Sabira,
The number of calories our cells burn to function well can be complicated. The number is different for each person, depending on height, weight, gender, age and activity level.
Three primary factors are involved in calculating how many calories your body needs per day:
* Basal metabolic rate
* Physical activity
* Thermic effect of food
Not sure if this answers your question. Hmmm.. perhaps I need to write an article about this!