A few foods like table sugar and lollipops are entirely carbohydrate, so their weight on a gram scale will be exactly the same as the number of grams of carbohydrates they contain. Most foods, however, have only part of their total weight as carbohydrates. The carb content of these foods can be determined by food labels, reference books or software, or a scale and a list of carb factors.
Like any new skill, counting grams of carbohydrates will take a couple of weeks to master. You will need to consult books or software and weigh and measure foods consistently for a while. As time passes, you will train your eye to estimate accurately both serving sizes and weights, whether eating out or at home. As you look up the foods you commonly eat, make a list of them for easy reference. Keep that list next to your Smart Charts or food log, and use it to figure the carbs in a meal before you decide how much insulin to take.
Truly accurate carb counting requires some weighing and measuring equipment, such as a gram scale and measuring cups and spoons. Remember that scales measure weight while measuring cups and spoons measure volume. For some foods, there is a big difference. For example, ten ounces of Cheerios® by volume (1 1/4 cups) is equal to one ounce by weight (28 grams). Many nutrition labels and food composition tables give both types of measure, but some give only one. Just be sure to match your type of measurement, i.e., weight or volume, with the reference material you are using. To do otherwise will require considerable calculation.
1. From Labels
Advantage: Relatively easy with minimal calculation required.
What you need: Varies. For the container of yogurt, a spoon and your pump will do. Food labels, measuring cup, and a calculator to calculate the carbs in an amount with other foods and other portion sizes you plan to eat when it differs from the portion size on the label. If you have a pump with no built-in carb factor adjustment, a pocket calculator will come in handy as well as tools to measure your preferred serving size.
How: Food labels contain all the information you need to do carb counting. Just be sure your serving size is the same size as the serving on the label, or calculate on the basis of the amount you’ll be eating.
For example, let’s say you want to eat an 8-ounce carton of low-fat yogurt. The label tells you that one cup or 8-ounce serving contains 18 grams of carbohydrates. Once you know this and your carb factor, or how many grams of carbohydrate you cover with one unit of insulin, you can calculate the carb bolus required to cover the yogurt. If the serving you eat differs from the serving size listed on the package, you will have to weigh or measure your actual serving and do some minor calculations to determine your carb bolus.
2. From Books, Software and Cookbooks
Advantage: Nutrition books and software may provide information useful for food eaten at home and in restaurants. They also provide an easy way to look up brand name foods. Many cookbooks provide carb information for easy counting when preparing meals at home.
What you need: Books or software programs with a food database. You may also need measuring cups, spoons, and scales to determine serving size.
How: Look for books and cookbooks in the “Nutrition and Diet” section of your local bookstore and library, or in online sources like the Diabetes Mall (www.diabetesnet.com). Online sources and diabetes product guides from diabetes magazines, such as Diabetes Interview and Forecast, also list software and written sources. Look for recipes that have the carb content in the “Food” section of your local newspaper and in magazines related to health.
Nutrition books, software, and newer cookbooks, similar to nutrition labels, list the amount of carbohydrate in a typical serving size of each food. If what you eat varies from this serving size, you may need to weigh or measure your actual serving, and you’ll need to do the necessary calculations to convert your serving into the grams of carbohydrate eaten.
3. With A Scale
Advantage: Convenient for measuring carbs in odd-sized foods like fruits, unsliced bread, soups, or casseroles.
What you need: A gram scale, a calculator, and a list of carb percentages like those in Appendix A at the back of Using Insulin, or a computer scale.
How: Find the amount of carbohydrate in a serving of food:
- Weigh the food to find its total weight in grams. Note that the total weight of the food is not how many grams of carb in the food.
- Find the food’s carb percentage in one of the food groups listed in Appendix A.
- Multiply the food’s total weight in grams by its carb percentage.
- The result of this multiplication gives the number of grams of carbohydrates that the food contains.
Say you want to have a piece of French bread with dinner. You remove a piece from the loaf and place it on a gram scale. Your scale tells you it weighs 80 grams. In Appendix A of Using Insulin you find that the Carb Factor for bread is .50. (Meaning that 50% or half the total weight of bread is carbohydrate.)
You then multiply its weight (80 grams) by .50 to find out how much carbohydrate you will be eating:
80 grams of French bread X .50 = 40 grams of carbohydrate
You will be consuming 40 grams of carbohydrate from this French bread.
As another example, one gram of apple has 0.13 grams of carbohydrate, so 100 grams would have 13 grams of carbohydrate. Another way of saying this is that 13% of any apple’s weight is carbohydrate (most of the rest is water).
We then know that 100 grams of apple will raise the blood sugar approximately:
13 grams x 4 points per gram = 52 points (unless countered with insulin or exercise)
The Carb Factors for a variety of foods have been listed.