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Comment by xsmasher | Hacker News Reader

>Drinking water appears to stimulate thermogenesis, or heat production, in the body, particularly when it's chilled. The body has to expend energy to warm the fluid to body temperature, and the more energy expended by your body, the faster your metabolism

We did the math on the "ice cube diet" in high school physics; the energy required to melt the ice was only a few calories. Not the Kilocalories listed on food labels- actual calories 1/1000th of that unit.

If there's an effect here, it's not from heating the water.

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Agree. The article lists appetite repression and I think its 100% that.

When I diet/track calories I def load up on water to help. And for me - it does work very well.

Yup, that's it. Every time you get hungry drink a tall (TALL!) glass of water and usually the hunger goes away and you end up being content with an appropriate amount of food.

I wonder if light dehydration can mask itself as hunger? The body wants something, unsure what, many people eat.

Dehydration can cause sugar cravings.

That's actually part of the definition of a calorie: "The modern (small) calorie is defined as the amount of energy needed to increase the temperature of 1 gram of water by 1 °C"

You're not just melting ice, but actually bringing it up to body temperature.

1 cubic inch is 2.54 * 2.54 * 2.54 = 16.4 cc = 16.4 grams. 1 F = 5/9 C. The heat capacity of water is 1 cal/gm.C. So the number of calories is 16.4 * 5/9= 9.1

9.1 cal / F / cubic inch * ( 98 F - 34 F) = 582 cal / cubic inch

Edit: Yes, I realize 1 Cal = 1000 cal, I just wanted to clarify the math.

Your body is already at body temperature, and it’s at least 1000x the mass of the water, so the amount of energy required to move it to body temp is tiny, relatively speaking

> at least 1000x the mass of the water

Minor nitpick but: Typical glass of water weights 250g, but typical (even obese) human weight is very far from 250kg :) Guess you put one too many zero.

But they were talking about an ice cube, not a glass of water

You're right that that's significantly more than just a few, but it's still actual calories, not food calories.

So your math is right (I think), but the calories in food are kilocals (capital C Calories). So it's .5 Cal /cubic inch.

So 0.5 dietary calories? You're better off doing one jumping jack.

Plus the energy to melt the ice, 0.016kg * 334kJ/kg = 5334J = 1274 cal.

A grand total of 1.8kcal per ice cube. Only 1000 ice cubes and you could eat twice as much as usual!

At around 16 liters of water once melted that would be an interesting Darwin Award for sure.

I think this is easier to see if we consider a milliter of water and stick with celsius.

1ml of water weights 1 gram, and raising this ml of water one degree celsius is 1 (little c) calorie.

Drinking 1 ml of ice water (at about 0 degrees celsius) and raising it to body temperature (at about 37 degrees celsius) thus takes about 37 (little c) calories.

Thus drinking a liter of ice cold water would consume about 37 (big C) Calories.

And a pound of fat contains 3500 Calories (kcal), so drinking about 100L of ice water would consume one pound of fat.

One could drink 15L per day (about one liter per hour and 5x the recommended minimum intake) and burn about one pound of fat per week.

Or just sit in an ice bath. Also, I wonder if the reverse is true: if you drink a warm drink does that cause calories that would have been burned heating you to not be burned?

Or in metric - weight of the ice in grams, multiplied by difference in temperature of your body and the ice.

I did almost the same thing in high school physics. I felt like I'd discovered magic weight loss secrets until I took into account that food is listed in kilocalories.

Then we calculated how much liquid nitrogen you'd have to drink to offset a 2000 kcal basal metabolic rate. The volume wasn't shocking-- under 10 L, if I remember correctly. We decided it wouldn't be a very healthy diet, though.

Calories are estimation - we guess how food is consumed and gave reasonable amount of measurements for it.

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