According to the National Health Service (NHS), UK, the average male adult needs approximately 2,500 calories per day to keep his weight constant, while the average adult female needs 2,000. US authorities recommend 2,700 calories per day for men and 2,200 for women.Jan 11, 2016

More specifically, sedentary women require 1,600 to 2,000 calories a day, while sedentary men need about 2,000 to 2,600 calories daily to maintain their current weight. As a general rule, calorie needs for healthy weight maintenance in adults decrease with age.

While a brain takes up about twenty percent, or 300, of a resting body's 1300 calories a day, and while it has the potential to burn more, it's estimated that most actual thinking only changes the amount of calories that the brain burns by around twenty to fifty calories per day.Jun 25, 2012