Weight loss or gain is all about calorie deficit or surplus governed by the simple equation: Calories In (Eating) - Calories out (BMR + Activity). If calories In > Calories out, it is a surplus, and you will gain weight. If Calories in < calories out, it is a deficit and you will lose weight. Any diet or exercise regime, no matter how fancy, aims to create this balance. By decreasing calories in through a controlled nutritious diet, and increasing the activity by exercise and activity there is a calorific deficit that is created which leads to weight loss.
There are 4 components of Total Daily Calorie Expenditure:
- BMR (Basal Metabolic Rate) or RMR (Resting Metabolic Rate): denotes the calories the body requires at rest. This includes the energy needed for body functions at rest to maintain essential life-sustaining functions such as breathing, heartbeat, and brain function. This is 70%-80% of TDEE. This is the majority of the daily calorie expenditure.
- Non Exercise Activity Thermogenesis: This denotes the calories burnt while doing daily activities and movements that are not qualified as “exercise” like chores, walking, etc. This could range anywhere between 15% depending on activity level. Most of us live sedentary lifestyles and are pretty low here.
- Exercise Activity Thermogenesis: This is energy required for planned exercise activity like gym, running, sport etc. This counts for anywhere between 5-10%
- Thermic effect of Food: This is the energy needed by the body to perform digestion and absorb food. This is minimal and possibly accounts for 8-15%.
In order to determine how many calories should one eat - The Mifflin St. Jeor Equation is one of the best approximations that exist today to calculate BMR - the Basal Metabolic Rate. Use the calculator below to estimate your BMR to give you an indicator of how much calories you require in a day.