Ten pounds of fat equals about 3,500 calories, according to Mayo Clinic. To safely lose weight, a person should attempt to lose no more than 1 pound a week, states WebMD. Therefore, individuals should aim to reduce their caloric intake to 500 calories below maintenance levels for 10 weeks.
The number of calories that a person burns in a day depends on his sex, age and activity level, explains WebMD. It is still possible for a sedentary person to lose weight without changing his lifestyle, but he would have to consume even fewer calories than someone who leads an active lifestyle.