How Many Calories Do I Need?
Determining precise caloric need can be quite scientific and complex, but estimating a reasonable calorie level is often simple.
Caloric need is affected by age, gender, body size, body composition, fitness level, environment, food intake, daily activity level, exercise, hormonal status and health status. Energy requirement calculations usually examine basal metabolic rate (BMR) which is the amount of calories required to sustain the body when asleep for a 24 hour period. Resting metabolic rate (RMR) looks at the same 24 hour period, but is increased slightly, because the individual is awake, but not active. Daily activity not including programmed exercise is assessed, and an activity factor of 1.1-1.7 is assigned; the RMR is multiplied by this factor. Then, calories expended per week on programmed exercise, such as weight lifting, running, aerobics classes are totaled and an average calculated per day. In more extensive calculations, the thermic effect of food (TEF) may also be calculated. It should be noted that not all professionals are in agreement regarding the best formulas to estimate caloric need. Often, experience of the assessor is an important factor in the accuracy of the assessment.
A calorie need assessment might look like this:
+ 75-200 = RMR
X Activity Factor (1.1-1.7)
+ daily average expenditure on exercise
= total daily caloric need
If possible, having access to both body composition and a Resting Energy Expenditure test is very helpful for the nutrition professional trying to determine calorie need. A body composition provides information regarding the amount of metabolically active tissue. The amount of metabolically active tissue is used to calculate potential BMR, taking into account, height, age, weight and gender. A resting energy expenditure (REE) test is also very helpful. REE measures oxygen utilized and carbon dioxide exhaled which provides an indirect measure of calories burned. For a de-conditioned individual, REE may actually indicate that they are burning fewer calories than their potential according to their lean body mass (LBM). The fitter the individual, the more calories they burn.
On the other hand, it doesn’t have to be that complicated. We all eat; and we are gaining weight, losing or staying the same.
One of the best strategies for the untrained individual trying to assess their own calorie need is to first keep an accurate food journal. Then, enter the information into a good on-line food analysis program. If eating habits and weight has been stable for a while – then, this is a maintenance calorie level. If looking for weight loss, first try a modest caloric deficit of 300-500 calories per day. Many people try to cut calories too much; it causes lack of energy, feelings of deprivation and makes it harder to stick with a healthy plan for any length of time.
A word of warning: many sources advise that women attempting to lose weight go on a 1200 calorie plan, and men use a 1500 calorie plan. Our experience is that, except for small, sedentary people, those calories levels are too low. It is far better to focus on good quality nutrition choices, increased physical activity and forming positive long range health patterns than to attempt these too low calorie level diets.