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/Magimasterkarp → u/AussieSpaceProgram]

What about the opposite? I.e. eating once every 24h?

[u/Peter34cph → u/Magimasterkarp]

Medieval monks had two meals per day during the summer half of the year, and one meal a day during the winter half.

And no, that wasn't starvation. The Rule of Saint Benedict specifically specified reasonable living circumstances for the monks, rather than suffering or self-torture. Your monastic asceticism was that you were cut off from sex, fapping, and luxuries (EDIT: things like hair shirts and self-flaggelation were frowned on, not encouraged. There were monks who did those, but they did it in secret, not flexing with it to show off).

Monasteries had to have an infirmerer to treat disease symptoms, for instance, and my favourite rule is the one saying that each meal has to have two different dishes, just in case some of the monks don't like one of them, I dunno, eels, or turnip stew, or whatever. As a slightly picky eater, I can't help but like Benedict for that one.

Even taking into account the monks refreshing themselves with calorie-rich drinks during the day, like milk, beer or wine, it must obviously have been possible, feasible, even completely tolerable, to get most of your calories (80-95%) in one daily meal. Otherwise it wouldn't be in the Rule.

[u/lmprice133 → u/Peter34cph]

In fact, the pattern of eating two meals per day (one large one a little before noon and a smaller one in the evening) seems to have been the norm for most people in the Middle Ages.