It definitely depends on the individual on how many calories a man or woman needs to maintain body weight. Stats such as gender, age, weight, height, medical issues, and activity level are all very important. For someone who is extremely active, an easy formula to use to figure calories would be multiplying weight by 16-22. If you want to count calories, you will have to play with these figures a bit to gauge what works best for you. As a nutritionist, I know how difficult it is for most to count calories. A good rule of thumb is to include a protein that is approximately the size of your palm for every single meal/snack. Include a vegetable and an essential fat at every single meal (skip the fat after your workout though), and include starchy carbs before and after your workout. Eat until you are 80 percent full.