Eating until 85% satiety helps avoid postprandial fatigue caused by the redirection of blood flow to the digestive system during overly large meals.

noli's read

The idea that consuming large volumes leads to fatigue is a well-known phenomenon, often linked to the parasympathetic response and glycemic fluctuations rather than a simple 'redirection' of blood. Studies, such as those published in 'Nutrients' (systematic review), confirm that carbohydrate-rich and high-calorie meals induce more pronounced postprandial somnolence. The concept of 'Hara Hachi Bu' (eating to 80%) is an ancestral practice supported by observational evidence on longevity, although the precise mechanism is multifactorial (hormonal, nervous, and metabolic). The explanation centered solely on blood flow is a simplification, as the body effectively manages blood perfusion to the gut without significantly depriving the brain. The approach remains an effective behavioral strategy for energy management, even if the biological mechanism is more complex than a simple redistribution of blood volume.

the sources

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