Carbohydrates and proteins both have about 4 calories per gram, fat has 9 and alcohol 7.
Let’s say, you have a food and know that it contains 10 grams of carbs, 3 grams of protein and 2 grams of fat.
10 x 4 = 40 calories from carbs
3 x 4 = 12 calories from protein
2 x 9 = 18 calories from fat
This food has a total of 70 calories.
To determine the percentage of carbohydrates of the total calories:
40 (calories from carbs) x 100 divided by 70 (total calories) = 57 %.
Hope that answered your question.
Karin’s answer is right on point. Just keep in mind that carbs come from both simple sugars (glucose, fructose, maltose) and from complex carbs. The complex carbs take a bit longer to digest, so the impact on blood sugar will be a bit delayed. 4 calories/gram is an estimate, but it works well in calculations. Likewise with protein (4 cal/gr) and fat (9cal/gr). You can easily estimate the % of total calories from each of these nutrients with a little simple mathematics.
You may easily calculate carb’s and proteins using “New American Plate”. This includes 1/2 plate of vegetables, 1/4 plate of meat, and 1/4 plate of starch.
You can go to the MyPyramid Web site (www.mypyramid.gov)
With regards, Miroslava.