Calculating Caloric Goals

To achieve your goals of controlling your glucose level, controlling your weight, and improving your overall health, you should calculate the number of calories that you need to burn each week while exercising. You and your physician or dietitian should take into account your individual health status and come up with a caloric goal to meet your needs. Typically this is somewhere between 1,000 and 2,000 kcal (calories) per week.

To determine how much you need to exercise in one week to meet your caloric expenditure goal, you need to know the amount of energy that the exercise you will engage in consumes per unit of time. An easy way to do this is to use metabolic equivalent units known as METs. This unit is a measurement of how much oxygen is consumed per unit of body weight per minute (ml O₂/kg/min), or the energy cost of a specific activity (see table 4.5). For example, if you are interested in walking for exercise, the metabolic equivalent unit of brisk walking is 4 to 6 METs. You take the average of this range (in this case 5 METs) and plug it into the following equation:

METs x 3.5 (constant) x body weight in kg / 200 (constant) = kcal/min

5 x 3.5 x 80 kg x = 7 kcal/min

When you have calculated how many calories per minute you will burn by walking, you then take your weekly caloric expenditure goal, say 1,500 calories, and divide it by the number you derived in the equation (7 kcal/min) to come up with how many minutes you must exercise per week in order to meet your goal. So in this case we would take 1,500 calories per week and divide it by 7 calories per minute and come up with 214 minutes of exercise needed per week. Then take the number of minutes you need to exercise per week and divide it up into manageable sessions, such as 45-minute walks five times a week (214 minutes ÷ 5 days = 42.8; round up to 45 minutes per day). You should experiment with this equation and come up with ideas for a manageable exercise program that will meet your caloric goals.

Table 4.5 Estimated Metabolic Equivalents for Various Activities