Someone once told me that spending a lot of time in the water (like a pool) should be a good way to lose weight since water is such a good conductor of heat. Your body, then, must burn up more calories to maintain body heat. I couldn’t argue with his logic, but I don’t think it works that way in real life. Where is the flaw?
WAG time:
While water may be a good conductor of heat, you would most likely spend your time in a tub or a pool. These are restricted spaces, with a finite amount of water. Therefore, as your body heats up the water, the water becomes less of a conductor, since the temperature is rising towards your own body temperature.
Then again, that sort of logic would mean that entering a hot water tub would make you fat 
Tell your friend to go lie outside in the snow. He’ll still be fat when he freezes to death. [OK, peple stranded in snow do lose weight, but that is from lack of food.]
Do a search on the topic. It has been discussed before concerning dieting by drinking ice water, you body will have to heat that water up. Basically it works in theory but the amount is so small as to be unnoticable. One food calory is 1000 thermal calories.
Actually working out in water is good since the water provides extra resistance to movement so you work harder. Just sitting is water doesn’t do any good.
I believe if you were to plunk yourself down in the deep end of the pool (say, 15 feet deep), you’d probably lose a fair bit of weight. Treading water is good exercise.
I think your friend is thinking of the idea that exercise in water is considered a very healthy way to get fit because it doesn’t stress you out thermally. Also, certain swimming strokes are anaerobic, which I think is supposed to be very nifty for losing weight.
Plus, exercising in water does not put as much strain on joint, etc., which is why is is so often used in physical rehab.
Why do you think there’s a flaw? Have you tried it? Certainly people in cold environments can consume incredible amounts of calories without gaining weight.
There are probably reasons why it’s impractical to lose weight in this fashion. The first is that it’s just not pleasant being cold. The second is that you’d have to spend a lot of time in the water because there’s a limit to how much heat you can generate at a time. You’d have to strike a balance between hypothermia and comfort. In a 60 degree pool, you’ll lose heat much faster than in a 60 degree room, but you won’t be able to stay in the pool long enough to do much good.
The body will do what it can to minimize heat loss, including restricting blood flow to the extremities. If you remain still, you’ll probably develop a layer of warmer water around you.
I don’t have the figures in front of me now, but sitting in a cool tub for an hour or so burns a lot of calories, I think comparable to jogging for an hour. It doesn’t have to be as cold as 60F, I believe 65 or so was cold enough to have a big impact. I can post actual numbers tonight.
I’ve heard that lowering your thermostat a few degrees can make a difference, also (provided you don’t just put on a sweater).
Arjuna34
I’m sorry I don’t have time to search for and post a link, but I’ve definately read fitness reports stating those who excercise primarily in a pool have a higher body fat percentage than those who don’t. This was due to a swimmer’s body’s attempt to “insulate” itself from the effects of the cool pool water.
IIRC, this applied to those who excercised almost exclusively in a pool and of course this must be balanced against the non-impact benefits of pool excercise as mentioned previously.
Yes, swimmers in general have higher body fat than runners. Fat is more buoyant and a little more fat is actually better for a swimmer. Why they have it, even tho it is advantageous, is a mystery to me. Do those with more adipose tissue naturally gravitate to swimming? Or does something in nature promote the fat?
Swimmers do not have to fight gravity as runners do. Hence, running burns more calories thatn swimming since swimming does not require the energy expenditure necessary to overcome gravity. In fact, the buoyance of the water is an aide.
As far as the cold water is concerned, I don’t see how that would cause a calorie loss unless it involves shivering to keep warm. In a normal temperature pool (of around 80 degrees) a swimmer is not cold once he or she has warmed up with a few laps. There is no shivering. Water is a conductor, but there is no heat being exuded from the body. The heat is in the body.
According to data on the NutriStrategy* website, the following are the number or calories burned in an hour for a 155 pound person:
Running, 10 mph (6 min mile) 1126
Running, 10.9 mph (5.5 min mile) 1267
Running, 5 mph (12 min mile) 563
Running, 5.2 mph (11.5 min mile) 633
Running, 6 mph (10 min mile) 704
Running, 6.7 mph (9 min mile) 774
Running, 7 mph (8.5 min mile) 809
Running, 7.5mph (8 min mile) 880
Running, 8 mph (7.5 min mile) 950
Running, 8.6 mph (7 min mile) 985
Running, 9 mph (6.5 min mile) 1056
Running, cross country 633
Running, general 563
Running, in place 563
Running, on a track, team practice 704
Running, stairs, up 1056
Swimming laps, freestyle, fast, vigorous effort 704
Swimming laps, freestyle, light/moderate effort 563
Swimming, backstroke, general 563
Swimming, breaststroke, general 704
Swimming, butterfly, general 774
Swimming, leisurely, general 422
Swimming, sidestroke, general 563
Swimming, sychronized 563
Swimming, treading, water, fast, vigorous effort 704
Swimming, treading, water, moderate effort 281
So it depends on the type of running/swimming that a person is doing and how long that person can maintain it. Top level runners will burn more calories than top level swimmers. I think that swimming, however, does exercise more muscle groups than running. Interestingly, treading water vigourously is as good exercise (calorie-wise) as actually swimming. The chart doesn’t include any data for swimming in non-pool conditions (e.g. the ocean), which I think would require more effort.
The water will conduct heat away from the body, requiring the body to generate more heat. Finagle is right about the risk of hypothermia. If the body is losing too much heat, it will begin to shut down blood flow to the extremities. As body temperature drops, the body will shut down more and more “non-vital” areas. So trying to lose weight by swimming in 60 degree water for an hour is definitely not recommended.
- I have know idea what NutriStrategy is or what they are selling, but the data comes from the American College of Sports Medicine.