What's the difference between BMR and TDEE?
BMR is your Basal Metabolic Rate—the calories you burn at complete rest doing nothing. TDEE (Total Daily Energy Expenditure) includes BMR plus all other calories burned through daily activities, exercise, digestion (thermic effect of food), and non-exercise activity thermogenesis (NEAT). TDEE is what you use to determine how many calories to eat for weight maintenance, loss, or gain.
How accurate is the BMR calculation?
The Mifflin-St Jeor equation is considered one of the most accurate formulas for estimating BMR, with accuracy typically within 10% for most people. However, individual variations exist due to genetics, muscle mass, hormones, and other factors. For clinical precision, indirect calorimetry (measuring oxygen consumption) is used, but the formula provides excellent estimates for most purposes.
Can I increase my BMR?
Yes, through several strategies: build and maintain muscle mass through strength training (muscle burns more calories than fat), stay active throughout the day (NEAT), get adequate sleep, manage stress, and ensure proper nutrition. Building muscle is the most effective way to increase BMR because muscle tissue is metabolically active and burns calories even at rest.
Will my BMR decrease if I lose weight?
Yes, to some extent. As you lose weight, your body becomes smaller and requires less energy to maintain. However, if you lose weight primarily through fat loss while preserving muscle (via strength training and adequate protein), your BMR decrease will be minimized. If you lose significant muscle along with fat, your BMR will drop more substantially.
Is it safe to eat below my BMR?
Short-term eating slightly below BMR (especially if still eating above 90% of BMR) may be acceptable for weight loss, but consistently eating far below BMR (less than 80%) is not recommended and can slow metabolism, cause muscle loss, affect hormones, and reduce energy levels. It's generally better to create a modest calorie deficit (10-25% below TDEE, not BMR) while maintaining adequate protein and exercise.
Why is my BMR different from my friend's even though we're similar size?
Several factors beyond size affect BMR: body composition (muscle vs fat), age, hormones, genetics, sleep quality, stress levels, and medical conditions. Two people of the same weight and height can have significantly different BMRs if one has more muscle mass or different metabolic factors. This is why the formula is an estimate—individual metabolism varies.
How often should I recalculate my BMR?
Recalculate whenever your weight changes significantly (5-10 lbs) or when your body composition changes substantially (gained significant muscle or lost significant fat). For most people, recalculating every 3-6 months or after significant weight changes is appropriate. Age changes minimally year-to-year, so that's less critical unless you're recalculating after several years.
Does muscle really burn more calories than fat?
Yes. Muscle tissue is metabolically active and burns approximately 6-7 calories per pound per day at rest, while fat burns about 2 calories per pound. This means someone with more muscle mass will have a higher BMR than someone of the same weight with more fat. This is why strength training is so important for long-term metabolic health and weight management.
Can medications affect my BMR?
Yes. Some medications can increase or decrease metabolism. For example, thyroid medications, certain antidepressants, beta-blockers, and steroids can affect metabolic rate. The BMR calculator doesn't account for medications, so if you're on medications that affect metabolism, your actual BMR might differ from the calculated value. Discuss with your healthcare provider if you suspect medications are affecting your metabolism.
Why do I need to know my BMR?
Understanding your BMR helps you calculate your TDEE and set appropriate calorie targets for your goals. It's the foundation for effective nutrition planning—whether you want to lose weight, gain weight, or maintain. You can't accurately determine how many calories you need without knowing your BMR first. It also helps you understand that a portion of your calorie needs is fixed (BMR) while another portion is variable based on activity.