Caloric intake is always an important concept to understand whether your goal is weight loss, muscle gain, or maintenance. This Infographic explains in further detail
A pound of fat contains 3,500 hundred calories and a pound of muscle contains 2,500 calories. So if someone wanted to lose 1/2 a pound of fat a week, on average, they would need to create a 250 caloric deficit per day. This could be achieved through a combination of consuming less and/or working out more.