If you’re a man, multiply your body weight by 14. If you’re a woman, multiply your body weight by 12. This will give you a rough guess at your total calories needed to maintain your body weight. Now that you’ve come up with a number for your calories, the next step is to consume calories according to this number as closely as you can for seven to ten days. Check your body weight on day one and day ten to compare.
If you lose weight, you’ve found a caloric deficit. If fat loss is your goal, this is perfect. If you lost more than two and a half pounds, however, that’s too fast, and you’re undereating. You’ll want to bump food up a bit. If you gained weight, you’re eating above maintenance. Lower your food intake by a few hundred calories and try again. You want to start with a 15 percent decrease in calories, eat that number for a few days, and then check your weight again, repeating until you find your maintenance level.
If your weight stayed the same, you found your maintenance intake. To lose fat, take about 500 calories away from your total carbs and fats. If you want to add muscle, add about 300 calories primarily to carbs with some going to fat.