Metabolism is the sum of chemical work that keeps an organism alive: burning fuel, building tissue, clearing waste, making heat and CO2. Here it means oxidative respiration first, not a calorie spreadsheet.

Oxidative core

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Thyroid hormones set the pace of oxygen use. Sugar and protein feed it. PUFA free fatty acids and stress hormones slow or divert it toward lactic acid and tissue breakdown. Protective CO2 rises when oxidation is real.[1]

See Thyroid, Glucose, CO2, Mitochondria, Stress.

Path of carbohydrate oxidation

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Useful oxidation of sugar is a chain, not a single switch. Rough order:

  1. Glycolysis in the cytoplasm: glucose → pyruvate (small ATP; under stress or blocked mitochondria, more lactate).
  2. Pyruvate dehydrogenase (PDH) at the mitochondrial gate: pyruvate → acetyl-CoA for full aerobic burning. Blocking PDH shifts cells toward fat use and lactate. Estrogen is one documented blocker of PDH (and of cytochrome oxidase further down the chain).[2]
  3. Krebs cycle (citric acid cycle): acetyl-CoA oxidized; NADH/FADH₂ generated; CO2 produced.
  4. Electron transport / oxidative phosphorylation: electrons to oxygen; most of the ATP.

If a late step fails, earlier steps back up (e.g. high NADH tends to shut PDH). That is why thyroid, CO2, and intact mitochondria matter more than obsessing over one enzyme name.

Fructose can bypass a free-fatty-acid block early in glycolysis and keep pyruvate available for oxidation when glucose alone is stalled (Randle cycle context).[3]

Common brakes

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These are the recurring anti-metabolic pressures in this framework (not a complete list):

Support pattern: sugar oxidation, protein with enough gelatin balance, salt, light, lower PUFA, gut care, thyroid context. See Pro-metabolic, Anti-metabolic, Roadmap.

Practice

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Judge metabolism by temperature, pulse, energy, sleep, and recovery, not only weight. Support food, light, salt, and thyroid context.

Left unsupported, this decline is large and continuous, not a late-life event: "From puberty to old age, oxygen consumption decreases by about 70% unless you intervene. This corresponds to the increase in mortality."[4]

See Basal temperature, Pulse, Roadmap, Bioenergetics.

See also

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References

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  1. ↑ Ray Peat, "Thyroid," raypeat.com.
  2. ↑ Ray Peat, quoted at functionalps.com (endotoxin notes).
  3. ↑ Ray Peat, "Sugar issues," raypeat.com.
  4. ↑ Ray Peat, Politics & Science: Questions and Answers I, February 20, 2013.