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The caloric expenditure of the muscle at rest is not what you expect

“You can afford these whims because then you burn it.” This forceful affirmation is the one that any sports person hears almost every day, because rare is the day in which they do not make an exquisite gastronomic offer to the palate, but poor in terms of its contribution to good health. This belief is due to the constant publication of articles insisting that gaining muscle dramatically increases daily energy expenditure. And on top of that, this happens even while resting. Recently, the athlete and popularizer greg nuckols in his ‘Stronger by Science’ blog (an essential source of knowledge), he explored in detail the extent to which this was true. I already anticipate that not so much, or at least not enough so that someone who wants to take care of themselves can be eating badly every day ‘because he or she burns it’. The information that Nuckols exposes almost always implies dedicating some time to reading, which is why I anticipate that today’s article is a dense one, unfit for lovers of pills with a ‘reggaetonero’ dance from TikTok, or of miraculous and simple promises.

What does science say?

Skeletal muscle only burns about 13 calories per kilogram a day at rest, as can be verified in some medical study. If we do a quick calculation, this would mean that by managing to gain five kilos of clean muscle mass, something that may sound little like that but is not at all, our basal metabolism would have increased by 65 calories/day, that is, a little more than Two Maria biscuits or not even half a croissant Outrageous!

However, the reality is not so simple since the basal metabolic rate specific to muscle tissue is only a part of your energy expenditure. To know the total consumption, there are different calculation methods. Nuckols remembers to classify the energy expenditure into two groups: active and non-active energy expenditure.

He non-active energy expenditure includes basal metabolism (the energy we expend simply by being alive: keeping our organs working, carrying out basic cellular processes, etc.), and the thermic effect of food (the energy we burn to digest, absorb, and metabolize food ). He active energy expenditure it includes everything else: from watching TV thinking about shrews to running a marathon.

Any muscle gain affects both types of energy expenditure. The 13 calories per kilo a day in the previously exposed research only account for the effects of muscle on non-active energy expenditure, so it is missing estimate the impact of our muscle mass on active energy expenditure. To do this, one must rely on a simple relationship: under a given level of activity, active energy expenditure increases linearly with our body mass. Calories are a unit of energy, and energy expenditure increases with the amount of work we do. Let’s stop thinking about dumbbells and cream-filled puffs and apply the physical definition of work: Work = Force × Distance, where Force = Mass × Acceleration. So, Work = Mass × Acceleration × Distance. In other words, if acceleration and distance remain constant (practically explained, if you move the same amount and in the same way), work, and therefore energy expenditure scales approximately 1:1 with mass.

If the mass you move increases by 1%, your active energy expenditure should increase by approximately 1%, assuming your activity levels don’t change. That’s true regardless of whether the increase in overall mass is due to muscle gain, fat gain, increased hydration, or because you like to hike with a fully loaded backpack.

So how can we estimate active energy expenditure?

Nuckols proposes some simple mathematical operations that begin with the calculation of our total energy expenditure per day. Before, it is convenient to have an estimate as approximate as possible of the daily calories that you need to eat to maintain our weight, or what is the same, calculate the daily intake of foods that provide us with some calories equal to our total daily energy expenditure or maintenance calories (something that can be achieved with a nutritionally poor diet, beware that it is not the same). It is here where the figure of the nutritionist is very important if you do not have experience, stop seeing this professional sector as people to go to only to ask for weight loss diets.

Well, we start with the calculation of your total daily energy expenditure. Having tracked our meals and with a pretty good idea of ​​those maintenance calories, let’s use that number, which by definition should be roughly equal to your total daily energy expenditure.

Next, subtraction your non-active energy expenditure to total daily energy expenditure. To carry out this operation we must calculate our basal metabolic rate (you can find calculators online) and the thermic effect of our diet. The thermic effect of feeding is approximately equal to 10% of total energy intake. Therefore, assuming we do not have a significant energy surplus or deficit, we can use 10% of our total daily energy expenditure as a rough estimate. Subtracting our basal metabolic rate and the thermic effect of eating from our total daily energy expenditure would give us an estimate of active energy expenditure.

If we divide our active energy expenditure by our weight, we will have the estimate of active energy expenditure for each kilo of body weight. Following the above, gaining or losing a kilo of any tissue (including muscle) should increase or decrease our active energy expenditure by approximately that number that we have calculated. Now that we know how much both our active and non-active energy expenditure would increase per pound, you know how much your total energy expenditure increases per pound of muscle.

Where is the caloric expenditure of the exercise in all these calculations?

The simplicity of these calculations is based on an estimate of the calories consumed in our diet balanced with our needs (what would be considered a maintenance diet). I think that all these calculations normally end up in the trash either due to absolute ignorance on how to make an objective and adjusted calculation of our daily caloric intake, or if we enjoy excessive complacency when it comes to assessing whether we are eating correctly.

It is convenient to finish this article remembering something exposed in the first paragraphs: the physical definition of work in which ‘Work = Mass × Acceleration × Distance’. Stated like this, mathematically, we noticed that if the acceleration and the distance remain constant, the work and, therefore, the expenditure of energy, scale approximately 1:1 with the mass. Now, do we really think that someone weighing 100 kilos can maintain the same acceleration and travel the same distance as another person weighing 70? Before answering quickly, the truth is that yes, because there are people who weigh 70 kilos completely sedentary and NBA players who weigh more than 100 kilos and are fast and explosive elite athletes. Knowing how to assess all these factors is complicated, which is why it is not always a question of ‘less plate and more shoe’. The best recommendation that can be given is that you use these estimates to understand that it is not a simple equation and that for a reason there are professionals that should be called upon to do things right.

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