“I’ve got very slow metabolism”, “You have to eat more to boost your metabolism”, “When you lose weight your metabolism slows down and you stall”… Have you heard these phrases? I have… way too many times, and today I would like to address one simple thing – the fact that there are two meanings behind metabolic rate slowing or boosting. I’ve already made a blog on metabolism in general and I would appreciate if you could check my video on it too, but I will still revisit the key concepts.
What is metabolic rate?
Our bodies need certain amount of energy for virtually anything we do – things like walking, talking, breathing, and even thinking require energy. Even keeping the body temperature constant takes some energy. This energy is derived from breaking down carbohydrates, fats, and proteins also called macronutrients as nutrition is the primary source of them, but we can use some glycogen, body fat or even our own body proteins to get energy when we are in a caloric deficit. The sum of all biochemical reactions occurring in our body is called metabolism, and the total amount of energy we spend per certain period of time, usually per day, – metabolic rate. It’s typically measured in kcal per day (check out my video on calories too) and there are several factors that play a role – things like total and lean body mass, activity level, nutrition, ambience’s temperature and humidity, even emotional state, and medications we take. And here comes the key issue that I want to talk about – since it’s a rate, technically it makes sense to talk about faster and slower metabolism, but in my opinion this terminology becomes very confusing when applied to a whole organism.
The metabolic conundrum
The problem is that when we (or at least I) hear things like faster or slower metabolism, we imagine cells or tissues burning calories faster or slower – say, one pound of muscle tissue burns X amount of calories at rest (10-15 kcal/kg/day or 4.5-7.0 kcal/lb/day), but if you start exercising or moving in general, it becomes more metabolically active and the same pound of muscle burns way more calories per hour than at rest. But in reality, the metabolic rate measures the total number of calories your whole body burns per day and here lies the problem – it’s more than just the metabolic activity that determines the metabolic rate, much more... I would say, there are at least 2 dimensions in which of metabolic rate can change.
Let me give you an elaborate example: Imagine that you have a tanker, and it has a rubber tank of gas on top of it, which can shrink or expand depending on its fuel level. Special edition. That’s your body. As you drive from one place to another you burn gas from the tank and it shrinks or, if you fill it with gas from a gas station, it expands. Since you care a lot about the looks of your tanker you consult with a tanker fitness specialist who tells you the most obvious fact – if you want your tank to shrink you need to use up gas and the more gas you use, the faster it will shrink. In other words, fuel expenditure will determine the size of the tank. Makes sense, right? So, you start driving around more and more and notice that as the tank shrinks your vehicle becomes lighter and it takes less gas per trip or per 100 km. So, the fuel expenditure slowed down, and the tank is shrinking slower. Would it worry you? Or you would understand that since you have a lighter tanker you just lose weight at a slightly slower pace? That’s exactly what happens with your metabolic rate when you lose weight – your metabolism “slows down” as well as your weight loss, but it doesn’t mean that your tissues became slower, it simply means that you have less tissues to support. And just to be completely transparent – there are more changes to your metabolism that occur when you are dieting, but ultimately it never completely stops, not even close. I will go over it in another blog.
Now, let’s get back to our analogy – imagine that you like the feeling of full tank and you go to McPetroleum and fill the tank up to the fullest. And, oh miracle, now as your tanker is much heavier it started to consume much more gas per trip than before. You boosted your metabolism… But now it doesn’t look the way you’d like it to look – it’s quite large and you don’t like its aesthetics. Was it worth it? The same happens when you eat more – you boost your metabolism a bit, in part due to the increased thermic effect of food (TEF), but you gain weight, and it defies the purpose.
My main point is that the relationship between metabolic rate and weight loss is much more complex than it seems at the first sight – when you lose weight, your metabolism might “slow down”, and “boosting” metabolism will not necessarily lead to weight loss. It actually might result in weight gain. The solution to this conundrum is to use metabolic rate as one of two predictors of weight loss or gain with the second one being caloric intake. If your caloric intake is higher than your metabolic rate, you’re in caloric excess and you will gain weight, if you burn more calories that you consume, you will be in caloric deficit and you will burn fat and lose weight. It is that simple!
Metabolic rate is not the only thing that determines your weight loss or gain. If you want to lose weight you need to be in caloric deficit, which is the difference between caloric intake and metabolic rate. And don’t believe the rest – you won’t break your metabolism if you go on a diet, it won’t come to a complete halt after some periods of caloric restriction, and boosting it by eating is counterproductive. You will not lose weight when your caloric intake exceeds your metabolic rate, even if it’s very “fast” and you will lose weight if your metabolic rate is higher than your caloric intake, even if it’s very “slow”. Consistent caloric deficit is the answer!
I hope that you can see how it works and will not let anyone confuse you with catchy slogans. And of course, I hope that here, in my blogs, or on my YouTube channel you will be able to find your inspiration and answers to some of your questions. So, subscribe and feel free to make comments, ask questions, and makes suggestions for future topics. All constructive interactions are welcome!