Factors That Affect BMR and TDEE
There are many reasons why calorie needs can be very different from one person to another, even if they have the same height or weight.
Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) are not fixed numbers. They are influenced by a combination of biological traits, lifestyle habits, and long-term adaptations.
Why BMR and TDEE Are Different for Everyone
Two people may have the same height and weight but still burn very different amounts of calories each day. This happens because metabolism is influenced by many factors, not only body size.
Age
Metabolic rate tends to decline with age. This is often due to reduced muscle mass, lower hormone levels, and decreased daily movement.
Strength training and maintaining activity can significantly slow this decline, helping preserve both BMR and TDEE over time.
Sex
On average, males tend to have higher BMR and TDEE values due to greater muscle mass and differences in hormonal profiles.
This does not mean that calorie needs are determined only by sex. Body composition and activity are also very important.
Height and Weight
Larger bodies require more energy to maintain. Height increases surface area, while higher body mass increases the energy needed to support tissue.
However, weight alone is not a complete indicator of calorie needs.
Body Composition
Muscle tissue uses more calories at rest than fat tissue. People who have more lean mass usually have higher BMR values, even if their body weight is the same as someone else.
This is one reason strength training can increase long-term calorie needs.
Genetics
Genetics influence how efficiently your body uses energy, how you regulate appetite, and how your metabolism adapts to dieting or overfeeding.
While genetics matter, behavior and consistency still play the largest role in long-term results.
Putting It All Together
BMR and TDEE are shaped by a combination of age, sex, size, muscle, movement, and genetics. No calculator can perfectly predict energy needs, but understanding these factors helps you interpret results more accurately.
The best approach is to use calculated estimates as a starting point, track outcomes, and adjust based on real-world results.