While counting calories is not how most of us want to spend our day, it is helpful to understand how many calories our bodies need/use just to maintain weight and carry out our normal daily functions. Knowing this helps then to figure out how many calories in a day to lose weight.
There are several factors that affect the amount of calories our bodies use in a day. Gender, age, height, weight and activity level contribute to the number of calories used in a day to maintain weight. Men generally require more calories in a day than women, and people of larger stature and more muscle mass require more calories in a day.