Water and caloric intake ? heat transfer

[SuperPickle]

As a member of the large group of people trying to shave pounds, I started thinking about water intake and heat transfer. I realize that the body uses water for almost all functions so let?s assume that the scenario below deals with surplus water only (ie. Water consumed exceeding the body?s need for any other purpose ? water simply excreted via urine, sweat, vapor in breath, etc.).

Water consumed at a temperature below that of the body will be heated to 37º C. It will then be excreted. The temperature difference of the water from intake to output is a loss of heat. This heat has to come from somewhere; that being from the conversion of food to heat energy.

Say, for example, one consumes 4L @ 2ºC of surplus water. Approximately how many calories from food does the body use to simply heat and excrete? How does this change if the input water is 20ºC?

I know ?food calories? cannot be converted directly to ?body temperature calories? because of the chemical processes the body uses to convert those calories to usable energy. I?m certain liberties have to be taken in computation, but I?m only looking for relative answers.

Essentially, albeit far too simplistically, I?m looking for ballpark numbers that I may assign to How much ice water do I have to drink to counter the calories in that taco I just ate?

Oh yes, feel free to point out any faults in my root logic.

 

[Matthias99]

Originally posted by: SuperPickle
As a member of the large group of people trying to shave pounds, I started thinking about water intake and heat transfer. I realize that the body uses water for almost all functions so let?s assume that the scenario below deals with surplus water only (ie. Water consumed exceeding the body?s need for any other purpose ? water simply excreted via urine, sweat, vapor in breath, etc.).

Water consumed at a temperature below that of the body will be heated to 37º C. It will then be excreted. The temperature difference of the water from intake to output is a loss of heat. This heat has to come from somewhere; that being from the conversion of food to heat energy.

Say, for example, one consumes 4L @ 2ºC of surplus water. Approximately how many calories from food does the body use to simply heat and excrete? How does this change if the input water is 20ºC?

I know ?food calories? cannot be converted directly to ?body temperature calories? because of the chemical processes the body uses to convert those calories to usable energy. I?m certain liberties have to be taken in computation, but I?m only looking for relative answers.

Essentially, albeit far too simplistically, I?m looking for ballpark numbers that I may assign to How much ice water do I have to drink to counter the calories in that taco I just ate?

Oh yes, feel free to point out any faults in my root logic.

This isn't the first time I've heard this idea. However, it basically doesn't work. While your body does have to burn extra energy to heat the cold water (it has to; the laws of thermodynamics are hard to get around), it takes a *lot* of ice water to equal the amount of caloric content in even a small amount of food.

Food "Calories" (capital C) are equal to one kilocalorie (lowercase c, used in physics equations).

If you assume that ice water (at 0 degrees Celsius) is being heated to body temperature (37 degrees Celcius), then heating up one liter of water by 37 degrees C requires (1 L * 1000g/L * 37 deg.C * 1.0 cal/g*deg.C = 37,000 calories = 37 food Calories). Considering that human caloric intake is 2,000-3,000 Calories/day, and not all of the thermal energy is being provided by directly burning stored fat, there's essentially no way to counter any meaningful part of your food intake by drinking cold water.

 

[Lynx516]

If you want to burn pounds get on a rowing machine they are one of the best for loosing fat. I row for 30mins making sure I dont get out of breath (I am doing aerobic training) and I can easily burn off 450callories (going for what the computer says).

Exersize is teh best way of loosing weight

 

[SuperPickle]

Originally posted by: Lynx516Exersize is teh best way of loosing weight

Agreed. I'm not looking for a cheap, magical way to drop pounds, I was just interested in the conversion math.

At 37C/L of energy loss, this is certainly insignificant for the average person. However, for the person that limits his or her intake to 1,500C/day and drinks an excess 4L/day of ice water, that becomes close to 10% of input energy as expelled.

Interesting. Thanks Matthias99
:beer:

 

[klah]

http://science.howstuffworks.com/question447.htm

* The temperature of ice water can be estimated at zero degrees Celsius.
* Body temperature can be estimated at 37 degrees Celsius.
* It takes 1 calorie to raise 1 gram of water 1 degree Celsius.
* There are 473.18 grams in 16 fluid ounces of water.

