Ray Peat on Fasting

Short answer: Ray Peat did not write an article on fasting, but his articles treat going without food as a stress. He describes the night as a fast that raises cortisol and adrenaline, and he explains the benefits of caloric restriction by what it removes, not by the hunger itself.

What Ray Peat wrote about fasting

He describes the morning as the end of a stress. After a night without food, cortisol and adrenaline are holding the blood sugar up. Breakfast lets them fall, because food takes over that job. Source: TSH, temperature, pulse rate, and other indicators in hypothyroidism

He names exercise on an empty stomach as a specific problem. Running or working before breakfast produces lactate and ammonia and is likely to increase the absorption of endotoxin from the intestine. Source: Lactate vs. CO2 in wounds, sickness, and aging; the other approach to cancer

He cites a rat study in which oxygen consumption fell by 15% on the first day of fasting and by another 15% on the second. Metabolic rate drops quickly without food. Source: Sugar issues

He points out that during stress or starvation animals lose lean tissue faster than fat. Source: Gelatin, stress, longevity

On caloric restriction, he agrees that it extends life in many species, but notes that the restricted animals keep the high metabolic rate of youth. He attributes the benefit to slower accumulation of unsaturated fats and less of certain amino acids. Source: Unsaturated fatty acids: Nutritionally essential, or toxic?, Gelatin, stress, longevity

He notes that restricting only tryptophan, or only cysteine, extends lifespan more than restricting calories, which is one of his arguments for gelatin. Source: Gelatin, stress, longevity

What he suggested in practice

• Eat breakfast, and do not train before it.
• Orange juice at bedtime and on waking, to shorten the night's fast.
• Gelatin with meat, which lowers the share of tryptophan and cysteine without eating less.

Where he wrote about it

This topic comes up in 32 of the articles on his site. These are the most relevant ones:

• Sugar issues · original on raypeat.com ↗
• Glycemia, starch, and sugar in context · original on raypeat.com ↗
• Gelatin, stress, longevity · original on raypeat.com ↗
• TSH, temperature, pulse rate, and other indicators in hypothyroidism · original on raypeat.com ↗
• Unsaturated fatty acids: Nutritionally essential, or toxic? · original on raypeat.com ↗
• Tryptophan, serotonin, and aging · original on raypeat.com ↗
• Stem cells, cell culture, and culture: Issues in regeneration · original on raypeat.com ↗
• Bleeding, clotting, cancer · original on raypeat.com ↗

My take

I am against routine fasting. It can be an OK tool for gut symptoms, but a 48 to 72 hour fast shreds your thymus, and skipping breakfast tells your body the environment is bad.

Quick answers

Did Ray Peat recommend fasting?

No. His articles describe going without food as a stress that raises cortisol and adrenaline and lowers the metabolic rate. He recommends breakfast and warns against exercising before eating.

What did Ray Peat say about caloric restriction?

He wrote that its life-extending effect can be reproduced by restricting single amino acids such as tryptophan or cysteine, and that restricted animals keep a youthful, high metabolic rate.