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Thanks to the Internet, there is a lot of information from the world of fitness and with it comes information chaos, which is becoming increasingly difficult for the average person to navigate. Probably the most chaotic information is in the area of fat burning and weight loss. Some of us mistakenly believe that the calories burned that a smart watch shows us mean that those calories have “left” our thighs or belly. However, burning calories does not automatically mean that those calories came from fat tissue. And even the ones that come from it don’t necessarily mean we’ve lost fat.
What is Actually Fat Burning?
Adipose tissue is the main energy reserve for worse times. Burning fat is, therefore, an essential process that has enabled us to survive periods without enough food in the past. However, in order to be able to use fat, we need to get it out of adipose tissue (mobilise it), burn it (oxidise it to produce energy) and store what is not used back [1].
The mobilisation of fat from adipose tissue is due to enzymes such as hormone-sensitive lipase (HSL) or ATGL, which release free fatty acids from fat. A large proportion of these go to the liver where they are reunited into triacylglycerols (fats) and “packaged” into lipoprotein particles (VLDL, LDL, HDL). These particles are then used as a source of fatty acids for the muscles and other organs [2].
The burning of fatty acids, i.e. their oxidation, takes place in the mitochondria. These are the main site of energy production in the cells of the human body. They function as small cellular power stations, without which our cells would not have the energy they need to live. Fatty acids are transported to the mitochondria as a complex with carnitine. The latter acts as a “transporter” for the fatty acids, without which they would not reach the mitochondria. In the mitochondria, the so-called beta-oxidation of fatty acids takes place, i.e. “fat burning”, during which ATP is formed – the fuel for all the necessary biochemical processes in the body. It is still true that ATP can also be produced from glucose or amino acids, depending on the actual energy needs of the body [3].
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In the case of excess fatty acids, mobilised fatty acids can also be stored back into adipose tissue [4].
Thus, burning fat means using the energy found in fat. However, energy is also found in carbohydrates and proteins, which the body can use as well. In an ideal world, we would only spend fat stores, but in the real one, we use all energy sources. So the calories burned don’t have to come from fat stores alone.
There are situations when the body burns fat constantly. An example is the keto diet, during which carbohydrate intake is minimised and the body has to use mainly fat for energy. However, despite the increased fat burning on the keto diet, it is still true that as long as the amount of energy intake is higher than the amount of energy used (calorie surplus), this fat burning will not lead to weight loss from fat stores.
Why Does Burning Fat Not Automatically Mean Weight Loss?
The mobilisation and oxidation of fats occur almost constantly. However, the same applies to the re-storage of fats in adipose tissue. If there is an energy surplus in the body, more fat will be stored than burned. In other words, even after an hour-long treadmill workout, the calories burned may not lead to weight loss. The fact remains that without a calorie deficit, we will not lose weight — we will either maintain our weight or gain it.
How to Reduce Weight Effectively?
The first rule of effective weight loss is to forget about miracle diet pills, quick, drastic diets and other procedures that promise unrealistic and unsustainable results in a short time.
Effective fat burning is only one part of how to reduce weight. Fat burning can be categorised under caloric expenditure. On the other side of the equation is caloric intake, which is how much energy we take in from food. If the expenditure is higher than the intake, we will logically lose weight because the body has to reach for energy stored in reserves (fat). If the balance is reversed and we take in more than we spend, the excess energy will be stored. The main point in weight loss is caloric deficit.
You can also calculate your optimal energy intake in our online calculator, which allows you to plan a tailor-made diet.
Weight loss also cannot be too drastic. No diet, no matter how drastic, will work in the long run if it is not sustainable. The body literally remembers how much fat stores it had and tries to maintain their state even though there was more than necessary. Healthy and sustainable weight loss is not as black and white as it seems. What happens to the body during weight loss and how to prevent rebound weight gain can be found in this article.
Not Every Pound Lost or Gained Is Fat
If the number on the scale does not change despite weight loss, there is no reason to be sad. With regular strength training, during which we maintain a caloric deficit, energy is also used to build muscle mass. Stronger muscles hold more glycogen (glucose stores) and therefore more water. Therefore, the number on the scale does not have to change even though the fat from the body gradually decreases.
Similarly, beware of the premature joy of losing weight. In daily weighing, the given deviation is due to the different water content of the body. Morning weighing will also show a different number than evening weighing. These variations are particularly relevant for women whose water retention is more pronounced due to the menstrual cycle.
Common Weight Loss Mistakes
With moderate intensity aerobic exercise, the most effective fat burning can be achieved. It is because of this that people often choose to spend long hours doing cardio. This only makes sense for weight loss if a long-term calorie deficit is maintained. Otherwise, the burnt fats are replenished again at the first meal we take.
Calorie counting poses another problem – on average, we write down 30% less than we actually consume. Because of this, it may seem that we are not losing weight in a deficit. The truth is that we are consuming 30% more calories than we actually think [5]. This manual can help you track calories more effectively.
The most important factor in weight loss is consistency. If we take the seemingly easy route of drastic diets that last a few weeks, we will quickly put the pounds back on. This phenomenon, referred to as the “yo-yo effect”, is the brain’s natural reaction to the weight lost. It forces us to eat more and move less. To avoid this effect, we need to set up a sustainable weight loss routine so that the brain reprograms itself to the new body weight.
The ideal combination for weight loss is strength training with plenty of cardio (aerobic exercise) and an increase in the amount of movement we do throughout the day. An hour in the gym won’t save us if we sit for the remaining few hours of the day. Higher daily step counts combined with exercise and caloric deficit are the things that produce long-term, sustainable results.
Conclusion
Burning fat does not mean that we will actually lose fat from the body. It is a process in which the body extracts the energy needed for all the important processes to function from the stored fat reserves. However, if we take in more calories than we consume, the excess calories will be stored in fat stores regardless of how much fat we burn.
[1] Moreno, M J, and J A Martínez. “El tejido adiposo: órgano de almacenamiento y órgano secretor” – Adipose tissue: a storage and secretory organ - doi:10.23938/ASSN.0812
[2] Grabner, G.F., Xie, H., Schweiger, M. et al. Lipolysis: cellular mechanisms for lipid mobilization from fat stores – https://doi.org/10.1038/s42255-021-00493-6
[3] Purdom, T., Kravitz, L., Dokladny, K. et al. Understanding the factors that effect maximal fat oxidation – https://doi.org/10.1186/s12970-018-0207-1
[4] Rajjo TI, Harteneck DA, Jensen MD. Direct free fatty acid storage in different sized adipocytes from the same depot - doi: 10.1002/oby.20673
[5] Campus, D. S. (n.d.). Evaluating calorie intake. Data Science Campus Evaluating Calorie Intake Comments. https://datasciencecampus.ons.gov.uk/eclipse/
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