When drinking cold water, our body burns calories, bringing it to thermal equilibrium with the body at a temperature of approximately 37 ºC. Thus, it is natural to imagine that the consumption of cold water helps in weight loss, but this concept is wrong.
All the foods we eat provide us with the energy necessary for the body’s vital functions. Although there are exceptions, the human body needs, on average, an intake of 2000 kcal (kilocalories) daily. In practice, this means that if our body consumes more calories than we eat, we lose weight.
In this context, what is the impact of a glass of cold water on our daily calorie intake? For this, we will use a well-known equation: the fundamental equation of calorimetry, used to calculate the sensible heat.
In the above equation, Q is the amount of heat, which can be measured in calories (cal) or Joules (J); m is the mass of the body in grams (g); c is the specific heat of the water in lime / g ºC (or lime / g.K); and ΔT is the temperature variation suffered by the body in ºC or K (the temperature variation in these two measurements is the same).
Based on the equation, we will answer the following question: How many calories do you need to heat a 200 ml glass of ice water at 4ºC, up to the equilibrium temperature with the human body (37ºC)? The specific heat of the water is 1.0 cal / g ºC, which means that, to vary the temperature of 1 g of water in 1ºC, 1 cal is consumed. Observe the following calculation:
In the calculation above, we used 200 g for the body of water, as its density is 1.0 g / ml. The result indicates that if we ingest 200 ml of water at 4ºC, at least 6.8 kcal (6800 cal) will be consumed. Regarding the daily caloric intake, of approximately 2000 kcal, this result is practically insignificant, as it represents less than 1% (0.3%) of the total calories we eat.
Some calculations indicate that to lose 1 kg of fat, it is necessary to consume about 7500 kcal by performing physical activities or reducing caloric intake. To achieve the same thing with the intake of cold water (at 4 ºC), it would be necessary to consume about 220 liters – an impractical amount, large even for a period of one month. Therefore, there are more viable strategies for losing fat, such as decreasing calorie intake and regular physical exercise. It is worth saying that this does not imply reducing water consumption, since it is extremely important for the entire metabolism of the body.
By Rafael Helerbrock
Graduated in Physics