Today, the internet provides an enormous amount of fitness information. With this comes information chaos, making it increasingly difficult for ordinary people to navigate. The most chaotic information often involves fat burning and weight loss.
Some mistakenly believe the calories burned by a smart watch mean those calories have left the thighs or abdomen. However, burning calories does not mean they come from fat tissue. Even those that do may not mean we have lost fat.
What is fat burning?
Adipose tissue mainly stores energy for a rainy day. Fat burning is a necessary process that helped us survive periods without food in the past.
To use fats, we must get them out of adipose tissue (mobilise), burn them (oxidise to form energy), and store what is not used back in the tissue.
Enzymes like Hormone-Sensitive Lipase (HSL) or ATGL mobilise fats from adipose tissue. They release free fatty acids. A large part goes to the liver, where they combine into triacylglycerols (fats) and are packed into lipoprotein particles (VLDL, LDL, HDL).
These particles then provide fatty acids for muscles and other organs.
Burning fatty acids, or their oxidation, occurs in the mitochondria. These are the main energy centres of cells. They act as small power plants, without which cells would lack energy. Fatty acids are carried into mitochondria as a complex with carnitine.
Carnitine acts as a converter for fatty acids. In mitochondria, beta-oxidation breaks down fatty acids and produces ATP, which fuels biochemical processes. Glucose or amino acids can also produce ATP, depending on current energy needs.
If there are too many fatty acids, some of them can go back and be stored as body fat again.
Fat burning means using the energy stored in fats. However, the body can also use energy from carbohydrates and proteins. Ideally, we would use only fat reserves. In reality, all energy sources are used.
Thus, calories burned do not always come from fat stores.
Sometimes the body burns fat constantly. For example, the keto diet minimises carbohydrate intake, forcing the body to use mainly fats. Yet even during a keto diet, if energy intake is higher than what is used, fat burning will not lead to fat loss.
Why does fat burning not automatically mean weight loss?
Mobilisation and oxidation of fats happen constantly. The same is true for redepositing fats back into adipose tissue. If there is excess energy, more fat is stored than burned.
This means that burning calories during exercise may not cause weight loss. Without a calorie deficit, we will not lose weight. We will maintain or even gain weight.
How to effectively reduce weight?
The first rule for losing weight is to ignore magic diet pills, quick fixes, and crash diets that promise big results fast.
Effective fat burning is only one aspect of weight reduction. Fat burning is part of caloric expenditure. Caloric intake energy from food is the other side. If expenditure exceeds intake, weight loss occurs because the body uses stored energy, including fats.
If intake is greater, the excess is stored, often as fat. The core principle is a calorie deficit. Fat burning and actual fat loss are not the same.
Weight loss should not be too drastic. No extreme diet works long-term if it is not sustainable. The body remembers its fat levels and tries to maintain them, even when they are too high. Healthy weight loss is not as simple as it seems.
Not every pound gained or lost is fat
If, after losing weight, the scale does not change, do not be upset. Regular strength training and a calorie deficit help build muscle mass. Stronger muscles keep more glycogen and water. The scale may not reflect decreased body fat.
Be cautious about initial weight loss. Daily weight changes mostly show water changes. Morning weight will differ from evening weight. These fluctuations are greater for women during the menstrual cycle.
Common mistakes when losing weight
Moderate intensity aerobic exercise burns the most fat. This leads many people to spend long hours on cardio. However, this only causes weight loss if a long-term calorie deficit is maintained. Otherwise, burned fats are replenished with the next meal.
Another problem with counting calories is that, on average, we write down 30% less than we really eat. This can make it seem like we are in a calorie deficit when we are not. Most people actually eat 30% more calories than they think.
Consistency matters most for weight loss. Drastic diets cause rapid weight regain, called the “yo-yo effect.” The body reacts by increasing hunger and reducing movement. Sustainable weight loss comes from setting achievable habits and allowing the body to adapt to a new weight.
The best approach combines strength training, cardio, and daily activity. One gym session cannot offset sitting for long periods. Taking more daily steps, along with exercise and a calorie deficit, leads to lasting results.
Conclusion
Fat burning is when the body uses stored fat for energy. However, this does not equal total fat loss. If calorie intake exceeds expenditure, the surplus is stored as fat. Body fat is only lost when calorie expenditure is greater than intake.