Whether you're trying to lose weight, gain weight, or stick to your current weight, you might be tempted to look up the suggested calories per day for your gender, age, and activity level. The following chart should only be used as a reference point, because every person is so different metabolically even when they are the same size and gender. The following suggested calorie ranges are generated using the Institute of Medicine’s estimated energy requirement calculation. To maintain weight, the chart below shows you your daily calorie limit. It's based on your age, activity level, and the BMI (body-mass index) of 21.5 for women and 22.5 for men. To lose weight -- It used to be recommended that to lose a pound per week you would need to decrease total calories by 500 a day. Now researchers believe weight loss is a slower process and that a decrease of 10 calories a day leads to a loss of about one pound in a year, but it can take as long as 3 years to get there. The key is to be patient and work with a dietitian to help find the right plan for you. To gain weight, it's best to work on a plan with a dietitian. Sedentary means a lifestyle that includes light physical activity associated with typical activities of daily living. Moderately active consists of walking 1.5 to 3 miles daily at a pace of 3 to 4 miles per hour (or the equivalent). An active person walks more than 3 miles daily at the same pace, or equivalent exercise