You have probably heard people say things like "It's not healthy to lose weight too fast, as it'll make your metabolism stall" or "Your body will go into survival mode" and such. These statements are neither completely true nor false. Let's start by getting one thing out of the way first. The rate you burn calories will never just stall.
What is the Metabolism?
Metabolism is a term that collectively describes how your body converts and uses energy. There's a difference when talking about metabolic hormones, and metabolism in general - the latter referring to your body's ability to burn energy. Most people have probably heard, or even thought themselves "I'm overweight because I have a low metabolism" or "You can eat anything you want without gaining weight! You must have a high metabolism." Metabolism is often referred to as a part of our biological make-up that regulates how fast or how slow we burn calories. But the metabolism is so much more than that. Metabolism is all chemical reactions that occur in the body; all the hormones, brain cells, intestinal cells, and fat cells that regulate our health, aging process, body weight, and how we burn calories.
When we talk about having a high or low metabolism - or when we talk about something being wrong with the metabolism, it's usually in relation to imbalances in the regulation of thyroid hormones; a metabolic disease. If you think you might have a metabolic disease you should see your doctor, as such a disease can influence many aspects of your body. Even though you feel like you gain weight as soon as you even look at a piece of cake, it's quite rare that this has anything to do with the metabolic disease - or an imbalance in your metabolism.
How the Metabolism Works
The human metabolism consists of three parts, which all have an influence on your body’s energy conversion.
1. Resting Metabolic Rate/Basal Metabolic Rate
We can call this our "idle energy consumption". This is the amount of energy your body needs to stay alive when you are idle or resting. The resting metabolism is affected by age, gender, and body weight, as well as how these aspects relate to your genes. The resting metabolism normally amounts to approx. 50-70% of the total calories your body burns.
2. Food-Induced Metabolism
The energy your body uses to metabolize the food you consume. How much energy is used is dependent on what you consume. There are some foods that the body uses more energy to convert than others (e.g. proteins), while others require almost no energy to metabolize (e.g. refined sugar).
3. Physical Activity Level
This is the part that varies most depending on activeness. A carpenter or tradesperson would, for example, burn a lot more calories than someone working in an office, as the former spend the day doing hard physical labor. Yet all activity increases the number of calories burned. Even small things like tapping on your desk with your fingers while you're waiting for something. The more you move, the more calories you burn. Depending on how active you are throughout a day, your physical activity accounts for approx. 20-40% of the total amount of calories burned that day. If you consume more energy than you use, then your body will store this excess energy in your fat reserves to be used later; i.e. you gain weight. This is known as a caloric surplus.
If you consume fewer calories than you use, your body will take from your fat stores; i.e. you'll lose weight. This is known as a caloric deficit. To maintain a normal weight, you must maintain an energy balance. This means that you must consume about the same amount of energy that your body uses.
Can Your Metabolism "Stall"?
During weight loss, there will undoubtedly be some metabolic changes. That said, people's understanding of the metabolic process isn't always in line with reality. Even under conditions where the body experiences extremely low energy consumption (and as such quick weight loss), such as on a VLCD (Very low-calorie diet) like the Nupo Diet, the body's metabolism will never "stall". Back in 1945, there were studies conducted where a group of 32 men was subjected to a calorie deficit of 55% (approx. 1500 daily calories). Simply put, they had their normal calorie intake halved for a period of 24 weeks. When the experiment concluded, all the participants had, on average, reduced their body weight by 25%, and their body far percentage had fallen to 5%. Additionally, the studies showed no signs that their metabolism had stalled, and there were no signs of their bodies entering any sort of "survival mode".
Read more: what is the Nupo Diet?
But then why is it that you might have a hard time losing weight, even if you are consuming few calories and maybe even being physically active every day? It's usually a combination of three things:
Change in Body Weight
When you lose weight, you won't be moving around as much mass as did before your weight loss. As such, you won't be burning as many calories doing the same daily activities and workouts as you did previously. With a reduced mass, your body now requires fewer resources to keep your body running. Therefore, it's important to adjust your calorie intake and physical activity to maintain your weight loss. You'll need to consume fewer calories and maintain your energy balance.You are Subconsciously Doing Less
After a longer period on a tight diet, experiencing weight loss, and reducing your calorie consumption, it's completely normal to feel worn out. Maybe you've even started working out. Perhaps you've doubled your cardio over the last 4-6 months, and maybe you've reduced your daily calorie count by 500-1000. Despite feeling like you are doing more, your total physical activity may have dropped. NEAT(Non-exercise activity thermogenesis) is everything that you do outside of the gym; going to work, fetching coffee, cleaning, grocery shopping, walking the dog, laundry, etc., and if you are far along on your weight loss journey, you will probably be subconsciously less active - regardless if you are working out at the same time. Your net gain regarding your physical activity outside of the gym (NEAT) will therefore fall drastically. This type of physical activity, as mentioned earlier, accounts for between 20-40% of your total energy consumption, which means this is one of the factors to keep an eye on. A step counter can be a great tool here.Adjustments in Your Metabolism
As we covered earlier, your metabolism can't "stall". But it can certainly adapt to low energy consumption and high activity levels. The quicker you lose weight, the quicker these adjustments will take place. Your body will become more and more effective when converting and using the energy you need, and you will often see major hormonal changes in people who are, or have been, in the process of losing a lot of weight. These adjustments are inevitable. You can use techniques to keep these adjustments down, yet these techniques include breaks from your diet and/or slower weight loss.
These three points are all related and it's important to understand these processes when you have a greater weight loss goal in mind. Manipulating things like the aforementioned NEAT (your daily physical activity) can have very positive effects on your weight loss and can also ensure steady progression regarding your weight loss for a longer duration of time. Before you label yourself as someone with a "poor" or "slow" metabolism, think about the first two points, and consider what you are eating on a daily basis. We know that people aren't always the best at guessing how much we eat, or self-tracking in general, so it's always a good idea to set aside a few days where you write down everything you eat and drink, and how much. Not for the sake of others, but for your own sake. You are probably eating vastly more than you think.
