The Master Formula (Mifflin-St Jeor)

Dimensional Analysis

The units for each term must be $Energy/Time$. Since the formula is empirical, the constants $(10, 6.25, 5)$ carry the necessary units to convert $kg, cm, \text{ and years}$ into $kcal/day$. This is a Phenomenological Equation, common in engineering and medicine where fundamental laws are too complex to apply directly.

Activity Multipliers (The "PAL" Cheat Sheet)

• Sedentary: $1.2$ (Office job, no exercise)
• Lightly Active: $1.375$ (Light exercise 1-3 days/week)
• Moderately Active: $1.55$ (Moderate exercise 3-5 days/week)
• Very Active: $1.725$ (Hard exercise 6-7 days/week)
• Extra Active: $1.9$ (Physical labor or professional athlete)

Shortcuts & Mnemonics

• The "Rule of 24": For a very rough BMR estimate, multiply body weight in kg by 24 (for men) or 22 (for women).
• Mnemonic: "Weight-Ten, Height-Six, Age-Five, and the Gender-Fix." (Remembering the coefficients $10, 6.25, 5$).

Edge Cases

• Starvation Mode: During extreme calorie deficits, the body lowers BMR to conserve energy (Adaptive Thermogenesis). This is a non-linear feedback loop.
• Fever: For every $1^\circ C$ rise in body temperature, BMR increases by about $13\%$. (Direct application of the Arrhenius Equation logic).
• Post-Exercise Oxygen Consumption (EPOC): TDEE remains elevated for hours after a workout—the "Afterburn Effect."