The number of calories we are advised to take in by BMR or RMR charts are based merely on Averages.
These Basal Metabolism Rate (BMR) or Resting Metabolism Rate (RMR) charts are based on the calculations of basic mathematical formulas such as Harris/Benedict or Mifflin, or some other less-accepted-but-very-similar formula.
There are a great many people who have a lower BMR or RMR than the posted Average. There are also people who have a higher BMR or RMR than Average, but not very many of them choose to hang around in diet websites.
The standard BMR or RMR calculations might … or might not … apply to your individual body.
There is no predetermined calorie number that tells us whether or not we are eating in a deficit, eating at maintenance, or eating a surplus. The resulting changes in our bodies --- over time --- are what define the amount of how many calories our bodies are using as energy.
Here is an article explaining a few Key Definitions that might help some of us avoid becoming confused about Calories, Diet, and Nutrition.
Defining a Calorie Deficit
by Brad Pilon, bodybuilder, author of Eat Stop Eat (Intermittent Fasting)
Eating at a calorie deficit.
From my understanding, by definition this means an amount of food that results in loss of body mass. By this definition you cannot be in a deficit if you are not losing body mass.
You can be eating less, a little, not much, like a bird, and not lose body mass since these are all subjective descriptions of an amount of food, but if you are eating less food than is needed to provide the energy you require to power your daily activities then a loss of mass must occur.
This loss may be masked by fluctuations in bodyweight caused by water or the weight of the food in your digestive track (at least for a little while), but make no mistake, it is the loss of body mass that defines the deficit, not eating below an estimated amount of needed calories. The Loss of body mass is what defines a Deficit.
Eating at maintenance.
The term maintenance can be confusing; it raises the question, maintenance of what?
From my understanding eating at maintenance does not mean maintenance of body weight, but maintenance of function.
When you eat at maintenance all of your body’s daily energy needs are equaled by the energy provided by the food and drink you consume. This includes the energetic needs for muscle growth since the energy needs of protein turnover are part of your basal metabolic rate.
In other words, if you were in some hyper-muscle-growth-mode induced by who knows what, the energy needs of that growth would be reflected in an increase in your metabolic rate. Meaning if you were not eating enough to cover these needs you would be eating at a deficit and loss of body mass would occur.
A good way to think of maintenance eating is an amount of food that does not result in an appreciable loss of body mass or an appreciable amount of body fat gain, since a gain in body fat is how we define a surplus, and a loss is how we define a deficit.
As an example – If you are eating 50,000 calories a day and not gaining fat, congratulations you are still eating at maintenance. If you are eating 8 Calories a day and not losing body mass, congratulations you are also eating at maintenance.
The amount of calories you consume does not determine if you are eating deficit, maintenance or surplus, the changes in your body does. Lack of a Loss of body mass and absence of a Gain of body fat defines eating at maintenance.
Eating at a surplus.
Since a deficit is defined by weight loss, and maintenance is eating to cover all daily metabolic needs, then a surplus is defined as eating an amount of food that surpasses your daily needs (including protein turnover) and thus results in the storage of energy for future use (body fat).
So a surplus (to me) is defined by the accumulation of body fat. If you are not gaining body fat, then you are not eating a surplus amount of food.
If you are gaining body fat (and not just weight, which could be water etc) then you are eating at a surplus (regardless of the number of calories you are eating). The accumulation of body fat defines a eating a surplus amount of food.
Some random predetermined amount of calories does not define whether or not you are eating in a deficit, at maintenance, or in a surplus, the resulting changes in your body are what define the terms used to describe how much you are eating.
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