"Daily kilocalories needed = BMR x 1.9. Knowing one’s daily calorie needs may be a useful reference point for determining whether the calories that a person eats and drinks are appropriate in relation to the number of calories needed each day. The best way for people to assess whether they are eating the appropriate number of calories is to monitor body weight and adjust calorie intake and participation in physical activity based on changes in weight over time. A calorie deficit of 500 calories or more per day is a common initial goal for weight loss for adults. However, maintaining a smaller deficit can have a meaningful influence on body weight over time. The effect of a calorie deficit on weight does not depend on how the deficit is produced—by reducing calorie intake, increasing expenditure, or both. Yet, in research studies, a greater proportion of the calorie deficit is often due to decreasing calorie intake with a relatively smaller fraction due to increased physical activity. Estimated calorie needs vary by age, gender, and physical activity level. For example, estimated daily needs range from 1,000–1,400 calories for children ages 2–3, depending on activity level; from 1,600–2,200 calories for females ages 9–13; from 2,000–2,600 calories for males ages 9–13; and from 1,600–2,200 calories for females age 51 and older. For males age 51 and older, estimates range from 2,000–2,800 calories. Sedentary means a lifestyle that includes only the light physical activity associated with typical day-to-day life. Moderately active means a lifestyle that includes physical activity equivalent to walking about 1.5 to 3 miles per day at 3 to 4 miles per hour, in addition to light physical activity. Active means a lifestyle that includes physical activity equivalent to walking more than 3 miles per day at 3 to 4 miles per hour, in addition to light physical activity. The calorie ranges accommodate different ages within each group. Estimates for females do not include women who are pregnant or breastfeeding."