Recently I found that, there is a wrong concept to many people that drinking cold water can reduce weight. They sowed me few interesting thermodynamics prove (actually they were wrong).

They showed that if some one drinks cold water, it will be increase its temperature inside our body. In another word, it will burn few calories to increase its temperature. In this way, some one can burn their calories and can loose their weight.

They also showed me if I drink 1000g (around 1 L) water having temperature 5 deg. C and it increase its temperature 25 deg C (to reach our body temperature), then total calories loss will be 1000 X 25 = 25000 calories (as loss of calories = amount of water in grams X increase of temperature in degree Celsius). So, if some one drinks 5 L cold water, he can burn 125000 calories daily.

1g fat contains about 9.1 kilocalories. So, 125000 calories is almost equivalent to loss of 14 g fat/day, about 0.4 kg/month. Its sounds well that only drinking cold water can burn 0.4 kg fat/month.

But is it true??

The answer is NO!!

There is a difference between calories uses in physics and physiology. In physics, the amount of heat required to raise the temperature of a gram of water from 14.5 °C to 15.5 °C at standard atmospheric pressure is called 1 calorie but in physiology, the energy needed to increase the temperature of a kg of water by 1 °C is called 1 calorie. So, physiological calorie is 1000 times larger than calorie used in physics.

125000 calorie (used in physics) is equivalent to only 125 calorie (used in physiology). 125 calorie is almost equivalent to 0.01g fat. Now think, you need about 100 days to loss 1g of fat. And if you want to loss 1 kg fat, you need 274 years!!!

I think, the main reason behind the wrong concept is the conflict of two type of calorie. So don’t be confused, be confident, drinking cold water can’t loose weight.

Let's say that you need to raise the temperature of the water by 30C when you drink it (from 7C to body temperature). Using the specific heat capacity of water, we can work out that drinking a litre of water would use 125,610J of energy. That works out at almost exactly 30kcal. Using that energy you would lose 0.0039g of fat per litre of water you drink. Drink your two litres a day and you'd need 352 years to lose a kg.

It is incredibly annoying when people on TV use this information that you can "drink yourself thin" but it is usually just lazy researchers and people using their own poorly remembered, incorrect information as a source of medical advice, which then gets printed, published and broadcast hundreds of times.

Not to mention the fact that they're using one's weight as something that doesn't fluctuate. One person's weight could change daily, if you really think about it. And someone isn't going to drink just water to lose weight, they need food, so whatever fat the water got rid of, could just as easily be replaced by the days meals. Some of it isn't science, some of it is just common sense.