So in the case of a 16-ounce glass of ice water, your body must raise the temperature of 473.18 grams of water from zero to 37 degrees C. In doing so, your body burns 17,508 calories. But that's calories with a little "c." Your body only burns 17.5 Calories, and in the grand scheme of a 2,000-Calorie diet, that 17.5 isn't very significant.

But let's say you adhere to the "eight 8-ounce glasses of water a day" nutritional recommendation. In 64 ounces of water, there are 1,892.72 grams. So to warm up all that water in the course of a day, your body burns 70,030 calories

 

[TechnoPro]

Originally posted by: SuperPickle

Originally posted by: Lynx516Exersize is teh best way of loosing weight

Agreed. I'm not looking for a cheap, magical way to drop pounds, I was just interested in the conversion math.

At 37C/L of energy loss, this is certainly insignificant for the average person. However, for the person that limits his or her intake to 1,500C/day and drinks an excess 4L/day of ice water, that becomes close to 10% of input energy as expelled.

Interesting. Thanks Matthias99
:beer:

There's a minor flaw in your thinking. Assume that a dieting individual were to suddenly reduce their caloric intake by 50% from 3,000 Calories daily to 1,500, this will cause a measurable drop in the body's basal metabolic rate. Such a drastic cut in calories signals the body that food is/will be scarce, hence the body goes into a metabolically-depressed, fat-retaining state.

Yes, the individual will lose weight through the simple calorie in/calorie out equation. However, this persons metabolism will lower which is inherently counterproductive to a long-term weight reduction plan. From what I have studied, a 10-15% reduction in calories over a given 2 week span will not trigger any of the body's alarms.

On a related note, a doctor friend of mine was telling me about an intersting study. It involved the corelation between hydration levels and excercise. Besides being able to work out longer and harder when well hydrated, as well as feeling less fatigued, there was an interesting side observation. Basically, when a person didn't feel like excercising (fatigue, lack of energy, lack of motiviation, etc.), something like 70% of the time that person was dehydrated. Intersting, eh?

 

[NewBlackDak]

I find that to be true myself. If I feel fatigued for seemingly no reason it's because I didn't replace the water I used working out the day before.

 

[PlasmaBomb]

Originally posted by: TechnoPro

Originally posted by: SuperPickle

Originally posted by: Lynx516Exersize is teh best way of loosing weight

On a related note, a doctor friend of mine was telling me about an intersting study. It involved the corelation between hydration levels and excercise. Besides being able to work out longer and harder when well hydrated, as well as feeling less fatigued, there was an interesting side observation. Basically, when a person didn't feel like excercising (fatigue, lack of energy, lack of motiviation, etc.), something like 70% of the time that person was dehydrated. Intersting, eh?

I have heard of similar reports. It's interesting to note that men are more likely to be dehydrated than women as a baseline. You also need to be careful with caffeinated products, whilst a little caffeine can help you, too much can lead to dehydration and hamper performance. It's recommended that you don't drink more than 3 cups of coffee per day. Dehydration can also lead to you feeling hungry as your body misinterprets the thirst, obviously this can lead to you increasing your calorie intake when you don't need to.

 

[Tiamat]

Although you probably already know this, on top of drinking a good amount of water, excersize etc. Eating certain foods that contain extreme low calorie count can help too such as Asparagus, Celery, Apples...

More listed at the bottom of

http://weightlossinternational...ive-calorie-foods.html

The plus of eating these are that you get your vitamins, minerals, fiber without the huge caloric intake, while filling up your stomach so you arent hungry for a little while.

 

[Peter]

Sledgehammer "low calorie" diets are counterproductive when you're REALLY exercising. See also the thread we already have on this, right here on Highly Technical.

 

[edro]

It's all about eating 5-6 times a day, ~400 calories per meal. If you are lifting weights, you need at least ~150g of protein a day (Chicken breast has ~40g). That is a very simple way to put it.