How many calories are in a pound of fat?

[Dahu]

Title says it all really.

I worked this out approximately as 9 calories in a g of fat, 454g per pound, so about 4,100 calories per pound.

But, googling gives a very widespread figure of 3,500 (occasionally 3,600).

So what’s the straight dope here?

I’m a runner. I burn about 500 calories per day so 3,500 per week. So my weight loss is either 0.85 or 1 pound. Right?

[friedo]

@Dahu

I’m a runner. I burn about 500 calories per day so 3,500 per week. So my weight loss is either 0.85 or 1 pound. Right?

You weight loss will be (on average) about one pound for every 3500 calories of energy deficit that your body has. Even if you burn 3500 calories running, if you spend the rest of the week hoovering onion rings and cheesecake, it’s not going to do much.

[DSeid]

FWIW the explanation of the discrepancy is given here.

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.

Of course the amount of fat lost due to your physical activity (or even weight lost) is not really a straight up linear relationship to the amount of calories you burn anyway. Other factors come into play such as how much your anabolic needs are from the activity you did (rebuilding from wear and tear even without putting on new muscle mass, putting on muscle mass, vs catabolizing muscle mass), whether or not your baseline metabolic rate is changing as a result of your activity, etc. The 1000 calorie deficit per day (of increased activity and intakes changes) leads to the ideal target of 2#/week is a great rough guide, but anyone who expects the scale to play along in a nice linear fashion because that’s how the calculations worked out may be disappointed and or pleasantly surprised by what the scale tells them any particular week, even as they are making great consistent progress independent of what the scale announces.

[Dahu]

@DSeid

FWIW the explanation of the discrepancy is given here.

That’s brilliant, exactly what I wanted, thanks. I’m just going to quote it here in case one day someone else happens by with the same question and the link is dead.

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.

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