Determining Your Calorie Needs
There are many different methods for estimating caloric needs. It is important to remember that these methods result only in estimates; still, you can get a general idea of the number of calories your body needs. Everyone's caloric needs differ, depending on factors such as age, gender, size, body composition, basal metabolic rate, and physical activity.
Basal metabolic rate (BMR) is the number of calories your body would burn if you were at rest all day. By figuring your basal metabolic rate, you know the minimum number of calories you must consume to maintain your weight. On average, a moderately active woman needs between 1,800 and 2,200 calories per day. A pregnant woman needs about 2,500 calories after the first trimester. However, because you don't spend every day lying in bed, you have additional calorie needs on top of your basal rate. The next section describes how to determine the number of calories you should ingest every day.
You Do the Math
Use this simple equation to figure your basic calorie needs:
First, figure your basal metabolic rate to get the minimum number of calories your body needs to maintain a healthy weight. To do this, multiply your healthy weight (in pounds) by 10. For instance, a woman whose healthy weight is 165 pounds would have a basal metabolic rate of 1,650 — in other words, this woman needs to take in a minimum of 1,650 calories to maintain her body weight. (If you are overweight, use the average weight within the range given on the Healthy Weight Chart provided in Chapter 2. Using your actual weight if you are overweight may overestimate your calorie needs.)
Figure how many additional calories you need to sustain your level of physical activity. To do this, choose the activity level from the following list that best describes you and take the appropriate percentage of your basal metabolic rate.
Sedentary — You mainly engage in low-intensity activities throughout your day, such as sitting, driving a car, lying down, sleeping, standing, typing, or reading. Take 20 percent of your basal metabolic rate (multiply by 0.2).
Light activity — Your day includes light exercise, such as walking, but for no more than two hours of your day. Take 30 percent of your basal metabolic rate (multiply by 0.3).
Moderate activity — You engage in moderate exercise throughout the day, such as heavy housework, gardening, dancing, with very little sitting. Take 40 percent of your basal metabolic rate (multiply by 0.4).
High activity — You engage in active physical sports or have a labor-intensive job, such as construction work, on a daily basis. Take 50 percent of your basal metabolic rate (multiply by 0.5).
Figure out how many additional calories you need to sustain your body's digestion and absorption of nutrients. To do this, add your results from steps 1 and 2, then take 10 percent of the total (multiply by 0.1).
To find your total calorie needs, add your basal metabolic rate from step 1, the calories to sustain your level of physical activity from step 2, and the number of calories needed for digestion from step 3. Take the example of the 165-pound woman from step 1, with the basal metabolic rate of 1,650. She is moderately active, which means she needs an additional 660 calories to sustain her activity level. She needs 231 calories to fuel her body's digestion and food absorption processes (1,650 + 660 × 0.1 = 231). Adding those values gives us a total of 2,541, which is the total number of calories a moderately active 165-pound woman should ingest to maintain her weight.
To account for the additional calories you need to sustain your body weight during pregnancy, add 300 to the total from step 4. This final value represents your estimated basic calorie needs.
A Little Extra Help
Doing the math will only give you an estimate of your calorie needs. Some women have special needs. If you are having problems figuring out your calorie needs, or if you are not sure what to eat to get those extra calories in, don't hesitate to contact a registered dietitian to help you out. Some women may need a little extra nutritional help to ensure they are getting everything that they need. It is recommended that you seek extra help if you are younger than seventeen or older than thirty-five, pregnant with more than one baby, underweight or overweight prior to becoming pregnant, a strict vegetarian, lactose intolerant, gaining too much or too little during pregnancy, having trouble eating due to nausea and/or vomiting, on a special diet due to allergies, diabetes, or gastrointestinal or digestive disorder, or if you have suffered with eating disorders. Don't go it alone if you are not sure what to do. Nutrition and calorie intake is vital to a healthy baby and a healthy pregnancy. Never hesitate to ask for help!