How Long Should One Work Out to Burn Fat Tissue as Efficiently as Possible?
David Janitzek
2026-03-17
4 min. read
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In the fitness community, there are numerous urban legends related not only to training but also to diet. One of them is the belief that in order to effectively burn fat tissue, one should exercise for a certain amount of time, such as 60 minutes. Is this true? How long should one work out to burn fat tissue as efficiently as possible?
When the body starts to oxidize fat tissue
To answer the question of how long training should take to achieve maximum fat oxidation, it's important to look at the human body's physiology. For proper functioning and carrying out daily activities or physical activity, the body always needs fuel, which means that fat tissue is continuously oxidized, to a lesser or greater extent. It cannot be unambiguously determined when the body begins to oxidize fat.
Does the body exclusively utilize fat tissue during physical exertion?
Many individuals erroneously believe that during any type of physical activity, exclusively fat is oxidized, which is associated with fat loss. However, muscles derive energy for work from fatty acids, blood glucose, stored intramuscular triglycerides, and muscle glycogen. The energy source for working muscles is not just fat, but also carbohydrates. It should be emphasized that fatty acids do not always originate from fat tissue. This means that their oxidation does not always result in fat tissue loss. Why does this occur? Fatty acids in the blood can originate from visceral fat tissue, which is located between the internal organs and is found in the abdominal cavity. Visceral fat tissue burns significantly faster than subcutaneous fat tissue, the burning of which is most important for those training. It is this tissue that has the greatest impact on external appearance.
How fat tissue transforms during weight loss
Most people are unaware of what exactly happens to fat tissue during weight loss. R. Meerman and A. Brown conducted a study in which they asked a group of experts, including personal trainers, doctors, and dietitians, what they believed happened to fat tissue during weight loss. Unfortunately, the majority of them were convinced that fat was converted into energy or heat, which is a false theory because it violates the law of conservation of mass. Another misconception concerned the excretion of fat metabolites in feces or their conversion into muscle. In actuality, burned fat combines with oxygen and produces carbon dioxide (CO2) and water (H2O), which means that burned fat is converted into urine and exhaled during exhalation (R. Meerman, A. J. Brown 2014).
Is it genuinely feasible to burn calories while sleeping?
Sleeping is critical for body recovery. The number of calories that can be burned during sleep depends on the individual. Generally, a person can burn between 69 and 91 kcal per hour of sleep, meaning that someone sleeping for 8 hours can burn between 544 and 725 kcal. This energy is sourced from fat tissue and muscle glycogen. However, it is essential that the last meals are not consumed just before sleeping.
Summary
The reduction of fatty tissue is a very difficult and long-term process. It is important to remember that the oxidation of fatty acids derived from fat tissue is very difficult to achieve solely through physical activity, as during exercise the body draws energy mainly from stored intracellular triglycerides. A key aspect in the process of losing excess weight is a diet with a negative calorie balance. Physical activity also serves to deepen the negative calorie balance, which contributes to the reduction of fat tissue. It makes no sense to focus on the fact that a certain physical activity is too short to burn the right amount of calories. It is important to choose an activity that brings joy and satisfaction, so that it is possible to achieve and maintain satisfying results. It is important to remember that overly intense workouts during the reduction of fat tissue can lead to a decrease in NEAT (non-exercise activity thermogenesis). It is important to emphasize that physical activity outside of training is very important in the context of weight loss. Energy expenditure through activities such as tapping, gesturing, cleaning or climbing stairs can create a calorie deficit of 200-2000 kcal. In comparison, energy expenditure during gym training is only 200-400 kcal. It is also important to pay attention to the appropriate amount and quality of sleep. These factors are crucial for the proper functioning of the body. Even during sleep, the body burns calories.
