Is 4cal/gram for carbs & proteins an exact number?

[romaxe]

I'm asking this because I've heard some people saying carbs and proteins have 5cal/g and also..when reading the nutrient info for certain things I buy and do my 4/4/9 calorie math..it doesn't add up properly. Does anyone know if these 4,4,9 numbers are exact? or are they just approximations?

[Kathryn]

I've never heard or read any source that says protein and carbs have 5 calories per gram. But, it's very likely that the numbers for calories per gram usually associated with macronutrients (4 for carbs and protein, 9 for fat, 7 for alcohol...which isn't really a macronutrient, but it does have a different calorie count) are rounded up or down. So maybe protein is something like 3.9 and carbs are 4.2.

[Odidnetne]

Well, it's not even that. It might be that the amount of protein/fat/carbs in the product you're consuming is just rounded down or up.

 

For instance, if you had 6.5 grams of protein, that's 26 calories.

[romaxe]

i've just heard that protein actually has 5 but because nitrogen is not used as nergy it's considered as 4 calories.

[joelbct]

I think I remember from chemistry class that the 4/4/9 is exact, they calculate it by the molecule or something- I'm sure you could search for nutrition or chemistry or nutritional chemistry on www.wikipedia.org for an in depth explanation-

 

JB

[romaxe]

oh well..ill just stick with 4/4/9