Knowing how many calories we burn is probably the most important factor to pay attention to when our main goal is lose weight. It is not about basing all our efforts on that single measure, but becoming aware of it.
Although most of us understand this reality, the problem for many begins when it comes to finding a method to know for sure how many calories are lost daily with the exercise that is carried out.
Mathematical formulas, measuring machines or predetermined scales are the methods we usually go to, but: which of these is the most indicated in each case? Discovering this is easier than you think, and also fundamental.
How to know how many calories are burned by exercising
1. How does science measure energy and caloric expenditure?
When we talk about burning calories , we also talk about expending energy, because that is precisely what calories are: sources of energy that our body stores.
Science has understood this relationship for quite some time, and that is why it has used it to develop various measurement methods. However, there is one that has become basic, and it is known as indirect calorimetry .
1.1 Indirect calorimetry method
As its name implies, indirect calorimetry measures your energy expenditure through an indirect element, which is respiration: it is about measuring the levels of oxygen (O2) and carbon (CO2) that are inhaled and exhaled. , and through this balance find the total energy expenditure of an activity .
It is a fairly precise method, since there is a direct relationship between gases and energy: only a small part of the oxygen that we inhale is converted into energy, so the more O2 the body asks for, the greater the energy expenditure, and the less it is exhale, the greater the energy that is produced.
1.2. Double marked water method
The double labeled water method is even “more scientific”, requiring the individual to drink water with special compounds that remain in the body before starting physical activity. At the end of the routine, the researchers measure how many of these special substances were eliminated through sweat, saliva or urine, and use that data to determine how energy expenditure was.
The idea is that the more energy is expended, the faster compounds will move through the body.
1.3 Disadvantages of these energy expenditure measurement methods
The disadvantages of these precise measurement methods are obvious: they are time consuming, cannot be done without specialist assistance, and cost quite a bit of money.
So that we do not need them, science has designed approximate scales and invented devices that help us measure our caloric expenditure in a relative way . But: How accurate are these methods?
2. Alternative methods of calorie burn measurement
2.1 Activity trackers
Activity trackers have become fashionable for basically two reasons: because they look like accessories, and because they have been sold to us by advertising as if they were a marvel in terms of accuracy. The first is a matter of taste; the second, not so much. Unfortunately for many, studies have shown that activity trackers are not accurate .
These devices work with an integrated accelerometer, which measures the speed of movement, -mainly of our steps- and through an algorithm it gives us a final data of calories burned.
The problem is that this only works with certain specific activities, but if you do the same movement adding another factor – let’s say: an extra weight – the input data is damaged, and therefore the final result as well.
2.2 Gym machines
For quite some time, gym machines, especially cardio machines, have come with built-in computers that use our movement in the machine to calculate the number of calories we burn.
This may seem like a more accurate measurement method, but the truth is that most machines tend to exaggerate the amount of calories burned that appear on the screen. Some studies have pointed out this, with elliptical machines being the ones that ended up being considered less accurate.
The result of the machines usually differs from brand to brand – some are more precise than others, obviously – but in general terms, the algorithm of these devices has a flaw: if a more obese person, for example, performs an exercise during the the same time and intensity as a slimmer person, the effort and, consequently, the energy expenditure will not be the same.
Virtually no machine asks people for this kind of information, preferring to base its measurement algorithm on a more or less intermediate point, but still not very precise.
3. How do we know how many calories we really burn per day?
So far the picture looks bleak: studios are expensive and complicated, while home and gym machines are highly imprecise. What can be the solution?
The good news is that the methods don’t end here; in fact, there is one that is quite accurate, and you can do it on your own: the metabolic equivalent of task , MET, for its acronym in English. This scale, instead of measuring the amount of energy required to burn one kg of water in degrees Celsius, focuses on how much energy an average person expends simply while sitting .
3.1 How to measure calories expended with the metabolic units method
- The equation you will use is this: “calories burned = MET (s) multiplied by your weight in kg, multiplied in turn by the hours of activity”.
- Look on the MET scale for the type of activity you want to do and add your weight.
- Finally, put the amount in hours that it will take you to do the exercise.
- Imagine a case where your activity represents 6 METs, your weight is 80 kilograms and you plan to do it for an hour: 480 would be the number of calories you would burn.
By applying this method correctly, you will be able to know how many calories you burn in each activity in a fairly precise way, and have better control over your training goals.
Reference
- Matthews, M. How Many Calories Do You Really Burn Every Day? For Legionathletics. [Revised November 2016]
