Obesity from poor fat burning?

The so-called metabolic flexibility plays an important role in the source from which the body derives its energy. Inflexible metabolism during sleep appears to burn more carbohydrates than fat and favor obesity.

The human body can switch metabolic energy sources in response to changes in nutritional status. During the day, carbohydrates, fats and proteins are broken down by metabolism. Most of the energy comes from carbohydrates right after a meal, while most of the energy comes from fat after fasting, according to experts at the University of Tsukuba from the results of the latest study. The corresponding study was published in the specialized English-language journal.temper nature“is reading.

What is metabolic flexibility?

The researchers said the body’s ability to switch metabolic energy sources in response to changes in nutritional status, such as after meals and during sleep, is known as metabolic flexibility.

Diseases caused by poor metabolic flexibility

Disturbed metabolic flexibility is associated with diseases such as obesity and diabetic, Connected. In the new study, the metabolism during sleep was examined in particular.

“We were interested in how metabolism changes during sleep and whether we could detect differences in metabolism in people with inflexible metabolism,” study author Professor Kombe Tokuyama explains in one of the studies. press release.

What is used as an energy source?

The team used a measure called the respiratory quotient (RQ) as the primary method of investigation. This is the ratio between carbon dioxide (carbon dioxide) and O2 (oxygen) gas absorbed by the body. If the two amounts are the same (RQ is 1), this indicates that the source of energy is carbohydrates. If the ratio is lower (about 0.8), on the other hand, this indicates that fats or proteins are used as an energy source, experts explained.

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In order to characterize changes in metabolism over time, the researchers measured the ratio of carbon dioxide to oxygen for a total of 127 people every five minutes over a 24 hour period.

Is sleep a period of fasting?

Give asleep Indeed, similar to a period of fasting, the team said, one can expect RQs to decrease throughout the night, indicating that more and more fat is being burned as sleep progresses.

Instead, experts found that RQ values ​​drop steadily at the onset of sleep, but rise again after reaching a low point after midnight and continue to increase until awakening.

The participants were then divided into two different groups, depending on how fluctuating their RQ values ​​were. The researchers explained that a higher variance means that metabolism is flexible and that RQ values ​​rise and fall according to the body’s need for them during the day.

Double fat burning thanks to inflexible metabolism

After dividing the participants into a flexible group and a metabolically inflexible group, the team finally found that although the 24-hour average RQ values ​​were the same between groups (plus age, BMI, and body fat percentage), RQ values ​​at night were higher in participants with the least flexible metabolism, indicating that these people burn more carbohydrates than fats.

Prevention of obesity and diabetes

Experts believe that it is precisely these findings that could be very useful in the future, since diseases such as obesity and diabetes are much better prevented than cured. Professor Tokuyama added: “Annual checkups, which focus on measuring RQs during sleep, can help identify people at risk for metabolic disease and enable timely interventions.” (as)

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Author and source information

This text complies with the requirements of the specialized medical literature, clinical guidelines and current studies and has been examined by medical professionals.


  • Simeng Zhang, Yoshiaki Tanaka, Asuka Ishihara, Akiko Uchizawa, Insung Park et al: Metabolic flexibility during sleep; In: Nature (veröffentlicht 08.09.2021), temper nature
  • University of Tsukuba: A potential indicator of obesity risk detected during sleep (veröffentlicht 08.09.2021), University of Tsukuba

important note:
This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. It cannot replace a visit to the doctor.


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