There are three factors that determine how many calories we need daily.
Basal Metabolic Rate
Physical Activity
Thermal Effect of Food
BMR or basal metabolic rate is the amount of energy your body needs to function at rest. Your BMR accounts for 60%-70% of your daily caloric requirements. This number is different for every person. Height, weight, gender, age and activity level all affect your caloric needs. One of the most accurate methods of estimating your own BMR (the one I like) is the Harris-Benedict formula.
Here it is, get your calculators out:
Adult males: 66+(6.3xbody weight in pounds)+(12.9xheight in inches)-(6.8xage in years)
Adult females: 655+(4.3xweight in pounds)+(4.7x height in inches)-(4.7xage in years)
The second factor in the equation is physical activity. This includes everything you do, from making your bed in the morning to jogging 5 miles. This too depends on age and gender and weight. There are a number of web sites that will calculate every activity you do during the day into caloric burn. Take the time to get an “idea” of how many calories you need to get through an average day. Add this number to the BMR number that you calculated from above. (Just GOOGLE calories burned during physical activity and numerous web sites pop up.)
The thermic effect of food, the last number to calculate, is the amount of energy your body uses to digest the food you eat. To calculate this number you need to add your BMR # and your Physical activity# together then multiply it by 10%. This is your last number (thermic number).
Add these three numbers together and you should have a very accurate idea of how many calories you need to live and function. Now if you want to lose weight, subtract calories from that number, the more subtracted the quicker you will lose. (Remember 500 calories less a day will result in a loss of a pound a week) Just the opposite if you wanted to gain weight. ..R