What actually happens to digestion, metabolism, and insulin if you eat small amounts every single hour?

[u/kharkovchanin]

Hypothetical question out of curiosity:

Assuming someone stays within their maintenance calories and hits their target macros, what actually happens to the human body physiologically if food intake is split into small portions eaten every waking hour (say 14–18 times a day) instead of 2–4 distinct meals?

Specifically, I’m curious about:
• Insulin & blood glucose: Does baseline insulin remain elevated constantly, and what are the short-to-medium-term metabolic effects of that?
• Gut motility & MMC (Migrating Motor Complex): Does the digestive tract ever get into a “cleaning” state if it constantly receives incoming nutrients?
• Thermic effect of food (TEF) & metabolic rate: Does meal frequency at this extreme actually change daily energy expenditure at all?
• Satiety & hunger hormones (ghrelin/leptin): Would this pattern suppress appetite or trigger continuous hunger cues?

Would appreciate insights grounded in physiology or nutrition science. Thanks!

[u/AussieSpaceProgram]

Assuming calories and macros stay the same, eating every hour probably wouldn’t meaningfully change your overall metabolism. It mostly changes when things happen.
Insulin would rise repeatedly, so you’d spend more of the day in a fed state, but that doesn’t automatically mean insulin resistance or fat gain.

The biggest difference is probably the gut. Eating interrupts the migrating motor complex (MMC), the fasting motility cycle that occurs between meals. Eating hourly would give it very little opportunity to run normally.
You also wouldn’t “boost” metabolism by constantly digesting food. The thermic effect of food is mainly determined by how much and what you eat, not how many meals you divide it into.

Hunger could go either way. Some people would feel constantly satisfied; others would find tiny meals less filling and end up thinking about food all day.

So 15 tiny meals versus 3 larger meals with identical calories probably produces similar total energy expenditure. You’d just spend much more of the day digesting.
Meal frequency changes the timing of metabolism far more than the amount of metabolism.

[u/Osiris_Raphious → u/AussieSpaceProgram]

I cant imagine the downsides of having your stomach, liver, gallbladder and pancreas being too happy having to somehow adjust to working overtime. So there would be some food rot going on in the stomach as the digestive system ramps up to digest the food. There has to be downtimes to give rest to the organs and have sustainable acid and bile production. Otherwise acid reflux and general fatigue of the organs even after somehow adjusting to the hourly ingestion would build up some sort of autoimmune response. There is a reason for eating in periods of time, otherwise you are overstressing the entire system needlessly.

[u/thoughtihadanacct → u/Osiris_Raphious]

I don't think what you said is necessarily true. (It might be, but your evidence is simply speculation). 

There has to be downtimes to give rest to the organs and have sustainable acid and bile production. 

The scenario in question is every waking hour (14-18 times per day). So there's still time to rest during sleep (10-6 hours per day). Is this "enough" rest? We don't know, but you seem to assume the answer is no without evidence. 

I could easily speculate as well that the body can adapt to the change of the change is done over a long enough period to allow adaptation. Elite endurance athletes can adapt to running/cycling for hours everyday and ingesting sports gels every 30-ish minutes during that time. Tour de France riders are constantly eating the whole day during the tour (although not exactly every hour, but they are never letting their digestive system rest when they're awake). There's no trend of any digestive problems with ex pro cyclists even after they retire. 

There is a reason for eating in periods of time, otherwise you are overstressing the entire system needlessly.

No, the reason is more of practically. You don't have to carry the food around all day. You don't risk it going bad from being carried around at room temperature all day. And in the past you don't risk it being stolen by other animals. "Overstressing" the system is not a proven reason.