$$
- For Women: $$655.1 + (9.563 \times \text{weight in kg}) + (1.850 \times \text{height in cm}) - (4.676 \times \text{age in years})$$
Comparison Table: Mifflin-St. Jeor vs. Harris-Benedict
| Feature | Mifflin-St. Jeor | Harris-Benedict | Preference | Rationale |
|---|---|---|---|---|
| Year Developed | 1990 | 1919 (rev. 1984) | Mifflin-St. Jeor | Uses more recent population data. |
| Accuracy | More accurate overall | Less accurate, tends to overestimate | Mifflin-St. Jeor | Based on multiple studies comparing measured vs. predicted RMR. |
| Obese Population | More reliable and accurate | Less reliable, significant overestimation | Mifflin-St. Jeor | Validated on a more diverse range of body compositions. |
| Formula Structure | Simpler coefficients | More complex coefficients | Mifflin-St. Jeor | Easier to calculate manually. |
| Clinical Use | Preferred for modern contexts | Historically significant, less common now | Mifflin-St. Jeor | Reflects contemporary body types and lifestyles. |
Which Formula Should You Use?
For the vast majority of individuals seeking to estimate their BMR for weight management or general health purposes, the Mifflin-St. Jeor equation is the superior choice. Its more recent development and validation on a diverse, modern population make its estimations more reliable and precise. The Harris-Benedict equation, while a historical benchmark, is prone to inaccuracies that can lead to incorrect dietary targets.
For those who are very athletic or have a significantly low body fat percentage, the Katch-McArdle formula might offer better accuracy, as it focuses on lean body mass. However, this requires knowing your body fat percentage, which is not easily accessible for most people. For everyone else, Mifflin-St. Jeor provides the best balance of simplicity and accuracy.
Conclusion: Making an Informed Decision
In the ongoing debate of Mifflin-St. Jeor versus Harris-Benedict, the former is the clear winner for most people seeking a reliable estimate of their caloric needs. The outdated population data used for the Harris-Benedict formula makes it less suitable for today's lifestyles and body compositions, often leading to overestimations that could hinder weight loss goals. By using the Mifflin-St. Jeor equation, you can obtain a more accurate starting point for determining your total daily energy expenditure and tailoring your nutritional plan effectively. While no equation can replace a direct metabolic measurement, Mifflin-St. Jeor is the most practical and evidence-backed tool for at-home use.
To find out more about the original development of the Mifflin-St. Jeor equation, see the 1990 paper in the American Journal of Clinical Nutrition.
