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Among the dieters, gastric capacity was reduced 27 percent to 36 percent, on average, depending on how it was measured. There was no significant change in the control group.
It’s more lkely to distend your stomach and cause you to gain weight.
So what's the truth? Does it actually cause your stomach to change size? Does it actually reduce your appetite? Is there actually a direct connection between stomach size and appetite?
From personal experience, I'd say that it does in fact seem to reduce your appetite after a while, by whatever mechanism (perhaps stomach physical shrinking, or body simply getting used to it and sending fewer signals, etc). I'd like to see some actual research about this topic, however.
Another anecdote: I was in the hospital a couple of years ago and did not eat solid food for two months. (I was "fed" through an IV.) Once I had recovered enough to eat again, my stomach capacity was very low - I remember having two scrambled eggs for breakfast (and nothing else, hadn't eaten for 8-10 hours) and I couldn't finish them. Obviously I can't say for sure whether my stomach was physically smaller than before or if my body decided to give me the "you're full, stop eating" signal far earlier.
I note that the third link is talking about eating less for one day, which seems unlikely to be sufficient to trigger significant changes in organ size.
Not an answer, but interesting: This study compared bulimics to obese people and it suggests gastric capacity is related to how much you binge, rather than body weight.
Regarding appetite, the mechanism for that as it relates to the stomach (when the stomach is physically stretched, it triggers the body to stop producing the hormone that communicates hunger) is touched upon here: skeptics.stackexchange.com/questions/35330/…
From Huff Post, which references Dr. David C. Metz, a published gastroenterology professor:
Our hypothesis became that [competitive eaters] have the ability to relax their stomachs to such a degree that they can just eat and eat. While eating, the average person's stomach may expand to hold two or three liters, he imagines, whereas a competitive eater's may expand to hold six or seven.
There isn't a lot of research around this, and Dr. Metz's study is one of the most cited studies for competitive eating (according to the Huff Post article).
From this limited information, I can only hypothesize that if a normal person's stomach expands to about three liters and a trained competitive eater's expands to seven liters, it's possible that a stomach can lose some stretching capacity when one eats less food.
Either way, it's important to make a distinction between the size of the stomach and the capacity of the stomach. Even if gastric capacity was reduced (as cited by the OP), that may or may not have any impact on the size of the stomach.
@joulesm: This edit makes it a much better answer for Skeptics. Thank you. However, the problem now is the speculation. I heard (with no evidence!) that when you gain weight you grow more fat cells, but when you lose weight, you don't lose the cells, they just become smaller (allegedly making weight re-gain easier). I don't know if it is true, but it suggests that it isn't sufficient to assume that the process of growing your stomach is bidirectional.
I see your point. Would it be better to remove the hypothesizing paragraph? Or is there a better way to post evidence that doesn't quite answer the question yet? :) I'd put it as a comment on the OP but I don't have global commenting privileges yet :P
