I am told each gram of fat equals 9 calories and each gram of protein
and carbs equals 4 calories. I read the ingredients, and I can
subtract out the non-digestible carbs, but it's often not even close.
So when I read something like Dreamfields pasta has 5g of digestable
carbs and this is what they print on the Nutrition Facts:
Calories 190
Fat 1g
Total Carbs 42g
Dietary Fiber 4g
Sugars 1g
Protein 7g

How does (1g x 9 + 5g x 4 + 7g x 4 = 57) equal 190 calories? This is
just one example, of many?

Ashton

[This is a good question and labels can certainly often be confusing. There are
several things to keep in mind.
1) Dietary fiber does not mean that it is digestable and metabolizable into
calories. In fact, most fiber from grains is not digestable at all even though
it is still beneficial and correctly labeled as dietary (ie. beneficial in the
diet).
2) Carbohydrates also include starches which are all metabolized into calories,
but are seldom specifically listed on labels.
3) Depending on their amino acid profile, proteins will be metabolized into an
amount of calories somewhere between 3-4 calories per gram.

I would figure the above as:
1) Calories from carbs likely = (42 - 4)g x 4 = 152
2) Calories from protein = 7g x 4 = 28
3) Calories from fat = 1g x 9 = 9
For a total of 189 which is as close to the 190 as you are going to get with the
gross measurements available.

Actually, this one omitted some things, but overall, after using a few
reasonable assumptions, it turned out to be much less hard to fathom than many
others I have seen. --Paul]

[The trick as Paul did above is substracting the dietary fiber from the total
carbs. Since fiber is the only carb source that is non digestible doing this
should always give you a good estimate of the calories you'll get from the
carbs. -°Olafur]