A serving size is the amount of food the label describes. It is not a rule about how much you need to eat. It is the reference point for the calories, net carbs, protein, fiber, and other figures on that product.
That distinction matters with bread, bagels, and pasta. One slice of bread, one whole bagel, and 2 ounces of dry pasta are three different serving units. Start with the unit before you do any meal math.
| Product | Listed serving | Calories | Net carbs | Protein | Fiber |
|---|---|---|---|---|---|
| Zero Net Carb Bread Plain | 1 slice (28g) | 45 | 0g | 7g | 7g |
| Zero Net Carb Bagels Plain | 1 bagel (56.7g) | 90 | 0g | 14g | 14g |
| Impastable Penne | 2oz dry (57g) | 55 | 8g | 4g | 36g |
Bread: calculate by the slice
The bread serving is one slice. A two-slice sandwich uses two servings, so the bread alone comes to 90 calories, 0g net carbs, 14g protein, and 14g fiber. The current bread page also states the label arithmetic behind the net-carb figure: 7g total carbohydrate minus 7g fiber equals 0g net carbs per slice.
That is the bread total, not the sandwich total. Turkey, cheese, mayonnaise, and condiments each have their own label and their own serving size.
Bagels: the whole bagel is the serving
The plain bagel serving is one whole bagel, not one half. It lists 90 calories, 0g net carbs, 14g protein, and 14g fiber per bagel. The product page gives the corresponding calculation: 14g total carbohydrate minus 14g fiber equals 0g net carbs.
If you share one bagel, divide the label figures in half. Half a bagel is 45 calories, 0g net carbs, 7g protein, and 7g fiber. Add cream cheese, eggs, or any other fillings from their own labels.
Penne: measure it dry
Impastable Penne uses a dry-pasta serving: 2 ounces, or 57g, before preparation. That amount has 55 calories, 8g net carbs, 4g protein, and 36g fiber. Water changes the pasta's weight after preparation, but it does not create another listed serving.
If you prepare 4 ounces of dry penne, that is two servings: 110 calories, 16g net carbs, 8g protein, and 72g fiber. Sauce, cheese, vegetables, and meat still need their own calculations.
The useful routine
Read the serving amount first. Decide how much you plan to eat. Then multiply or divide the label figures to match that amount. Keep the product total separate from the meal total until you add every ingredient.
Packages and formulas can change, so use the current label before you rely on the numbers. If you follow a clinician-directed food plan, use that plan for questions that need medical advice.
