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EdgarMex
02-26-2003, 08:48 PM
From what I have read all over the forums, 1 gram of carbs equals 4 calories, 1 gram of protein equals 4 calories as well and 1 gram of fat equals 9 calories. But today, after entering my meals for the day into fitday.com, I noticed that even though the grams of protein I consumed were slightly lower than the grams of carbs, the amount of calories from protein was slightly higher than the amount of calories from carbs:

Cals Grams
P - 701 175
C - 625 179

I did the math, and it turns out that for fitday.com 1 gram of protein is indeed 4 calories, but 1 gram of carbs is 3.5 calories. That means a difference of 91 calories for the figures above.

How accurate are fitday's numbers?

fuzz
02-26-2003, 08:55 PM
How much fiber did you have?

EdgarMex
02-26-2003, 08:57 PM
according to fitday, 23 grams

fuzz
02-26-2003, 09:13 PM
Thats why. Fitday doesn't count the cals in fiber towards your carb cal count.

179 total carbs - 23 fiber = 156 net carbs

156 * 4 = 624 net cals from carbs

Not sure what happened to the missing one calorie....probably a rounding error.

Originally posted by EdgarMex
according to fitday, 23 grams

02-27-2003, 04:53 AM
In reality, the 4,4,9 kcals stated everywhere are just rounded numbers.

Carbs are really like 4.1kcals (or something), protein is really 5.35kcals (but you lose about 30% via digestion so it comes out around 4kcals) and fat is something like 9.1kcals.

Something like that anyway.

I could find out for definite, but i'm lazy. All you need to know is that they're rounded. And fitday are probably working out net carbs as the above dude said.

EdgarMex
02-27-2003, 10:50 AM
Cool! Thanks for the explanation, guys

aka23
02-27-2003, 12:12 PM
The others correctly identified that the difference is cause by fiber. Some choose to subtract fiber from total carbohydrates when calculating dietary percentages since little fiber is absorbed in the body. This method is often popular when tracking carb counts with lower carb type diets.

In high fiber foods this subtract fiber method tends to underestimate calories per gram from carb, while the include all carbs method tends to overestimate grams from carb. Here are some examples that show my point:

2lb Package Broccoli (using large serving to avoid small numbers in calculations -- 263 calories, 3g fat, 49g carb, 28g protein, 27g fiber.
Using subtract fiber method -- 3*9 + (49-27)*4 + 28*4 = 227 , 227 < 263 , estimation is 36 calories too low
Using include all carbs method -- 3*9 + 49*4 + 28*4 = 308 , 308 > 263 , estimation is 45 calories too high

2 Large Apples -- 250 calories, 2g fat, 65g carb, 1g protein, 11g fiber
Using subtract fiber method -- 2*9 + (65-11)*4 + 1*4 = 238 , 238 < 250 , estimation is 12 calories too low
Using include all carbs method -- 2*9 + 65*4 + 1*4 = 282 , 282 > 250 , estimation is 32 calories too high

1 cup Black Beans -- 227 calories, 1g fat, 41g carb, 15g protein, 15g fiber
Using subtract fiber method -- 1*9 + (41-15)*4 +15*4 = 173 , 173 < 227 , estimation is 54 calories too low
Using include all carbs method -- 1*9 +41*4 +15*4 = 233 estimation is 6 calories too high

It should be clear from the above examples that the 4 calories per gram carb/protein, 9 calories per gram fat rules are just estimates.