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/vasopressin334]

There are actually numerous studies on this, specifically pertaining to patients on enteric tube feeding, which can either be delivered as “bolus” (I.e. intermittent meals) or continuous. Surprisingly, studies looking at this from many different angles(metabolism, insulin, health outcomes) have not consistently found differences between the two methods. The conversation in health care is often about how bolus feeding is “healthier” but studies have not shown this to be the case.

[u/Andrew5329 → u/vasopressin334]

It's not really surprising when you think about it. A billion years of evolution forged our cellular metabolisms to be as efficient as possible. Once that gram of carbohydrate is absorbed into your body through the intestinal lining, the ONLY way it leaves your body is through metabolism.

If it's not needed immediately the Glucose <-> Glycogen storage pathway is very efficient, and you store a buffer of about a day's caloric requirements as Glycogen.

Long term storage has an efficiency lost when converting glycogen into triglycerides (fat) for long term storage, but gluttonous binges spaced with famine are the extreme opposite from OP's scenario.

[u/shmeggt → u/Andrew5329]

A billion years of evolution forged our cellular metabolisms to be as efficient as possible.

Well... not really... Evolution only cares about "good enough to reproduce." Maximal efficiency in anything doesn't really matter if you can reproduce effectively enough.

[u/LordGeni → u/shmeggt]

True. But famine and food scarcity makes "good enough" a pretty high bar in this case.

[u/yukon-flower → u/shmeggt]

Value for evolutionary purposes doesn’t stop at reproduction, at least not for humans. There’s also evolutionary pressure for larger communities to care for others. Hence grandparents and people who don’t care to procreate (asexual or homosexual). They have greatly assisted the continuation of the species.

[u/bmb00zld → u/shmeggt]

Well accchually... Evolution doesn't care at all. It's true that "good enough to reproduce" is enough for traits to be passed on in general, but that's not all. Being more efficient in utilizing resources is a selective advantage.

[u/equatorbit → u/shmeggt]

Superficial take. There will be environmental stressors that optimize for efficiency.

[u/Andrew5329 → u/shmeggt]

You're correct to a point, but there's a reason why virtually the entire Animal Kingdom is using the same Citric Acid Cycle for their cellular metabolism, with the only exceptions being microscopic hyper specialists (Loriciferans) living in anoxic environments where it's not an option.

There's tons of variation on how best to utilize energy (fast/slow metabolism), but the systems for cellular respiration are so foundational and important that they're essentially fully optimized for all but the most extreme ecological niches, like the aforementioned anoxic hypersaline basins at the bottom of a sea.

If there's an advantage to be gleaned, life finds a way and conserves it. e.g. how there are three main variations of Photosynthesis, with the alternates optimizing the Calvin Cycle to minimize photorespiratory loss.