Why do most cereals have the same number of calories per serving?

Dear Cecil:

Why do all cereals have the same number of calories per serving, regardless of what's in them? I have scrutinized countless nutrition labels over the years and have yet to see a cereal that didn't have 110 calories to the ounce.

Cecil replies:

Hold it right there, friend. Not all cereals have 110 calories per one-ounce serving, as you’d know if you ever spent much time in a supermarket cereals section. (Believe me, it’s a sure cure for writer’s block.) Post Grape-Nuts has 100 calories (excluding milk), while Quaker Crunchy Bran has 90. Still, many cereals do have 110, ranging from Lucky Charms to Spoon Size Shredded Wheat. The simplest explanation for this is that Food and Drug Administration guidelines for nutrition labeling require that when you have more than 50 calories, you have to round off to the nearest 10 to make things easier on the consumer. Cheerios cereal, for instance, really has 106 calories per ounce, but gets rounded to 110.

Even so, it does seem odd that most cereals have 106 to 114 calories per serving regardless of what’s in them. The reason is that, for cereals, calorie count is more a function of weight than ingredients. Protein and carbohydrates each provide about four calories per gram, regardless of the source, while fat provides nine calories. Fat content for most cereals is low — zero to two grams per ounce. You may also have a couple grams of noncaloric moisture and “ash,” the portion of a food that can’t be metabolized. With 28.35 grams per ounce, that leaves you 25 or 26 grams of carbs and protein. Add it all up and round off and you get 110 calories.

OK, but why is the calorie count for bran cereals typically only 90 per serving? Turns out you don’t count fiber, which is abundant in bran. Even though fiber is a carbohydrate, it passes through the body undigested, hence no calories. Post Fruit and Fibre, for example, has 22 grams of carbs, but 5 of those are fiber. Taking the other 17, plus 3 grams of protein and 1 of fat, gives us 89 calories, 90 rounded. I suppose it’d be nice if they explained all this on the side of the cereal box, but considering how hard it is to focus at 7 AM anyway, we’re probably better off leaving well enough alone.

Send questions to Cecil via cecil@straightdope.com.

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