I was reading this interesting piece of research by Sarah Kleiner:

The internal clock of the digestive system reveals that WHEN you eat may be just as important as WHAT you eat.

Circadian Rhythms and Digestion:

Your digestion follows a 24-hour internal clock, known as the circadian rhythm.

This rhythm is influenced by LIGHT exposure and controls:

- Stomach acid secretion

- Digestive enzyme release

- Nutrient absorption

- Gut microbiome activity

(Source:

Digestive enzyme release, gut motility, and absorption follow circadian timing (PMID: 30874451))

How Digestion Varies Through the Day:

- Late Morning: Stomach acid peaks → helps break down protein and absorb minerals.

- Midday: Digestive enzymes surge → more efficient breakdown of carbs and fats.

- Afternoon: Microbiome activity increases → boosts fiber digestion and short-chain fatty acid production.

- Evening/Night: Digestive processes slow down, leading to:

- Poor digestion

- Increased fat storage

- Higher chance of acid reflux, especially if eating close to bedtime

(Sources:

Gastric motility is slower in the evening (PMID: 21342212)

Melatonin, secreted at night, influences gut lining and digestion (DOI: 10.2174/1381612013397681))

Scientific Backing:

Sarah references several studies supporting the importance of meal timing:

Digestive processes are circadian-regulated

➡️ PMID: 30874451

Obese women had better metabolic outcomes when they ate earlier in the day

➡️ DOI: 10.1002/oby.20460

Gut microbiome composition shifts by time of day and light exposure

➡️ PMID: 31689582

Melatonin at night impacts digestion and gut health

➡️ DOI: 10.2174/1381612013397681

Gastric motility slows in the evening

➡️ PMID: 21342212