The math doesn't quite work on 1 pound of fat = 3500 calories

So, this has been bugging me.  I constantly hear and read that you need to eat 3500 extra calories to gain a pound of fat, and 3500 fewer calories to lose a pound of fat, but I can't for the life of me figure out where they got that number.  Here goes:

There are 9 calories per gram of fat.

Therefore there are 9000 calories in a kg of fat.

There are 2.2 lbs/kg, so 9000/2.2 = 4091 cal per pound of fat.

If they had rounded it down to 4000 calories, I wouldn't complain, but for there to be 3500 calories in a lb of fat, 1 gram of fat would need to contain only 7.7 calories of energy.  That's a significant difference.

you can't equate a gram of body fat to a gram of dietary fat, otherwise you would basically saying we only gain weight when we eat fat, which we know is not the case.

there are 4 calories per gram of carbs or protein...which would mean that it would require 3500/4 cals per gram = 875grams of carbs or protein to net 3500 calories, and 875 grams = .875kg which = 1.92 pounds, not 1 pound.

what i'm saying is that the 9cal/gram doesn't translate directly into the 3500 calories needed to gain a pound. you can't simply say one gram of dietary intake = one gram on our bodies. it just doesn't work that way. now, the way it DOES work is beyond me, but if you think about it, it wouldn't make sense to calculate it in this way because carbs and protein yield less than half of the calories than fat does for the same amount of weight, and we know that you can definitely gain weight on carbs and protein and overeating fats is no worse than overeating the other macronutrients. i don't know if this makes sense but it's a bit abstract. hope you can kind of make sense of it!! :)

i found this from caloriesperhour.com

As you will learn in the topic Calories in Protein, Fat and Carbohydrates, it is commonly said that a gram of fat contains 9 calories. But there are 454 grams in a pound, and 9 x 454 = 4086 calories, not 3500.

The reason for the discrepancy is that body fat, or adipose tissue, contains not only fat, but also other substances including protein, connective tissue, and water. The dietary fat referred to in the nutritional analysis of food is pure.

Looking at it another way, 3,500 / 454 = 7.7 calories. Thus a gram of body fat contains only 7.7 calories versus the 9 calories found in pure fat. It's easy to see that there should be a difference when you consider that body fat contains water, which has no calories.

Because of the differences in the two types of fat, it is appropriate to use the 3500 calories per pound figure when discussing fat "burned" by activity, and the 9 calories per gram figure when discussing the nutritional content of food.

Hope that clarifies it a bit!!

When weight is lost, it is never 100% fat. When we lose weight, we lose a combinatin of fat, muscle and water. Not sure how much of each is lost in each pound, so I can't throw any calculations out there, but we don't lose pure fat.

Original Post by chrissy1988:

i found this from caloriesperhour.com

As you will learn in the topic Calories in Protein, Fat and Carbohydrates, it is commonly said that a gram of fat contains 9 calories. But there are 454 grams in a pound, and 9 x 454 = 4086 calories, not 3500.

The reason for the discrepancy is that body fat, or adipose tissue, contains not only fat, but also other substances including protein, connective tissue, and water. The dietary fat referred to in the nutritional analysis of food is pure.

Looking at it another way, 3,500 / 454 = 7.7 calories. Thus a gram of body fat contains only 7.7 calories versus the 9 calories found in pure fat. It's easy to see that there should be a difference when you consider that body fat contains water, which has no calories.

Because of the differences in the two types of fat, it is appropriate to use the 3500 calories per pound figure when discussing fat "burned" by activity, and the 9 calories per gram figure when discussing the nutritional content of food.

 

Hope that clarifies it a bit!!

OK, that makes sense.  Body fat isn't just made up of fat, so when we call it "fat," it's kind of a misnomer.  It's the stored fat combined with everything that holds it together.  Thanks.

Hey thanks for asking the question dolphinclick. I didn't do the math, just took the figure as shown but it is definitely good to know how it is calculated.

Just to make matters worse - while there are 4000 calories or so in a pound of fat - you need to burn about 6500 calories to lose a pound of fat.

legaleli, do you want to elaborate on how you came up with that number?

Original Post by tattooed_kitty:

When weight is lost, it is never 100% fat. When we lose weight, we lose a combinatin of fat, muscle and water. Not sure how much of each is lost in each pound, so I can't throw any calculations out there, but we don't lose pure fat.

 i've been curious about this. while i'm not comfortable with your "never" statement i'm interested in knowing more about the combination loss.

There have been studies that have shown that dieters lose muscle and bone mass along with their fat.  However, if weight loss is combined with strengthening those muscles, not only do you not lose muscle and bone, you may actually gain some while you lose the fat.  I've seen this information over many years, but most recently I've read them in "Strong Women Stay Slim" and "New Rules of Lifting for Women".  As to how many calories it takes to lose a pound of fat, I have no clue.

Original Post by dolphinclick:

legaleli, do you want to elaborate on how you came up with that number?

The bottom line depends on the size of your bottom – making it the “bottom line” I guess!  The more fat you have, the less muscle you’ll lose per pound of fat loss.  As you approach thin it gets harder and harder to lose fat without eating away considerably at your muscle.  It is absolutely TRUE that a weight training program will help mitigate this loss.

Personally I think this topic is far more important than the whole metabolism argument (the ups and downs of metabolic change).

The topic – if you want to GOOGLE it – is called “partitioning”.  Google “weight loss partitioning” or “fat muscle partitioning”.

http://www.bodyrecomposition.com/muscle-gain/ calorie-partitioning-part-1.html