[Attummm]

Whether "burning calories" is used for nutrition or for "burning fat," both terms are common in everyday speech. The rate of "burning" increases during fasting. I have linked one study published in Nature.

Let's go over some excerpts that will answer your questions.

* Metabolism increases during fasting.

> Thus diverse, pronounced metabolite increases result from greatly activated catabolism and anabolism stimulated by fasting.

* The hormone t3 produced by the thyroid is used to control metabolism. In this study they instead looked at markers for actual metabolism.

> We performed non-targeted, accurate semiquantitative metabolomic analysis of human whole blood, plasma, and red blood cells during 34–58 hr fasting of four volunteers. During this period, 44 of ~130 metabolites increased 1.5~60-fold. Consistently fourteen were previously reported. However, we identified another 30 elevated metabolites, implicating hitherto unrecognized metabolic mechanisms induced by fasting.

* The study also mentioned prolonged fasting. Which is earlier stated longer then 24 hours.

> Quantification of blood metabolites from 4 volunteers during prolonged fasting. (a) Experimental procedures employed to study metabolomic changes during human fasting for 58 hr.

[_yb2s]

A metabolomics study like that does not measure metabolic rates, you are fundamentally misunderstanding the article- it has no relevance to this discussion or my statements. They are measuring metabolite concentrations which tell you essentially nothing about metabolic rate. For that people use direct or indirect calorimetry.

[Attummm]

* Metabolite[0]

> In biochemistry, a metabolite is an intermediate or end product of metabolism.

* Metabolomics[1]

> Metabolomics is the scientific study of chemical processes involving metabolites, the small molecule substrates, intermediates, and products of cell metabolism.

[0]https://en.m.wikipedia.org/wiki/Metabolite [1]https://en.m.wikipedia.org/wiki/Metabolomics

[_yb2s]

You can’t be serious

[Attummm]

Metabolomics is the study of metabolism using the latest technology to look directly into cells. Metabolic rate is often measured through oxygen consumption and CO₂ production (indirect calorimetry), but this primarily focuses on aerobic processes and does not provide a complete picture of metabolism. Within metabolism, there are both aerobic and anaerobic energy pathways. Measuring metabolic rate through oxygen consumption and CO₂ production does not account for anaerobic processes such as glycolysis (glucose breakdown), beta-oxidation of fatty acids, and the creatine phosphate system.

Researchers sometimes try to mitigate this limitation by measuring lactate levels in the blood, which can provide some insight into anaerobic metabolism, particularly in muscles. However, blood lactate levels primarily reflect anaerobic glycolysis and do not fully account for other anaerobic processes involving fatty acids and creatine phosphate. There are formulas to estimate these processes, but they are still approximations.

Metabolomics, on the other hand, looks directly into the cells and is not limited to only aerobic processes or anaerobic lactate production. Instead, it can identify and quantify a wide range of metabolites, which are the intermediates and end products of metabolic reactions. Thus, metabolic rate measurements provide an estimate of energy expenditure but do not directly assess the complex metabolic processes occurring within cells, whereas metabolomics offers a more direct and detailed view of cellular metabolism.

As such, the study published in Nature is within the field of metabolism and uses the latest technology to study metabolism directly. Therefor it constitutes our latest understanding of metabolism during fasting.

[layla5alive]

The Dunning Kruger effect is strong! Thanks for trying to explain it to them, I sincerely appreciated your valiant efforts :)