Welcome back to this series on figuring out why exactly you are not seeing the weight loss you want to see on your low calorie diet. If you have not read the first part, go give that a read through and then come back here so this all makes sense.
Today we will go through the first two reasons you are not losing weight on your low calorie diet. Keep in mind these are going to go in order of most to least likely (so, by #7, we will be getting into the less common, albeit still important, explanations). That said, I have only identified these seven because they are all common to some degree, meaning we could probably write an entire encyclopedia on this topic and come up with seven hundred reasons, but these seven are the most likely culprits.
Before diving into these first two, ask yourself some questions. And seriously reflect on these before moving on.
Why do you want to lose weight? What will this bring you? Could you achieve the things you want out of weight loss (i.e. happiness, self-confidence, impressing others) through any other means? I don't mean to discourage you from your goal but rather to ensure your head is in the right place. I cannot begin to tell you how common it is that someone believes once they lose weight and get to a certain physique that only then will they feel happy and confident, but lo and behold, they get to that weight, it becomes the new normal, and they are no better off.
What do you consider "not losing weight"? Are you dropping one pound a week but don't consider that "enough"? Are you not actually weighing yourself but rather going off what the mirror indicates? We will touch on this again in the next installment, but begin to make sure you are not placing undue expectations on yourself.
Reason #1. Your definition of "low calorie" is off
The first area to look at would be your definition of “low calorie.” Between two individuals of the same gender, height, and weight, 1500 calories could be seen both as “a lot” and “hardly anything.” If you have a large appetite, chances are your threshold for “low calorie” is a bit higher than most.
If this is the issue at hand, your overall approach to weight loss could probably stand to be improved. Gauging a subjective “low calorie” intake implies little to no hard data went into the decision to eat, say, 1500 calories a day. This decision should be based off one of two means of determining your daily calorie expenditure: using a free online TDEE calculator, or spending a period of time tracking your food intake and measuring average calorie intake up against average change in weight (what I do with my clients). That way, figuring out how many calories it will take to get to your desired body weight will be based on scientific realities and not subjective guesses.
Reason #2. Your macronutrients (and other extracaloric factors) are off.
On the simplest level, though it might sound silly to some of you, the issue could simply be that you are tracking your calories but not your macronutrients. The macronutrients include protein, fat, carbohydrates (with fiber arguably belonging to a different group), and alcohol. Each of these has a specific number of calories in every gram.
But another important distinction is the physiological response to and storage of these nutrients. Protein, for example, will preferentially be used to maintain the amino acid pool in the body and rebuild muscle. Fat, on the other hand, will be stored directly as body fat (or, less commonly, as intramuscular triglycerides). And carbohydrates will first fill up liver glycogen stores and then muscle glycogen (glycogen is just the human storage form of glucose). Carbohydrates (in the form of glucose) can be converted into fats, but this is much less common than you might imagine (this is another story for another time).
Since these macronutrients have different roles and supply different tissues, there are different downstream effects regarding weight changes. Again, weight change is entirely dependent on an energy imbalance. However, that energy imbalance can be affected by nutrients in indirect ways.
For example, all else being equal, protein preferentially goes to rebuild muscle tissue. Muscle tissue is more metabolically active, meaning if you are proportionally more muscular than someone else at your same weight, you will probably have a higher resting metabolic rate (excluding the extraneous confounders, like thyroid differences). My own research into this showed me that the difference is not nearly as big as we make it out to be, but there are other important consequences to this (improved EPOC, better capacity to train with loads that actually allow for muscular growth, etc.).
As well, muscular contraction can override the glucose transporter found on myocyte membranes, such that glucose is accepted into the cell without even needing the approval of insulin (this is a remarkably important reason for Type 2 diabetics to be regularly exercising).
This also presents important considerations for [anti-]nutrients like dietary fiber, the insoluble version of which may impede nutrient absorption (meaning 500 calories, for example, is processed as 450 calories), as well as non-nutritive sweeteners, resistant starches, and more.
To make a long story short, 2000 calories a day composed of 80% carbohydrates, 10% fat, and 10% protein will elicit a completely different response than that same caloric load composed of 40% carbohydrates, 20% fat, and 40% protein (this is a random figure). Generally speaking, we want to aim for a high protein diet in most populations. Any risk of the kidneys being unable to process a certain upper limit of protein intake is largely unfounded; you can rest assured knowing the kidneys are extremely efficient at what they do, and to be unable to process high levels of protein intake (unless, of course, we are dealing with astronomically high intakes that would hardly even be physically acceptable to the taste palette or GI tract) would be a gigantic stain on human evolutionary progress. The guideline of 0.8 to 1g protein per pound of lean body mass (aka your body weight minus any fat mass) is probably going to be a good range for most people.
For next time
In the next installment, we will go through the next two common reasons for a failure to lose weight on a low calorie diet. What you should take away from today's piece is that the first two places to look when trying to figure out what's going on will be A) how objectively you are defining "low-calorie," and B) where those calories are actually coming from.
Stay tuned for more!