Welcome to Part 1 of an exciting new series I've concocted to help you figure out why exactly you are not losing weight on your low calorie diet. We will begin the series with an introductory post today, explaining how weight loss works, briefly, and which components in the system might be going awry. We will then get into the seven reasons starting in the next installment. So sit back and enjoy!
What is weight loss?
Changes in weight are the result of an imbalance in the energy input versus output system. Think about it like this: When we say “weight,” what exactly are we talking about? First and foremost body fat, then muscle tissue, then body fluids, undigested food and not-yet-excreted waste, bone weight, and then tissues of other organs (the liver, kidneys, pancreas, heart, brain, diaphragm, etc.).
When we say “lose weight” (or “gain weight”), from which of these sources are we losing (or gaining) that weight? The primary areas will be body fat, muscle tissue, and body fluids.
Body fat is composed of cells called adipocytes, while muscle tissue is composed of cells called myocytes. Both of these groups of cells will readily accept substrate, in the form of ingested nutrients, once they are broken down to their smallest level.
And as we feed the body more substrate, it primes the system to accept more substrate, generally meaning we increase fat stores. As we feed it less substrate, it realizes it cannot continue to rely solely on incoming nutrients for energy, and so it must eventually use up some of its own (for our purposes, this is in the form of fatty acids, which will be mobilized and then oxidized for energy).
So, to bring this full circle, when the body is receiving less energy than it uses in a day, it starts burning some of its own stores to make up for that energy. That is how we lose (or gain) weight.
The key to it all: Your body's caloric needs
The second point we must be clear on is the idea of one’s total daily energy expenditure (TDEE), and what components make it up. TDEE is just another way of saying, “How many calories does your body burn in a typical day?” It is such a useful figure because we use it to arrive at the caloric intake appropriate for one’s weight goal.
If we want to understand why we aren’t losing weight on a given caloric intake, we need to understand what goes into this system and how to get it to favor the weight loss we are looking for. Because at the end of the day, we are dealing with the body’s energy input and output system when considering weight changes, so there is no use in looking to unrelated strategies (herbal supplements, “which” foods to eat, “which” exercises to do, etc.).
This will be short and painless, so just power through this so that the rest of the series makes sense and you can fancy yourself a bit of a diet wiz, if you’d like.
1. Basal Metabolic Rate
The first and biggest component of the TDEE is known as your basal metabolic rate (BMR). You may also have heard this called the resting metabolic rate (RMR); the only difference is in testing protocols, so don’t pay that much mind.
Your BMR tells you how many calories your body runs through on its own each day. You can think of this as the amount of calories you would burn in one day if you were in a coma. It encompasses a wide range of physiological processes happening all the time without your conscious awareness: osmotic regulation makes up the largest chunk of this, but there is also heart contractions, lung/diaphragm expansion and compression, and miscellaneous cellular processes to consider.
Your BMR makes up around 50-75% of your TDEE, meaning a large part of how many calories you burn each day is totally outside of your conscious control. Bummer, right? Not really; I reckon few people would be interested in having to consciously think about breathing at all hours of the day in order not to die.
2. Thermic Effect of Feeding
Next we have what is called the thermic effect of feeding (TEF), also called the thermic effect of food or the thermic effect of eating. Basically, although ingested food obviously supplies us with a set number of calories, it also takes a set number of calories to grind up, swallow, metabolize, and excrete this food.
As you can imagine, this makes up only a small percentage of your TDEE - about 10%, give or take. While this can be manipulated to some extent (taking more time to chew foods or ensuring delayed gastric emptying so that all foods can be fully metabolized at an appropriate rate), we would be dealing with minuscule figures here, so it wouldn’t be worth your time. In other words, TEF as a whole makes up 10% of your TDEE, but the percentage of that that you can actually voluntarily manipulate is bordering on insignificant.
The third and final (excluding NEAT) component is exercise. While exercise only makes up on average 10% of your TDEE, this number can go up or down to some degree depending on how sedentary or active you are.
But ultimately, what all of this information boils down to is that there are two major ways to manipulate energy expenditure (and therefore weight): through food intake or through exercise.
For next time...
That necessary preface sets us up to address the commonly voiced concern that an individual is eating a low calorie diet, yet is not actually losing weight. This can be frustrating at the most basic level, because for those on already considerably low caloric intakes, the idea of having to lower your calories even further can be extremely disappointing or even just not feasible.
In the next post in this series, we will dive straight into why this is happening and how to fix it. If this scenario describes you, rest easy knowing I can guarantee you that one (or more) of the following seven factors is to blame.