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On Apr 27, 2004 at 4:14 pm robert skversky m.d. wrote:

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does additional 7 lbs of weight loss due to xenical mean that one would have to have consumed @75000 calories of fat to block @30 %=@25000 calorieswhich equals 7 lbs.

On Apr 27, 2004 at 4:57 pm Larry Hobbs wrote:

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Robert,

That's a good question.

It's obvious that this cannot be true. The studies do not last nearly long enough for people to be consuming this much fat.

If a person consumes 100 grams of fat per day, it would take them 750 days or 2 years to consume this much fat, and the studies have not lasted nearly this long.

(And I would calculate the number to be even higher than you did, more like 95,000 calories of fat, which would take a person 2 years and 10 months to consume this much fat. One pound equals 454 grams multiplied by 9 calories per gram of fat equals 4086 calories per pound of fat multiplied by 7 pounds equals 28602 calories of fat in 7 pounds divided by 0.3 (because 30 percent of fat is blocked) equals 95340 calories of fat of which 30 percent or 28602 are blocked.)

I assume that much of the difference in weight loss between the people taking Xenical and those taking a placebo has to do with the placebo group not sticking to their diet and eating more than is recommended.

On Apr 27, 2004 at 6:53 pm robert skversky m.d. wrote:

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larry, I admit i'm a bit confused, but why quibble over a mere 20,000 calories of fat!! If someone loses 4 lbs of weight based on diet and let's assume it is all fat and no lean body mass does that equal 14,000 calories lost; whereas if the same 4 lbs is lost due to xenical alone (no diet) is it then a loss of 16,344 calories ?

On Apr 27, 2004 at 7:28 pm Larry Hobbs wrote:

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Robert,

No, both equal 16,344 calories of fat.

Four pounds of fat equals 16,344 calories regardless of whether it is from Xenical or diet and exercise.

(One pound = 454 grams X 9 calories per gram of fat X 4 pounds = 16,344 calories in four pounds of fat.)

Most of the time if someone loses 4 pounds, the assumption is that the weight loss is 3/4 fat and 1/4 lean body mass. Therefore they multiply 3/4 of the weight loss by 9 calories per gram (the fat loss), and the other 1/4 by 4 calories per gram (the loss of protein) which works out to 3500 calories per pound.

But if it is all fat loss, then one pound of fat equals 4086 calories (9 calories per gram X 454 grams in a pound = 4086 calories).

On Apr 27, 2004 at 8:09 pm robert skversky m.d. wrote:

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larry, thanks for the math lesson. r

On Apr 28, 2004 at 8:27 am Larry Hobbs wrote:

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Robert,

You're welcome.

On Sep 08, 2004 at 11:50 am Rian Mullins wrote:

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I've been wondering how 454 g/lb x 9 cal/g = 3500 cal/lb ! Thanks for clearing that up.

But I must point out that 454 X 9 is not equal to 4086, in science; the best we can really say is that it is 4000 calories per pound until we get more significant figures on 9 calories/g.

I saw something the other day that said "Stay at least 6 inches (152.4 mm)away at all times."
And I imagined someone with a micrometer making sure he wasn't 152.3 mm away. And the 6 isn't even 1 significant digit, it is half a foot, which is a more vague reference than 6 inches.

On Sep 08, 2004 at 12:35 pm Larry Hobbs wrote:

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Rian,

If I understand your question, here is how it works.

How many calories are in a pound?

It depends.

It depends on whether it is a pound of fat, or a pound of muscle, or a mixture of both.

One pound equals 454 grams.

Therefore, a pound of fat contains 4086 calories.

It is calculated as 454 grams X 9 calories per gram of fat = 4086 calories.

A pound of muscle (protein) contains 1816 calories.

It is calculated as 454 grams X 4 calories per gram of fat = 1816 calories.

My understanding of how they came to say that one pound equals approximately 3500 calories, is that they assume that most weight loss consists of roughly 3/4 fat and 1/4 muscle.

So 3/4 of a pound of fat contains 3065 calories, calculated as 4086 calories X 0.75 = 3065.

And 1/4 pound of muscle (protein) contains 454 calories, calculated as 1816 calories X 0.25 = 454.

If you add the two together, you get 3065 + 454 = 3519 calories.

Therefore, they say that a pound of weight loss contains roughly 3500 calories.

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I agree with your second statement -- that fat does not contain exactly 9 calories per gram.

The same is true of carbohydrates and protein -- they do not contain exactly 4 calories per gram.

They are just approximate values.

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I agree with your third statement about significant digits.

I also think it is more difficult for people to comprehend or remember numbers containing several decimal places.

I think it is much easier for a person to remember a story when weight loss is shown as 25 pounds versus 18 pounds, rather than 25.2 pounds versus 17.7 pounds, or worse yet, 25.19 pounds versus 17.73 pounds.

I usually try to limit numbers to one decimal place just for the sake of accuracy.

Thanks for your comments, Rian.

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