Typical weight loss programs use standardized calorie recommendations, which do not take your individual goal weight or other personal factors into account. If you are statistically outside the norm--taller, shorter, or more or less active than the typical dieter--these one-size-fits-all programs may not be a good fit for you. A more effective approach is to base your dietary plan on a personalized calorie-burning formula, using your goal weight as a key input.
Setting Your Goal Weight
The jumping off point in this process has to be setting your goal weight. You probably have an idea of what would be a good, healthy weight for yourself, but if you don't, rather than choosing a weight based on what some celebrity weighs or what some insurance tables say, start by finding your lean body mass [LBM] and work from there. To find your LBM, multiply your body weight by one minus your body fat percentage; that is, LBM = weight x (1 - body fat %). If you don't know your body fat percentage, you can estimate it with on-line calculators (see Resources).
Once you have calculated your lean body mass, you are ready to set your goal weight, based on your new, desired body fat percentage. To do that, take your LBM and multiply it by one plus the body fat percentage you would like to have. Healthy ranges are considered anywhere from 8 to 24 percent for men, and for women, 21 to 35 percent. The lower end of these ranges is what most of us would consider quite lean, that is, bikini-ready, yet not "model thin" or bony. The upper end of the range is what we would likely call "pleasantly plump," but is not detrimental to health.
Goal Weight Example
Let's consider an example of this process using Jane, who is a 35-year-old female who stands 5'5" and weighs 150 pounds. She has found her current body fat percentage to be 28 percent, and would like to reduce it to 22 percent:
1) Jane's LBM = weight x (1 - body fat %) = 150 pounds x (1 - 28%) = 108 pounds.
2) Jane's goal weight = LBM x (1 + goal body fat %) = 108 x (1 + 22%) = 132 pounds.
Resting Metabolic Rate
With your goal weight in hand, you can determine your resting metabolic rate for that new weight. Again, there are on-line calculators that will do this for you, but if you would like to calculate it yourself, you can use the popular Mifflin-St. Jeor equations, which were described in the "American Journal of Clinical Nutrition" in 1990. The equations look like this:
Males: RMR = 10 x weight in kilograms + 6.25 x height in centimeters - 5 x age in years + 5
Females: RMR = 10 x weight in kilograms + 6.25 x height in centimeters - 5 x age in years - 161
Continuing our example with Jane, the calculation would be as follows:
1) Jane's goal weight in kilograms = 132/ 2.2 = 60
2) Jane's height in centimeters = 65 inches x 2.54 = 165
3) Jane's RMR = 10 x 60 + 6.25 x 165 - 5 x 35 - 161 = 1,295 calories
At this point, you will have your daily resting metabolic rate--the number of calories you burn in 24 hours when doing nothing more than sitting still. You can further break that down into an hourly RMR by dividing by 24, which, in Jane's case is: hourly RMR = 1,295 / 24 = 54 calories per hour.
The Metabolic Equivalent Task
If you do more than sit perfectly still all day, which most of us do, your next step will be to include the calories you burn in activity. To do this, you must multiply your hourly RMR by the metabolic equivalent task value [MET] for the activity in question. METs are numbers like 1.4, 6.3 or 11.1. When multiplied by your hourly RMR, METs give you a personalized number of calories burned in exercise. For example, here are the METs for a few different tasks: household chores, 2.5 MET; working at a desk, 1.8 MET; competitive speed skating, 15 MET.
These are interpreted as "household chores burn 2.5 times as many calories as sitting still in a chair." There is a list of hundreds of common activities at the University of South Carolina School of Public Health website, referenced below.
Calculating Calories Burned in Activity
To find the number of calories you use each day in activity, just multiply your hourly RMR by the MET for each activity, by the number of hours engaged in that activity. For example, suppose Jane spends 30 minutes speed skating one day. Her hourly RMR is 54 calories, so when she skates, she burns 53.5 x 15 = 810 calories per hour. If she skates for 30 minutes, that is 810 x 0.5 = 405 calories total. Note that 405 is the total calories she used in that 30 minutes, counting both her RMR and her activity, not in addition to her RMR.
Calories for a Whole Day
So now, to figure out how many calories you use in a day, you need to add up all your activities for the day. Consider the following example. Jane spends her typical day in the following activities, with the following MET values: sleeping, 0.9 MET x 8 hours = 7.2 MET; showering and grooming, 2.0 MET x 1 hour = 2 MET; household chores, 2.5 MET x 2 hours = 5 MET; working at her desk, 1.8 MET x 7 hours = 12.6 MET; speed skating, 15 MET x .5 hour = 7.5 MET; reading, talking, and eating, 1.5 MET x 4.5 hours = 6.75 MET; watching TV in bed, 1.0 MET x 1 hour = 1 MET.
Her entire 24 hour day adds up to 42 MET, making her daily caloric expenditure 42 x 54 = 2,268 calories. Again, this is her total expenditure, meaning her activities amounted to 2,268 - 1,295 = 973 calories over and above her resting energy expenditure.
Final Words
Thus, theoretically, if Jane eats less than the 2,268 calories that her new, leaner figure will burn each day, she will lose weight until she reaches her goal weight. In reality, of course, it is not always so simple, since reducing calories also reduces not only the RMR, but also the rate at which calories are burned in activity, but these calculations do offer a reasonable estimate from which to work.
References
- University of South Carolina: The Compendium of Physical Activities
- "American Journal of Clinical Nutrition": A new predictive equation for resting energy expenditure in healthy individuals: Mifflin MD, St Jeor ST: 1990
- VA National Center for Health Promotion and Disease Prevention: Weight Management Program Clinical Reference Manual, November 2005
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