KNOW YOUR NUMBERS

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep organs functioning. TDEE (Total Daily Energy Expenditure) is your actual daily calorie burn, which multiplies BMR by an activity factor. Eat at your TDEE to maintain weight, below it to lose, above it to gain. BMR alone is rarely actionable; TDEE is the number that matters for planning.

The Mifflin-St Jeor equation, published in 1990. It is considered the most accurate among the widely used formulas (Mifflin, Harris-Benedict, Katch-McArdle) for the general population. The formula is: Men: 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. Women: 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. Note: if you have measured body fat percentage, Katch-McArdle using lean mass may be more accurate.

BMI is a screening tool, not a diagnostic one. It correlates with body fat in population studies but is a crude estimate for individuals. Highly muscular individuals often read as "overweight" or "obese" by BMI while carrying very little fat. Conversely, someone with a "normal" BMI can have an unhealthy body fat distribution — a phenomenon sometimes called "skinny fat" or TOFI (thin outside, fat inside). Pair BMI with waist circumference, body fat percentage, and blood work for a complete picture.

Every 4 to 6 weeks, or whenever your weight changes by 3-5 kg. As you lose fat (and potentially muscle), your BMR decreases. Recalculating ensures your calorie targets remain accurate and you don't plateau unnecessarily. Changes in activity level — new job, new training program — also warrant a TDEE recalculation.